Standards for Electrical Technician Skill Competitions (Questions and Answers)
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:I’m hoping to get everyone’s help – I’m looking for the standards for the electrical technician skills competition (questions and answers). Thank you!
\"Safety Regulations\" and \"Two Types of Forms\" I. Fill-in-the-blank questions: (1 point for each blank, 70 points in total) 1. Workers must take an exam on these regulations (once a year); those who have to stop working with electricity for more than (three months) due to certain reasons must re-study these regulations and pass an (exam) before they can resume work. 2. Electrical equipment with a voltage level of (1000) V or above is referred to as high-voltage electrical equipment ； Electrical equipment with a voltage rating of 1000 V or less is referred to as high-voltage electrical equipment. 3. Electrical equipment in use refers to electrical equipment that is (fully under voltage), (partially under voltage), or (under voltage as soon as it is operated). 4. Whether the high-voltage equipment is energized or not, workers must not (remove it alone) or (cross the barriers) to carry out work ； If it is necessary to remove the barrier, this should be done (with a supervisor present) and while maintaining the safety distances specified in the procedures. 5 Safety distance when the equipment is not powered off: Voltage level (KV): 10, 110, 220; Safety distance (M): 0.7, 1.5, 3.0. 6. During thunderstorms, when it is necessary to inspect outdoor high-voltage equipment, one must wear insulating boots, and should not approach lightning rods or surge arresters. 7. On a work order, the (work order issuer), the (work order supervisor), and the (work order approver) cannot hold these roles simultaneously; the (work order supervisor) may fill out the work order. 8. Switching operations shall be carried out in accordance with the instructions of the (on-duty dispatcher) or (person in charge of operation), after the recipient has (repeated them to confirm accuracy). The command instructions should be (accurate) and (clear), using standard (dispatch terminology) as well as the (dual names of the equipment), that is, the (equipment name and number). The person giving the command and the person receiving it should first (exchange their units and names). Operators should understand the (purpose of the operation) and the (sequence of operations); if they have any doubts about a command, they should (ask the person giving the command for clarification) before carrying it out. 9. The (operator) fills out the (operation ticket) for switchgear operations; each operation ticket can only cover (one) operation task, and the ticket must include the (double name) of the equipment. 10. The operation of switching off power should be carried out in the order of (circuit breaker) – (load-side isolator) – (power-source side isolator), while the operation of restoring power should be done in the (opposite) order. It is strictly prohibited to operate the isolators while the load is still connected. 11. The verification of the position of electrical equipment after operation should be based on its actual location. When the actual location cannot be seen, changes in the equipment’s (mechanical position indicators), (electrical indicators), (meters), as well as (telemetry and remote signaling signals) can be used to determine the position; at least (two) or more such indicators must show corresponding changes simultaneously in order to confirm that the equipment has been moved to the correct position. 12. When testing for electricity, a contact-type voltage tester of (the appropriate voltage rating) and that is (qualified) should be used. Before testing for electricity, it is necessary to first confirm that the voltage tester is in good condition (by testing it on a live device). 13. When installing a grounding wire, connect the (grounding end) first and then the (conductor end); the grounding wire must make (good contact), and the connection should be (reliable). The order for removing the grounding wire is the opposite of this. 14. The organizational measures to ensure safety include: (work ticket system), (work permit system), (work supervision system), and (work interruption, transfer, and completion system) ； Technical measures to ensure safety include: (power outage), (voltage testing), (grounding), and (installing signs and barriers). 15. The neutral point of high-voltage equipment in operation should be considered a (live conductor). 16. In the event of a ground fault in high-voltage equipment, one should not approach the fault site within 4 meters indoors, and within 8 meters outdoors. Persons entering the aforementioned area should (wear insulating boots), and when contacting the equipment’s casing and framework, they should (wear insulating gloves). 17. Once the switch is closed and power is supplied, a sign reading “Do not close – people are working” should be hung on the operation handles of the switches and disconnectors used for the construction equipment. A sign reading “Stop – high voltage hazard” should be placed on the barriers surrounding the live equipment in the area where work is being carried out. II. Short-answer questions: (4 points per question, 20 points in total) 1. Under what circumstances is it possible to perform switching operations without filling out an operation ticket? 1) Emergency handling of accidents 2) Single operation of closing and opening circuit breakers (switches) 3) Opening or removing the only set of grounding switches or grounding wires in the entire station. 2. What operations are permitted using switches when no switches are installed in the circuit? 1. Closing and opening faulty PTs and arresters. 2. Closing and opening the neutral point grounding switch of the main transformer. 3. Closing and opening fault-free unloaded transformers with an excitation current of no more than 2A, as well as fault-free unloaded lines with a capacitive current of no more than 5A. 4. Closing and opening loop balancing currents with a voltage of 10 KV or less and a current of less than 10A. 5. Closing and opening fault-free busbars or capacitive currents directly connected to the busbars. 6. Using outdoor three-pole switches to control loads with a voltage of 10 KV or less and a current of 15A or less. 7. Bypass switches connected in parallel with switches; these can be used to manage the bypass current of such switches when they are in the closed position, but it is necessary to remove the fuse from the control circuit of the switch before performing this operation. 3. What is the sequence for switching power on and off in a single-power supply circuit? 1. The sequence for performing power outage operations is to first operate the switch, then the circuit breaker on the load side, and finally the circuit breaker on the busbar side; the sequence for restoring power is the reverse of this. 2. Before operating the circuit breakers, it is necessary to ensure that the switch is in the open position. Before closing the switch to restore power, it is essential to verify that the circuit breakers are in the closed position. It is strictly prohibited to operate the circuit breakers while there is a load connected. 4. What is the sequence for turning a transformer on or off? 1. For single-power-source transformers, during a power outage, the switch on the load side should be turned off first, followed by the switch on the power source side; then the circuit breakers on each side should be opened in the same order (first those on the load side, then those on the power source side). The sequence for restoring power is the reverse of this.
2. For dual- or triple-power-source transformers: 1) Under normal circumstances, during a power outage, the switch on the low-voltage side should be turned off first, then the one on the medium-voltage side, and finally the one on the high-voltage side; after that, the circuit breakers on each side should be opened. The sequence for restoring power is the reverse of this. 2) In special situations, the sequence for turning the transformer on or off also needs to take into account the configuration of protective devices and the distribution of electrical currents.
5. What are the basic principles of first aid? Active measures should be taken at the scene to save the lives of the injured, alleviate their injuries, and reduce their suffering; depending on the severity of their injuries, immediate contact should be made with emergency medical services for treatment. The hallmark of successful first aid is rapid action and correct procedures, as any delay or mistake can lead to worsening of the injured person’s condition or even death. III. Essay questions: (5 points per question, 10 points in total) 1. Briefly describe the procedure for performing electrical switch operations. 1. Issuing and accepting operation tasks 2. Filling out operation tickets 3. Reviewing operation tickets 4. Issuing and receiving commands for operation execution 5. Simulation operations 6. Actual operations 7. Inspecting the equipment 8. Reporting on the operations and stamping them as “completed” 9. Keeping relevant records. 2. Safety measures in substations during line work. The switching on and off of power to the line must be carried out in accordance with the instructions of the duty dispatcher or the person authorized to work on the line. In the event of a power outage, all circuit breakers, line isolators, and busbar isolators that could cause power to be supplied to the line must first be turned off. The pull-out switches should be moved to the testing or maintenance position. After confirming that there is no voltage present, ground wires should be installed at all points on the line where power might be supplied, or the grounding switches should be closed. Signs reading “Do not close – someone is working on the line” should be attached to the operation handles of both circuit breakers and isolators. Such signs should also be displayed on the screens at the locations where these devices are operated. According to the ‘On-site Operation Procedures’: 1. Fill in the blanks: 1) The model of the main transformer at this station is (SFPSZ10–150000/220); the connection type is (Yn,YN0,D11); the rated voltage is ((220 ±8×1.25 %)/121/10.5); the rated current is 393.6/715.7/4123.9; the rated capacity is 150000/150000/75000; the cooling method is ONAN/ONAF/OFAF. 2) The rated voltage of the 220KV circuit breaker is 252 kV, while its rated current is 4000 A. The rated, alarm, and locking air pressures are respectively 0.5, 0.45, and 0.43 MPa. 3. The rated voltage of the 110KV circuit breaker is (145 KV), the rated current is (3150A), and the rated, alarm, and locking air pressures are respectively (0.6, 0.52, 0.5) MPa. The rated voltage of the 10KV circuit breaker is (10KV), and its rated current is (1250A). 4. The main transformer at this site is equipped with German MR on-load tap changers, featuring a total of (17) taps; among these, (9a, 9c) are transition taps, while (9b) is the starting tap. 5. The voltage regulation operations of the on-load tap changer must be carried out strictly in accordance with the curve specified by the dispatching authority; the voltage should be kept at the optimal level whenever possible, and only (one) tap can be adjusted at a time. Under normal conditions, voltage regulation should be carried out using an (electric) mechanism; when the voltage does not meet the requirements, there should be a (certain time interval) between the two adjustments. During operation, it is necessary to pay attention to monitoring (voltage meter, ammeter, tap position) as well as (voltage changes), and to (record) them. 6. The gas protection of the on-load tap changer in operation should be set to the (trip) position; tap-changer operations are strictly prohibited during (overload) or (system short-circuit faults). 7. The main transformer cooling system consists of (26 sets of fans), (26 sets of blade fans), (four sets of submersible pumps), and the XKW-nj2 type radiator control box. 8. It enables the cooling system to be activated automatically when the operating transformer reaches a certain oil temperature at the top layer or when the load reaches the specified value. 9. When performing power-on or power-off operations on the main transformer, it is necessary to (close the 110Kv and 220Kv neutral point grounding switches) and (activate the corresponding zero-sequence protection). 10. The zero-sequence protection and gap protection of the 4/1# main transformer can be (activated simultaneously for a short period), but they must not be (deactivated simultaneously). 11. When the breaking capacity of the circuit breaker reaches its designed value, it should be (overhauled). 12. For the electrically operated isolating switch at my station, during normal operation, its control power switch should be (open); it should be (closed) before operation, and (open) immediately after operation. 13. Isolating switches should generally be operated from the control room. When remote electrical operation fails, electric or manual operation can be carried out on-site, but this must be permitted by the (station manager and technical supervisor) and can only be done in the presence of (on-site supervision). 14. Interlocks (electromagnetic or electromechanical) to prevent misoperation are installed between the isolating switch, grounding switch, and circuit breaker; switching operations must be carried out in sequence. If the interlock device fails or the isolating switch and grounding switch cannot be operated properly, it is necessary to strictly check the position status of the corresponding (circuit breaker and isolating switch) in accordance with the requirements of the interlock. Only after verification and with the permission of the station master or the responsible supervisor can the interlock be removed to carry out the operation. 15. For an isolating switch equipped with a grounding switch, the grounding switch must be closed only after the isolating switch is fully opened; conversely, the isolating switch can be closed only after the grounding switch is fully opened. The operation must be carried out thoroughly. 16. If a disconnector is pulled incorrectly while under load, and an arc is detected as soon as the blade begins to move away from the contact surface, it should be closed immediately. Once it has been opened, it must not be closed again to prevent (closing the switch under load), and the situation should be reported to superiors promptly. If the isolating switch is not closed properly or the three phases are out of phase, it should be (opened and reclosed). 17. The DC system serves as the power source for the substation’s protection, control, and signaling circuits. A serious failure in the DC system can disrupt the normal operation of the substation as a whole, causing severe disruptions in various circuits; therefore, it is very important to ensure that the DC system operates properly. 18. Although a single-point ground fault in the DC system does not immediately cause any adverse effects on the operation of the entire substation, it must be addressed promptly. If it develops into a two-point ground, it can cause serious hazards, potentially leading to (misoperation or failure to operate of the circuit breaker) and (blowing of the fuses in the control circuit). Since the DC system is related to the safe operation of the entire substation and power system, it should be reported to the dispatching department promptly. 19. For DC, a radial wiring scheme is adopted; each charger handles half of the load. Closing circuits at any point is prohibited during normal operation. When one charger or one set of batteries fails and stops operating, short-term parallel operation is allowed. 20. For less important DC loads and circuits that cannot be rerouted, use the (instant shutdown method) to check whether there is a ground fault in the circuit connected to that load ； For more important DC loads, use the (load transfer method) to check whether there is a ground fault in the circuit served by that branch. 1. Items for routine inspection of transformers. Check and record the operating temperature of the transformer as well as the ambient temperature; calculate the temperature rise. Examine the load and voltage levels, and check the indication of the maximum oil temperature. 2. Monitor to ensure that there are no abnormalities in the oil level in the oil conservator, and check whether the operating temperature exceeds the limits. 3. Check for any abnormal noises or vibrations in the equipment. 4. Ensure that there is no oil leakage. 5. Examine the color change of the silica gel, as well as the oil level and color in the oil seal cup to confirm they are normal. 6. Check the oil levels in the high, low, and neutral point bushings. 7. Verify that there is no oil leakage. 8. Inspect the porcelain tubes for any damage or discharge issues. 9. Check for dust contamination. 10. Ensure that the cooler is operating properly, and check for any oil leakage in the gas relay as well as for the presence of any gases inside. Also, check whether the neutral point is loose or overheating. 2. Principles for emergency shutdown of the transformer. 1. The noise emitted by the transformer increases significantly, which is abnormal; there are also sounds of explosions inside it. 2. Severe oil leakage or spraying occurs, causing the oil level to drop below the limit indicated by the oil gauge. 3. The bushings are severely damaged and exhibit discharge phenomena. 4. The transformer starts to smoke or catch fire. 5. In the event of a fault that threatens the safety of the transformer and the relevant protective devices or circuit breakers fail to function, the duty personnel should immediately shut down the transformer. 6. The transformer is operating without any protection. 7. When equipment nearby the transformer catches fire, explodes, or some other situation arises that poses a serious threat to the transformer, the duty personnel should immediately shut down the transformer. 8. If the increase in temperature is caused by a malfunction in the cooling system and it cannot be repaired while the transformer is still in operation, the transformer should be shut down for repairs. Under normal load and cooling conditions, if the transformer’s temperature rises abnormally and continues to increase, and it is confirmed through inspection that the temperature readings are accurate, it is considered that an internal fault has occurred in the transformer; in such cases, the transformer should be shut down urgently. 3. Reasons for the activation of the transformer’s backup protection. 1. The system frequency decreases or the system voltage is too high, causing the over-excitation protection to activate. 2. A line fault occurs; the circuit breaker for that line fails to operate or the protection system fails to function. 3. A busbar fault occurs; the busbar differential protection fails to operate. 4. A fault occurs within the range covered by the main protection of the main transformer, and the main protection fails to function. 5. Special inspection items for circuit breakers. 1. During strong winds, check the movement of the conductors to ensure there are no broken strands, and verify that there are no foreign objects stuck to the conductors or the top of the circuit breaker.
2. After heavy rain, check whether the foundation of the switch has sunk and whether there is any arcing in the bushings.
3. After heavy snowfall, monitor the melting of the snow; if a particular joint melts faster than others, it indicates that overheating has occurred there. If melted snow forms ice slides, it should be dealt with promptly.
4. On foggy days, check for any discharge or sparking in the bushings.
5. After hailstorms, inspect the porcelain insulators for any damage or cracks.
6. Under overload conditions, check whether the joints in the current-conducting parts are overheating and turning red.
7. After cutting off the fault current, check whether the circuit breaker itself is deformed and whether there are any abnormalities in the current-conducting parts.
5. Routine inspection items for isolating switches. 1. The supporting insulators of the isolator should be clean and in good condition, with no signs of discharge or abnormal noises.
2. The contacts of the isolator should make good contact; there should be no broken or loose screws, and no severe heating or deformation. The temperature of the isolator’s connections and leads should not exceed 70°C.
3. The mechanical parts of the isolator, such as its body, linkage rods, and shafts, should not be deformed. Pins should not have fallen out, and all connections should be secure with the parts in the correct positions.
4. The blades of the isolator should be fully closed and in good contact with each other.
5. The anti-misoperation locking devices of the isolator should be in good working order; the electromagnetic locks and mechanical locks should not be damaged.
6. The door of the isolator’s operating mechanism box should be tightly closed and properly sealed, and a dehumidifier should be in use.
7. There should be no debris on the live parts of the isolator.
8. Procedures for dealing with a tripped DC power supply switch. 1. Determine the affected area based on the location of the small switch. 2. Request to deactivate the protected devices that are affected. 3. Identify the cause of the fault; if the cause is unknown and no abnormalities are found, with the approval of the station manager and technicians, it may be possible to attempt to restart the small switch (step by step). 4. If restart is successful, request to restore the protection functions. 5. If the restart is unsuccessful, take necessary safety measures and take appropriate actions based on the current operating status of the protection system. 6. Report the defect for further handling. III. Essay questions: (20 points for question 1, 10 points for question 2, 10 points for question 3, totaling 40 points) 1. Causes of activation of the transformer’s heavy gas protection and differential protection, as well as procedures for dealing with such incidents. Reasons for the heavy gas protection to activate: 1. A fault occurred inside the transformer; 2. A fault in the secondary circuit of the protection device. Actions taken in response to the incident: 1. Reset the audible alarm, record the time, note the information displayed on the indicator panels, and report the incident details shown on the monitoring screen to the dispatch operator ； 2. Check the operation status of the protection devices, clear any flashing signals, and inspect whether the pressure relief valve and oil breather of the main transformer are leaking oil. Verify that the oil temperature and level are normal, and check whether there is gas inside the gas relay; report these findings to the dispatch team.
3. If there is oil leakage from the main transformer, or if the oil temperature is too high or the oil level is abnormal, it is strictly prohibited to restore power to the main transformer.
4. If the gas protection activates while someone is working on the secondary circuit, and after inspection no abnormalities are found in the main transformer, report to the dispatch team and follow their instructions.
5. If a DC ground fault or a problem exists in the secondary circuit at the same time as the gas protection activates, report the situation to the dispatch team and follow their instructions.
6. If there is gas inside the gas relay, collect the gas for analysis.
7. Power must not be restored until the cause of the heavy gas protection activation is identified.
Causes of differential protection activation:
1. Internal faults in the main transformer, resulting in the failure of the heavy gas protection to function.
2. Faults in the main transformer’s bushings.
3. Faults in the wiring between the main transformer and the circuit breaker’s CT.
4. Faults in the CT itself.
5. Faults in the secondary circuit.
6. Human error or accidental activation.
Handling procedures:
1. Activate the alarm signals, record the time, note any optical signals, and report the incident to the dispatch operator via the monitoring system.
2. Check the operation status of the protection devices, clear any flashing signals, and determine whether there are any faults within the range covered by the differential protection.
3. Check whether the oil temperature and level of the main transformer are normal.
4. Check for any obvious short-circuit faults in the main transformer and within the range covered by the differential protection.
5. Check for any abnormalities in the differential relay and the secondary circuit.
6. If no abnormalities are found during visual inspections, and it is confirmed that the differential protection activated due to a problem with the relay or the secondary circuit, report to the dispatch team. With their approval, disable the differential protection and attempt to restore power to the main transformer.
7. If the differential protection was activated due to a fault in the nearby area, isolate the fault first before attempting to restore power to the main transformer.
8. Power must not be restored until the cause of the fault is identified.
2. Causes of circuit breaker failure to open and procedures for handling such incidents. 1. Mechanical reasons: (1) Insufficient impact force from the opening electromagnet; (2) Failure of the opening spring; (3) Welding or mechanical jamming of the contacts, as well as faults in the transmission mechanism. 2. Electrical reasons: (1) Loose contacts in the opening circuit, improper operation of the auxiliary switch, or poor contact due to a blown control fuse; (2) Short circuits or broken wires in the opening coil; (3) The SF6 gas pressure dropping below the locking threshold; (4) Too low operating voltage or insufficient power supply capacity. Remedies: (1) Any faults identified during inspection should be corrected immediately. If no fault is found or it cannot be eliminated, the circuit breaker should be stopped immediately and the company informed. (2) When a circuit breaker trips during operation, the series substitution method should be used to take the tripped circuit breaker out of service, while keeping its mechanism in its original state. 3. Causes of overheating in isolating switches and methods for dealing with it. Reason: The isolating switch overheats during operation, mainly due to excessive load, poor contact between the contacts, or incomplete closing during operation. Solutions: 1. In a double-bus wiring configuration, if the isolating switch on one bus overheats, the circuit breaker can be switched to operate on the other bus through switching operations. 2. In a single-bus wiring configuration, if the isolating switch on one bus overheats and it is not possible to shut down that bus immediately, the load must be reduced and close monitoring should be carried out; efforts should be made to transfer the load so that the bus can be shut down. I hope this helps. This post was last edited by liss1543 on 2008-2-22 21:02.]
2. For dual- or triple-power-source transformers: 1) Under normal circumstances, during a power outage, the switch on the low-voltage side should be turned off first, then the one on the medium-voltage side, and finally the one on the high-voltage side; after that, the circuit breakers on each side should be opened. The sequence for restoring power is the reverse of this. 2) In special situations, the sequence for turning the transformer on or off also needs to take into account the configuration of protective devices and the distribution of electrical currents.
5. What are the basic principles of first aid? Active measures should be taken at the scene to save the lives of the injured, alleviate their injuries, and reduce their suffering; depending on the severity of their injuries, immediate contact should be made with emergency medical services for treatment. The hallmark of successful first aid is rapid action and correct procedures, as any delay or mistake can lead to worsening of the injured person’s condition or even death. III. Essay questions: (5 points per question, 10 points in total) 1. Briefly describe the procedure for performing electrical switch operations. 1. Issuing and accepting operation tasks 2. Filling out operation tickets 3. Reviewing operation tickets 4. Issuing and receiving commands for operation execution 5. Simulation operations 6. Actual operations 7. Inspecting the equipment 8. Reporting on the operations and stamping them as “completed” 9. Keeping relevant records. 2. Safety measures in substations during line work. The switching on and off of power to the line must be carried out in accordance with the instructions of the duty dispatcher or the person authorized to work on the line. In the event of a power outage, all circuit breakers, line isolators, and busbar isolators that could cause power to be supplied to the line must first be turned off. The pull-out switches should be moved to the testing or maintenance position. After confirming that there is no voltage present, ground wires should be installed at all points on the line where power might be supplied, or the grounding switches should be closed. Signs reading “Do not close – someone is working on the line” should be attached to the operation handles of both circuit breakers and isolators. Such signs should also be displayed on the screens at the locations where these devices are operated. According to the ‘On-site Operation Procedures’: 1. Fill in the blanks: 1) The model of the main transformer at this station is (SFPSZ10–150000/220); the connection type is (Yn,YN0,D11); the rated voltage is ((220 ±8×1.25 %)/121/10.5); the rated current is 393.6/715.7/4123.9; the rated capacity is 150000/150000/75000; the cooling method is ONAN/ONAF/OFAF. 2) The rated voltage of the 220KV circuit breaker is 252 kV, while its rated current is 4000 A. The rated, alarm, and locking air pressures are respectively 0.5, 0.45, and 0.43 MPa. 3. The rated voltage of the 110KV circuit breaker is (145 KV), the rated current is (3150A), and the rated, alarm, and locking air pressures are respectively (0.6, 0.52, 0.5) MPa. The rated voltage of the 10KV circuit breaker is (10KV), and its rated current is (1250A). 4. The main transformer at this site is equipped with German MR on-load tap changers, featuring a total of (17) taps; among these, (9a, 9c) are transition taps, while (9b) is the starting tap. 5. The voltage regulation operations of the on-load tap changer must be carried out strictly in accordance with the curve specified by the dispatching authority; the voltage should be kept at the optimal level whenever possible, and only (one) tap can be adjusted at a time. Under normal conditions, voltage regulation should be carried out using an (electric) mechanism; when the voltage does not meet the requirements, there should be a (certain time interval) between the two adjustments. During operation, it is necessary to pay attention to monitoring (voltage meter, ammeter, tap position) as well as (voltage changes), and to (record) them. 6. The gas protection of the on-load tap changer in operation should be set to the (trip) position; tap-changer operations are strictly prohibited during (overload) or (system short-circuit faults). 7. The main transformer cooling system consists of (26 sets of fans), (26 sets of blade fans), (four sets of submersible pumps), and the XKW-nj2 type radiator control box. 8. It enables the cooling system to be activated automatically when the operating transformer reaches a certain oil temperature at the top layer or when the load reaches the specified value. 9. When performing power-on or power-off operations on the main transformer, it is necessary to (close the 110Kv and 220Kv neutral point grounding switches) and (activate the corresponding zero-sequence protection). 10. The zero-sequence protection and gap protection of the 4/1# main transformer can be (activated simultaneously for a short period), but they must not be (deactivated simultaneously). 11. When the breaking capacity of the circuit breaker reaches its designed value, it should be (overhauled). 12. For the electrically operated isolating switch at my station, during normal operation, its control power switch should be (open); it should be (closed) before operation, and (open) immediately after operation. 13. Isolating switches should generally be operated from the control room. When remote electrical operation fails, electric or manual operation can be carried out on-site, but this must be permitted by the (station manager and technical supervisor) and can only be done in the presence of (on-site supervision). 14. Interlocks (electromagnetic or electromechanical) to prevent misoperation are installed between the isolating switch, grounding switch, and circuit breaker; switching operations must be carried out in sequence. If the interlock device fails or the isolating switch and grounding switch cannot be operated properly, it is necessary to strictly check the position status of the corresponding (circuit breaker and isolating switch) in accordance with the requirements of the interlock. Only after verification and with the permission of the station master or the responsible supervisor can the interlock be removed to carry out the operation. 15. For an isolating switch equipped with a grounding switch, the grounding switch must be closed only after the isolating switch is fully opened; conversely, the isolating switch can be closed only after the grounding switch is fully opened. The operation must be carried out thoroughly. 16. If a disconnector is pulled incorrectly while under load, and an arc is detected as soon as the blade begins to move away from the contact surface, it should be closed immediately. Once it has been opened, it must not be closed again to prevent (closing the switch under load), and the situation should be reported to superiors promptly. If the isolating switch is not closed properly or the three phases are out of phase, it should be (opened and reclosed). 17. The DC system serves as the power source for the substation’s protection, control, and signaling circuits. A serious failure in the DC system can disrupt the normal operation of the substation as a whole, causing severe disruptions in various circuits; therefore, it is very important to ensure that the DC system operates properly. 18. Although a single-point ground fault in the DC system does not immediately cause any adverse effects on the operation of the entire substation, it must be addressed promptly. If it develops into a two-point ground, it can cause serious hazards, potentially leading to (misoperation or failure to operate of the circuit breaker) and (blowing of the fuses in the control circuit). Since the DC system is related to the safe operation of the entire substation and power system, it should be reported to the dispatching department promptly. 19. For DC, a radial wiring scheme is adopted; each charger handles half of the load. Closing circuits at any point is prohibited during normal operation. When one charger or one set of batteries fails and stops operating, short-term parallel operation is allowed. 20. For less important DC loads and circuits that cannot be rerouted, use the (instant shutdown method) to check whether there is a ground fault in the circuit connected to that load ； For more important DC loads, use the (load transfer method) to check whether there is a ground fault in the circuit served by that branch. 1. Items for routine inspection of transformers. Check and record the operating temperature of the transformer as well as the ambient temperature; calculate the temperature rise. Examine the load and voltage levels, and check the indication of the maximum oil temperature. 2. Monitor to ensure that there are no abnormalities in the oil level in the oil conservator, and check whether the operating temperature exceeds the limits. 3. Check for any abnormal noises or vibrations in the equipment. 4. Ensure that there is no oil leakage. 5. Examine the color change of the silica gel, as well as the oil level and color in the oil seal cup to confirm they are normal. 6. Check the oil levels in the high, low, and neutral point bushings. 7. Verify that there is no oil leakage. 8. Inspect the porcelain tubes for any damage or discharge issues. 9. Check for dust contamination. 10. Ensure that the cooler is operating properly, and check for any oil leakage in the gas relay as well as for the presence of any gases inside. Also, check whether the neutral point is loose or overheating. 2. Principles for emergency shutdown of the transformer. 1. The noise emitted by the transformer increases significantly, which is abnormal; there are also sounds of explosions inside it. 2. Severe oil leakage or spraying occurs, causing the oil level to drop below the limit indicated by the oil gauge. 3. The bushings are severely damaged and exhibit discharge phenomena. 4. The transformer starts to smoke or catch fire. 5. In the event of a fault that threatens the safety of the transformer and the relevant protective devices or circuit breakers fail to function, the duty personnel should immediately shut down the transformer. 6. The transformer is operating without any protection. 7. When equipment nearby the transformer catches fire, explodes, or some other situation arises that poses a serious threat to the transformer, the duty personnel should immediately shut down the transformer. 8. If the increase in temperature is caused by a malfunction in the cooling system and it cannot be repaired while the transformer is still in operation, the transformer should be shut down for repairs. Under normal load and cooling conditions, if the transformer’s temperature rises abnormally and continues to increase, and it is confirmed through inspection that the temperature readings are accurate, it is considered that an internal fault has occurred in the transformer; in such cases, the transformer should be shut down urgently. 3. Reasons for the activation of the transformer’s backup protection. 1. The system frequency decreases or the system voltage is too high, causing the over-excitation protection to activate. 2. A line fault occurs; the circuit breaker for that line fails to operate or the protection system fails to function. 3. A busbar fault occurs; the busbar differential protection fails to operate. 4. A fault occurs within the range covered by the main protection of the main transformer, and the main protection fails to function. 5. Special inspection items for circuit breakers. 1. During strong winds, check the movement of the conductors to ensure there are no broken strands, and verify that there are no foreign objects stuck to the conductors or the top of the circuit breaker.
2. After heavy rain, check whether the foundation of the switch has sunk and whether there is any arcing in the bushings.
3. After heavy snowfall, monitor the melting of the snow; if a particular joint melts faster than others, it indicates that overheating has occurred there. If melted snow forms ice slides, it should be dealt with promptly.
4. On foggy days, check for any discharge or sparking in the bushings.
5. After hailstorms, inspect the porcelain insulators for any damage or cracks.
6. Under overload conditions, check whether the joints in the current-conducting parts are overheating and turning red.
7. After cutting off the fault current, check whether the circuit breaker itself is deformed and whether there are any abnormalities in the current-conducting parts.
5. Routine inspection items for isolating switches. 1. The supporting insulators of the isolator should be clean and in good condition, with no signs of discharge or abnormal noises.
2. The contacts of the isolator should make good contact; there should be no broken or loose screws, and no severe heating or deformation. The temperature of the isolator’s connections and leads should not exceed 70°C.
3. The mechanical parts of the isolator, such as its body, linkage rods, and shafts, should not be deformed. Pins should not have fallen out, and all connections should be secure with the parts in the correct positions.
4. The blades of the isolator should be fully closed and in good contact with each other.
5. The anti-misoperation locking devices of the isolator should be in good working order; the electromagnetic locks and mechanical locks should not be damaged.
6. The door of the isolator’s operating mechanism box should be tightly closed and properly sealed, and a dehumidifier should be in use.
7. There should be no debris on the live parts of the isolator.
8. Procedures for dealing with a tripped DC power supply switch. 1. Determine the affected area based on the location of the small switch. 2. Request to deactivate the protected devices that are affected. 3. Identify the cause of the fault; if the cause is unknown and no abnormalities are found, with the approval of the station manager and technicians, it may be possible to attempt to restart the small switch (step by step). 4. If restart is successful, request to restore the protection functions. 5. If the restart is unsuccessful, take necessary safety measures and take appropriate actions based on the current operating status of the protection system. 6. Report the defect for further handling. III. Essay questions: (20 points for question 1, 10 points for question 2, 10 points for question 3, totaling 40 points) 1. Causes of activation of the transformer’s heavy gas protection and differential protection, as well as procedures for dealing with such incidents. Reasons for the heavy gas protection to activate: 1. A fault occurred inside the transformer; 2. A fault in the secondary circuit of the protection device. Actions taken in response to the incident: 1. Reset the audible alarm, record the time, note the information displayed on the indicator panels, and report the incident details shown on the monitoring screen to the dispatch operator ； 2. Check the operation status of the protection devices, clear any flashing signals, and inspect whether the pressure relief valve and oil breather of the main transformer are leaking oil. Verify that the oil temperature and level are normal, and check whether there is gas inside the gas relay; report these findings to the dispatch team.
3. If there is oil leakage from the main transformer, or if the oil temperature is too high or the oil level is abnormal, it is strictly prohibited to restore power to the main transformer.
4. If the gas protection activates while someone is working on the secondary circuit, and after inspection no abnormalities are found in the main transformer, report to the dispatch team and follow their instructions.
5. If a DC ground fault or a problem exists in the secondary circuit at the same time as the gas protection activates, report the situation to the dispatch team and follow their instructions.
6. If there is gas inside the gas relay, collect the gas for analysis.
7. Power must not be restored until the cause of the heavy gas protection activation is identified.
Causes of differential protection activation:
1. Internal faults in the main transformer, resulting in the failure of the heavy gas protection to function.
2. Faults in the main transformer’s bushings.
3. Faults in the wiring between the main transformer and the circuit breaker’s CT.
4. Faults in the CT itself.
5. Faults in the secondary circuit.
6. Human error or accidental activation.
Handling procedures:
1. Activate the alarm signals, record the time, note any optical signals, and report the incident to the dispatch operator via the monitoring system.
2. Check the operation status of the protection devices, clear any flashing signals, and determine whether there are any faults within the range covered by the differential protection.
3. Check whether the oil temperature and level of the main transformer are normal.
4. Check for any obvious short-circuit faults in the main transformer and within the range covered by the differential protection.
5. Check for any abnormalities in the differential relay and the secondary circuit.
6. If no abnormalities are found during visual inspections, and it is confirmed that the differential protection activated due to a problem with the relay or the secondary circuit, report to the dispatch team. With their approval, disable the differential protection and attempt to restore power to the main transformer.
7. If the differential protection was activated due to a fault in the nearby area, isolate the fault first before attempting to restore power to the main transformer.
8. Power must not be restored until the cause of the fault is identified.
2. Causes of circuit breaker failure to open and procedures for handling such incidents. 1. Mechanical reasons: (1) Insufficient impact force from the opening electromagnet; (2) Failure of the opening spring; (3) Welding or mechanical jamming of the contacts, as well as faults in the transmission mechanism. 2. Electrical reasons: (1) Loose contacts in the opening circuit, improper operation of the auxiliary switch, or poor contact due to a blown control fuse; (2) Short circuits or broken wires in the opening coil; (3) The SF6 gas pressure dropping below the locking threshold; (4) Too low operating voltage or insufficient power supply capacity. Remedies: (1) Any faults identified during inspection should be corrected immediately. If no fault is found or it cannot be eliminated, the circuit breaker should be stopped immediately and the company informed. (2) When a circuit breaker trips during operation, the series substitution method should be used to take the tripped circuit breaker out of service, while keeping its mechanism in its original state. 3. Causes of overheating in isolating switches and methods for dealing with it. Reason: The isolating switch overheats during operation, mainly due to excessive load, poor contact between the contacts, or incomplete closing during operation. Solutions: 1. In a double-bus wiring configuration, if the isolating switch on one bus overheats, the circuit breaker can be switched to operate on the other bus through switching operations. 2. In a single-bus wiring configuration, if the isolating switch on one bus overheats and it is not possible to shut down that bus immediately, the load must be reduced and close monitoring should be carried out; efforts should be made to transfer the load so that the bus can be shut down. I hope this helps. This post was last edited by liss1543 on 2008-2-22 21:02.]
liss1543 took the time to find so many electrical engineering test questions and answers for me, which was of great help to me. :handshake I want to express my sincere gratitude to you! Your test questions focus on factory duty electricians (operational electricians); it would be better if there were more materials related to maintenance electricians as well.
You’re welcome; as fellow electrical engineers, let’s keep in touch more often in the future. As for the questions on electrical maintenance, I’ll look for them again. Since I work in substation operation and rectifier management, there is more information related to operation.
1. Why is a normally open contact that detects voltage on the line connected in series in the circuit of the normally closed contact of the synchronism relay in the three-phase reclosing start circuit? Answer: The purpose of connecting the KV normally open contact in series in the three-phase synchronism detection reclosing start circuit is to ensure that there is indeed voltage on the line before attempting synchronized reclosing. Additionally, under normal conditions, if for some reason the circuit operates in the voltage-free detection mode and the circuit breaker trips automatically, reclosing cannot take place because there is voltage on the line. In such cases, if the synchronism detection start circuit with the KV normally open contact is operated in parallel with the voltage-free detection start circuit, it is possible for the synchronism detection start circuit to correct this erroneous tripping. 2. What are the main differences between current transformers and reactance transformers, which are used in relay protection devices to convert current into voltage linearly? How does the former ensure that I1 and U2 are in phase? How does the latter achieve the desired phase relationship between I1 and U2? Answer: The main difference lies in the core structure; a current transformer has no air gap, while a reactance transformer has an air gap. The open-circuit excitation impedance is higher for a current transformer than for a reactance transformer ； In terms of the phase of the primary current and the secondary voltage, TA is in phase; the primary current of DKB lags behind the secondary voltage by 90° ； The secondary voltage of TA is taken from the voltage drop across the load resistor R; in order to achieve phase alignment for parallel operation, a variable resistor can be connected in parallel with the secondary coil at DKB, *with the resistance being adjusted to obtain the desired phase. 3. Why is it necessary to install single-point grounding and two-point grounding protection in the generator excitation circuit? Answer: Single-point grounding in the generator excitation circuit does not create a fault current path, and thus does not cause direct damage to the generator. However, the possibility of two-point grounding must be taken into account; therefore, a signal is generated by the single-point grounding protection to facilitate enhanced inspection and monitoring. When a two-point ground fault occurs in the generator excitation circuit: ① The generator rotor itself is damaged as a result of the considerable fault current flowing through the fault points ； ②It disrupts the symmetry of the air gap in the generator, causing severe vibration in the generator ； ③It causes the rotor to deform slowly, resulting in eccentricity and further exacerbating the vibrations. After one point is grounded, two-point grounding protection should be activated so that the machine can be shut down after a delay in the event of two-point grounding. 4. Why is a negative sequence voltage interlock device required for the generator’s loss of excitation protection? Answer: In cases of a single-phase or two-phase open circuit in the voltage transformer, as well as in situations of system asymmetry, the generator’s loss of excitation protection may need to be activated. To prevent the loss-of-excitation protection from operating erroneously under the above conditions, a negative-sequence voltage interlock device is installed; this ensures that the generator’s loss-of-excitation protection activates when there is actually a loss of excitation, while the negative-sequence voltage interlock relay does not activate. 5. For the protection scheme formed by the differential connections of the current transformers in phases A and C, what is the relative sensitivity of this scheme in the event of various inter-phase short-circuit faults occurring in the protected circuit, with a three-phase short circuit as the reference? Answer: In the case of a three-phase short circuit, the current flowing through the relay is Ik=√3I(3); whereas in the case of a short circuit between phases A and C, the current flowing through the relay is Ik=2I(2)=2×(√3/2•I(3)). During a BC two-phase short circuit, the current flowing through the relay is Ik = I(2) = I(3). When there is a short circuit between phases AB, the current flowing through the relay is Ik = I(2) = I(3). Therefore, with a sensitivity KS of 1 for three-phase short circuits as the reference, KS is 1 for an AC phase short circuit, and KS is 1/2 for AB and BC phase short circuits. 6. Why are busbar protection devices installed in high-voltage power grids? Answer: Although the probability of short-circuit failures occurring on the busbars is lower than that on transmission lines, the busbar serves as a point where multiple components converge. If such failures are not promptly addressed, they can lead to the escalation of the incident, even compromising the stability of the system and threatening the safe operation of the entire system, with very serious consequences. In a double-bus system, it is of great significance to be able to selectively and quickly isolate the faulty bus to ensure that the healthy bus can continue to operate. Therefore, busbar protection devices are required to be installed universally in high-voltage power grids. 7. What is a reactance transformer? Why does a reactance transformer have an air gap? Answer: A reactance transformer is a transformer whose primary winding is connected to a current source (i.e., the input power supply), while its secondary winding is in a nearly open-circuit state (i.e., it produces an output voltage). Its reactance value (referred to as the transfer impedance) is the excitation reactance. Since it is required that its excitation reactance Ze be small and it have good linear characteristics, a gap must be present in the magnetic circuit. The excitation impedance Ze of a reactive transformer is essentially reactive; therefore, U2 leads the primary current I1 by nearly 90°. 8. What are the conditions for synchronous paralleling? What effects will occur if these conditions are not met? Answer: The conditions for synchronous paralleling are that the voltage of the generator to be connected is equal to the system voltage, both have the same phase, and their frequencies are equal. When the above conditions are not met and parallel connection is used, inductive current will be generated. The greater the voltage difference, the larger the inrush current ； The greater the difference in frequency, the shorter the period of the inrush current. Inrush current is detrimental to both generators and power systems. 9. What is the maximum sensitivity angle of a direction impedance relay? Why is it necessary to set its maximum sensitivity angle equal to the impedance angle of the protected circuit? Answer: The impedance angle of the maximum operating impedance (amplitude) of a direction impedance relay is called its maximum sensitivity angle φs. When there is an interphase short circuit in the protected circuit, the angle between the short-circuit current and the voltage at the location where the relay is installed is equal to the impedance angle ΦL of the circuit. During a circuit short circuit, the impedance angle φm of the impedance measured by the direction impedance relay is equal to the impedance angle φL of the circuit. In order for the relay to operate in its most sensitive state, it is necessary to set the maximum sensitivity angle φS of the relay to this value. It is equal to the impedance angle φL of the protected circuit. 10. What is back-feeding of a voltage transformer? What impact does it have on protection devices? Answer: Charging a de-energized bus through the secondary side of a voltage transformer is called back-feeding. For example, in the case of a 220 kV voltage transformer with a turns ratio of 2200, even if the primary busbar is de-energized but not grounded, its impedance (including the busbar capacitance and insulation resistance) is relatively high; assuming it to be 1 MΩ, the impedance as seen on the secondary side of the voltage transformer is only 1,000,000 / (2200)² = 0.2 Ω, which is essentially a short circuit. As a result, the back-charge current is large (this current is primarily determined by the cable resistance and the leakage reactances of the two voltage transformers), causing the small switches on the secondary side of the voltage transformer to trip or the fuses to blow. This leads to a loss of voltage for the protective devices in operation, potentially resulting in incorrect or failed operation of those protective devices.
Notice on the Issuance of the \"**Power Grid Company Electricity Safety Work Procedures (Electrical Parts of Substations and Power Plants, Power Line Parts) (Trial Version)\” **Power Grid Safety Supervision [2005] No. 83 To all regional companies within the company’s system, provincial (autonomous region, municipality directly under the Central Government) power companies, and relevant directly affiliated units: In order to meet the requirements of advancements in grid production technology and changes in management systems, as well as to strengthen safety management at electricity production sites, **Power Grid Company has formulated the \"**Power Grid Company Electricity Safety Work Procedures (Electrical Parts of Substations and Power Plants, Power Line Parts) (Trial Version)\” based on the industry standards DL 408—1991 \"Electricity Industry Safety Work Procedures (Electrical Parts of Power Plants and Substations)\” and DL 409—1991 \"Electricity Industry Safety Work Procedures (Power Line Parts)\”. These procedures are now being issued and will be put into trial use within the company’s system starting from March 1, 2005. If any issues arise during the trial period, please inform the Safety Inspection Department of the **Power Grid Company promptly. Attachments: 1. “**Power Grid Company’s Rules for Electrical Safety Work (Electrical Parts of Substations and Power Plants)**” 2. “**Power Grid Company’s Rules for Electrical Safety Work (Power Line Parts)**” **Power Grid Company (Stamp)** February 17, 2005 1 General Provisions 1.1 These rules are formulated in accordance with relevant laws and regulations, taking into account the actual conditions of power production, in order to strengthen management at power production sites, regulate the behavior of various types of workers, and ensure the safety of personnel, power grids, and equipment. 1.2 Basic conditions at the work site 1.2.1 The production conditions and safety facilities at the work site shall meet the requirements of relevant standards and specifications, and the personal protective equipment provided to workers must be of qualified quality and available in sufficient quantity. 1.2.2 First-aid kits should be provided in places where people work regularly and on construction vehicles to store first-aid supplies, and a designated person should be assigned to regularly check, replenish, or replace them. 1.2.3 Safety tools used on site shall be qualified and meet relevant requirements. 1.2.4 All types of workers should be informed of the hazard factors present at their work sites and positions, as well as the preventive measures and emergency response procedures in case of accidents. 1.3 Basic requirements for workers 1.3.1 As determined by a physician, there should be no health conditions that prevent them from working (a physical examination is required at least once every two years). 1.3.2 Possess the necessary electrical knowledge and professional skills, be familiar with the relevant sections of these regulations based on the nature of the work, and pass the examination. 1.3.3 Possess the necessary knowledge of safe production, learn emergency first aid, and in particular, learn first aid for electric shock. 1.4 Education and Training 1.4.1 All types of workers shall receive appropriate safety production education and job-specific skill training, and must pass examinations before taking up their posts. 1.4.2 Operators shall be tested on these procedures once a year. Those who have interrupted electrical work for more than 3 months due to certain reasons must restudy these regulations and pass an examination before they can resume working. 1.4.3 New personnel working in electrical tasks, contract workers, and temporary workers (management staff, temporary laborers, etc.) must receive safety training before they can go to the work site to carry out assigned tasks, and they are not allowed to work alone. 1.4.4 Staff from external units who undertake electrical work on the company’s systems, or those who are involved in such work as outsiders, must be familiar with these regulations and pass relevant examinations before they can start working. Before starting work, the equipment operation and management unit should inform the site staff about the wiring of electrical equipment, potential hazards, and safety precautions. 1.5 Anyone who discovers a violation of these procedures must stop it immediately; operations can resume only after the violation has been corrected. All types of workers have the right to refuse orders that violate safety regulations or force them to carry out dangerous tasks ； In the event of an emergency that directly endangers the safety of people, power grids, and equipment, it is permissible to stop operations or evacuate the work site after taking possible emergency measures, and to report immediately. 1.6 While testing and introducing new technologies, new processes, new equipment, and new materials, corresponding safety measures should be established and implemented upon approval by the chief engineer of the unit. 1.7 Electrical equipment is divided into high-voltage and low-voltage types: High-voltage electrical equipment: those with a voltage relative to ground of 1000V or above ； Low-voltage electrical equipment: Those with a voltage to ground of 1000V or less. 1.8 These regulations apply to personnel working on electrical generation, transmission, transformation, distribution systems, as well as on user electrical equipment that is in use (including those involved in infrastructure installation and rural electricity work); other organizations and relevant personnel should refer to these regulations as well. Electrical equipment in use refers to all electrical equipment that is under voltage, some of which are under voltage, or those that become under voltage as soon as they are operated. Each unit may formulate supplementary provisions and implementation details for these regulations based on the actual conditions on site, and such provisions shall be put into effect upon approval by the unit’s production supervisor (chief engineer). 2 Basic requirements for the operation of high-voltage equipment 2.1 General safety requirements 2.1.1 Operators should be familiar with electrical equipment. Individual duty personnel or the person in charge of operational duty should also have practical work experience. 2.1.2 High-voltage equipment that meets the following conditions may be monitored or operated by a single person: 1) The isolation booth for indoor high-voltage equipment is equipped with a barrier that is at least 1.7 meters in height, is securely installed, and locked ； 2) Indoor high-voltage circuit breakers (switches) whose operating mechanisms are isolated from the circuit breaker (switch) by a wall or metal plate, or those equipped with remote operating mechanisms. 2.1.3 Whether the high-voltage equipment is energized or not, workers must not remove the barriers alone or cross them to carry out work ； If it is necessary to remove the barrier, a supervisor must be present, and the safety distance specified in Table 2-1 must be maintained. Table 2-1 Safe distance when the equipment is not powered off Voltage level (kV) 10 and below (13.8) 20, 35 63(66), 110 220 330 500 Safe distance (m) 0.70 1.00 1.50 3.00 4.00 5.00 Note: For voltage levels not listed in the table, the safe distance corresponding to the next higher voltage level shall be applied. 2.1.4 For the exposed parts of 10, 20, and 35 kV distribution installations that cross pedestrian walkways or work areas, if the height of the conductive parts above the ground is less than 2.7 m, 2.8 m, and 2.9 m respectively, protective grids must be installed on both sides and at the bottom of such exposed parts. 2.1.5 On the traffic passages in outdoor high-voltage distribution installations of 35 kV and above, height limit signs for vehicle safety shall be installed in accordance with Table 2-2. Table 2-2 Safe distance between the outer perimeter of the vehicle (including its load) and the live parts without barriers Voltage level (kV): 35, 63(66), 110, 220, 330, 500 Safe distance (m): 1.15, 1.40, 1.65 (1.75 note), 2.55, 3.25, 4.55 Note: The numbers in parentheses are applicable to systems with an ungrounded neutral point at 110 kV. 2.1.6 In areas where indoor busbars are segmented, where busbars intersect, and in locations where maintenance work may lead to accidental contact with live equipment during partial power outages, permanent isolation barriers (guard screens) with clear markings should be installed. 2.1.7 Standby bays (standby bays with busbar connection strips and leads already connected to the busbars) shall have names and numbers, and be included within the scope of dispatching control. The operation handles of its isolating switch (disconnector) and the access doors should be locked. 2.1.8 After the pull-out switch is drawn out, check whether the isolation baffle is securely closed. The spare holes for the outlet cables of enclosed switchgear, or the spare terminal holes of the busbars, should be sealed using specialized tools. 2.1.9 The neutral point of the neutral-point grounding system of high-voltage equipment in operation shall be regarded as a live part. 2.2 Inspection of high-voltage equipment 2.2.1 When personnel who have been authorized by the unit to inspect high-voltage equipment alone carry out such inspections, they shall not engage in any other tasks, nor shall they remove or step over the barriers. 2.2.2 During thunderstorm weather, when it is necessary to inspect outdoor high-voltage equipment, insulating boots must be worn, and one should not approach lightning arresters or lightning rods. 2.2.3 In the event of disasters such as fires, earthquakes, typhoons, floods, etc., if it is necessary to inspect the equipment, approval from the relevant supervisors of the equipment operation management unit must be obtained, and the inspectors should maintain communication with their dispatching department. 2.2.4 In the event of a ground fault in high-voltage equipment, one must not approach the fault site within 4 meters indoors, and within 8 meters outdoors. Persons entering the aforementioned area must wear insulating boots, and insulating gloves must be worn when touching the equipment’s enclosures and frames. 2.2.5 When inspecting the distribution equipment or entering and leaving the high-voltage room, make sure to close the doors behind you. 2.2.6 There should be at least 3 keys for the high-voltage room, which are to be kept by the operating staff and handed over during shift changes. One is intended for use in emergency situations, another is for use by operators; the rest can be lent to approved personnel who inspect high-voltage equipment and to the supervisors of approved maintenance and construction teams, provided that a registration and signature are made, and they must be returned after the inspection or work for that day is completed. 2.3 Switching Operations 2.3.1 Switching operations shall be carried out in accordance with the instructions of the duty dispatcher or the person in charge of operation, after the recipient repeats them to confirm accuracy. Instructions should be accurate and clear, using standard scheduling terminology as well as the dual names of the equipment, namely its name and number. The person giving the order and the person receiving it should first introduce their respective units and names. The entire process of giving the order (including the other party repeating the order) as well as the moment when the order is received must be recorded by both parties, who should also keep a written record of it. The operators (including supervisors) should understand the purpose of the operation and the sequence of operations. If there are any doubts about an instruction, it should be clarified with the issuer before proceeding with it. 2.3.2 Switching operations can be carried out through local operation, remote control operation, or programmed operation. Devices that are operated remotely or via programs must meet the relevant technical requirements. 2.3.3 Classification of switching operations: 2.3.3.1 Supervised operation: Two persons perform the same operation. During supervision operations, one of the persons who is more familiar with the equipment acts as the supervisor. Especially important and complex switching operations are carried out by skilled operators under the supervision of the shift supervisor. 2.3.3.2 Single-person operation: An operation performed by one person. 1) When operating a substation with a single operator on duty, the operator fills out the operation ticket based on the operation instructions conveyed by the person giving orders over the phone, and repeats them to confirm accuracy. 2) Equipment, projects, and operators that require single-person operation must be approved by the equipment operation management unit, and the personnel must pass specialized assessments. 2.3.3.3 Maintenance personnel operations: Operations carried out by maintenance personnel. 1) Maintenance personnel of the enterprise who have passed the examination organized by the equipment operation management unit and been approved may carry out supervised operations to switch electrical equipment of 220 kV and below from hot standby to maintenance mode or from maintenance mode to hot standby mode; the supervisor shall be a maintenance personnel or an equipment operation personnel from the same unit. 2) The procedures for giving and receiving commands, as well as the safety requirements for operations carried out by maintenance personnel, shall be approved by the chief engineer (technical supervisor) of the equipment operation management unit, and filed with the relevant departments and dispatching agencies. 2.3.4 Operation Ticket: 2.3.4.1 Switching operations are carried out by the operator using an operation ticket (see Appendix A). 2.3.4.2 The operation ticket shall be filled in item by item using a pen or ballpoint pen. The operation tickets generated by computer should be in the same format as those handwritten ； The operation ticket must be clear and neat, and shall not be altered arbitrarily. The operator and supervisor shall verify the filled-in operation items against the schematic diagram or wiring diagram and sign respectively, after which they shall be reviewed and signed by the person in charge of operation (or the work leader when carried out by maintenance personnel). Only one operation task can be filled in for each operation ticket. 2.3.4.3 The following items should be included in the operation ticket: 1) The equipment to be switched on or off [circuit breakers (switches), isolating switches (disconnectors), grounding switches, etc.], voltage testing, installation or removal of grounding wires, installation or removal of fuses in the control circuits or voltage transformer circuits, switching of protection circuits and automation devices, and verification that there is indeed no voltage present ； 2) After closing and opening the equipment [circuit breakers (switches), isolators (disconnector switches), grounding switches, etc.], check the position of the equipment ； 3) When performing power-on and power-off operations, before pulling or closing the isolating switch (knife switch) or pulling out or pushing in the drawer-type switch, check that the circuit breaker (switch) is indeed in the off position ； 4) Before and after performing load reversal or disconnection/parallel connection operations, check the operation of the relevant power sources and the load distribution ； 5) Before closing the switch to supply power again after equipment maintenance, check that the grounding switches within the power supply area have been opened and that the grounding wires have been removed. 2.3.4.4 The operation ticket shall include the dual names of the equipment. 2.3.5 Basic conditions for switching operations: 2.3.5.1 There must be a primary system simulation diagram that corresponds to the on-site primary equipment and the actual operating mode (including various electronic wiring diagrams). 2.3.5.2 Operating equipment shall have clear markings, including: name, number, opening/closing indication, rotation direction, switching position indication, and device phase color. 2.3.5.3 High-voltage electrical equipment shall be equipped with comprehensive anti-misoperation interlock devices. The anti-misoperation interlock device must not be deactivated arbitrarily; any discontinuation of its operation must be approved by the chief engineer of the unit ； When exiting the anti-lockout device for a short period of time, approval from the substation manager or the on-duty shift supervisor of the power plant is required, and it must be reactivated as soon as possible in accordance with the procedures. 2.3.5.4 There must be instructions formally issued by the on-duty dispatcher and the person in charge of operation (using standard operational terminology), and pre-approved operation tickets must be used. 2.3.5.5 Mechanical locks shall be installed in the following three situations: 1) The handles of isolating switches (cutsouts) and the door panels that are not equipped with anti-misoperation locking devices or whose locking devices have failed ； 2) The energized bay doors when the electrical equipment is in cold standby and the door locking mechanism is disabled ； 3) During equipment maintenance, the operation handles of the isolating switches (cutsouts) on the power supply side in the circuit, as well as the door of the mechanism box for electrically operated isolating switches (cutsouts). Each mechanical lock requires a key to open it, and the keys must be numbered and kept securely. 2.3.6 Basic requirements for switching operations: 2.3.6.1 The operation of turning off power should be carried out in the order of circuit breaker (switch) – load-side isolator (disconnector) – power-source side isolator (disconnector), while the operation of turning power on should be performed in the reverse order. It is strictly prohibited to open or close isolating switches (knife switches) under load. 2.3.6.2 Before starting the operation, a verification simulation rehearsal should be conducted on the simulation diagram (or microcomputer-based anti-misoperation device, microcomputer monitoring device); only after confirming there are no errors should the operation proceed. Before operating, the equipment name, number, and location should be verified first. During operation, the monitoring and repetition system must be strictly followed (even when operating alone, the steps should be read aloud), and it is advisable to record the entire process. During the operation, steps should be carried out in the order specified in the operation ticket. After completing each step, check to ensure everything is correct and mark it with a “√”; conduct a final review after all steps have been finished. 2.3.6.3 During supervised operation, the operator must not carry out any actions without the supervisor’s consent. 2.3.6.4 If doubts arise during the operation, it is necessary to stop the operation immediately and report to the person who gave the instructions. Operation can be carried out only after further approval from the person in charge. It is prohibited to modify operation tickets without authorization, and it is prohibited to disable locking devices at will. The unlocking tools (keys) shall be kept sealed, and all operators and maintenance personnel are strictly prohibited from using them without authorization. In case of special circumstances, the use of unlocking tools (keys) must be approved by the on-duty dispatcher, shift supervisor, or station master. Single-operator operation: Maintenance personnel are strictly prohibited from unlocking during switchgear operations. To unlock it, it is necessary to wait until additional operators arrive at the site and complete the approval procedures before proceeding. The unlocking tool (key) should be sealed up promptly after use. 2.3.6.5 Insulating gloves must be worn when operating isolating switches (blade switches) with an insulating rod, or when operating circuit breakers (switches) and isolating switches (blade switches) through a transmission mechanism. When operating outdoor high-voltage equipment in rainy weather, the insulating rod should be equipped with a rain cover, and insulating boots should also be worn. If the resistance of the grounding grid does not meet the requirements, insulated boots should be worn even on sunny days. During thunderstorms, switching operations are generally not carried out, and it is prohibited to perform such operations on site. 2.3.6.6 When installing or removing high-voltage fuses, safety goggles and insulating gloves must be worn; insulating pliers should be used if necessary, and one must stand on an insulating mat or platform. 2.3.6.7 The breaking capacity of the circuit breaker (switch) shall meet the requirements of the power grid. If the blocking capacity is insufficient, the operating mechanism should be separated from the circuit breaker (switch) by a wall or metal plate; remote operation should be used, and the reclosing device should be disabled. 2.3.6.8 After the power is cut off to electrical equipment (including in the event of an accident), it is prohibited to touch the equipment or enter the enclosure before the relevant disconnect switches are opened and safety measures are taken, in order to prevent a sudden power restoration. 2.3.6.9 Climbing heights or poles is not permitted when operating alone. 2.3.6.10 The verification of the position of electrical equipment after operation shall be based on the actual position of the equipment. When the actual position cannot be seen, it can be determined by the mechanical position indicators, electrical indicators, instruments, as well as changes in various telemetry and telesignaling signals; at least two or more such indicators must show corresponding changes simultaneously in order to confirm that the equipment has been moved to its intended position. 2.3.6.11 In the event of an electric shock accident, in order to rescue the person affected, the power supply to the relevant equipment can be disconnected without permission; however, the incident must be reported to the dispatching office and higher-level authorities immediately afterward. 2.3.7 The following tasks do not require an operation ticket: 1) Emergency handling of accidents ； 2) Single operation of closing and opening the circuit breaker (switch) ； 3) Open or remove the only set of grounding switches or grounding wires in the entire station (plant). After completing the above operations, records should be kept, and the original records must be preserved for emergency accident handling. 2.3.8 Operation tickets for the same substation should be numbered sequentially in advance; operation tickets generated by computer should also be numbered sequentially before they are officially issued. Operation tickets are used in order of number. Cancelled operation tickets should be marked with the word “Cancelled”; those that have not been carried out should be marked as “Not executed”, and those that have been carried out should be marked as “Executed”. Operation tickets should be kept for one year. 2.4 Working on High-Voltage Equipment 2.4.1 Working on high-voltage equipment that is in use can be divided into three categories: 2.4.1.1 Work requiring a complete power shutdown refers to a situation where all high-voltage equipment indoors is powered off (including overhead lines and cable connections), and all doors leading to adjacent high-voltage rooms are locked; it also includes a complete power shutdown of outdoor high-voltage equipment (including overhead lines and cable connections). 2.4.1.2 Work involving partial power outage refers to a partial power outage of high-voltage equipment, or a situation where although all power is cut off inside a room, the doors leading to adjacent high-voltage rooms are not fully locked. 2.4.1.3 Work without power interruption refers to: 1) the work itself does not require a power outage and there is no risk of accidental contact with live parts ； 2) Permits work to be carried out on the enclosure of live equipment or its conductive parts. 2.4.2 Working on high-voltage equipment shall be carried out by at least two persons, and organizational and technical measures to ensure safety shall be implemented. 3 Organizational measures to ensure safety 3.1 Organizational measures for safe work on electrical equipment 3.1.1 Work order system ； 3.1.2 Work Permit System ； 3.1.3 Work supervision system ； 3.1.4 System of work interruptions, transfers, and termination. 3.2 Work Order System 3.2.1 For work on electrical equipment, a work order or an emergency repair form must be filled out; there are 6 methods for doing this: 1) Fill out the first type of work order for substations (power plants) (see Appendix B). 2) Fill out the first type of work order for power cables (see Appendix C). 3) Fill out the second type of work order for substations (power plants) (see Appendix D). 4) Fill out the second type of work order for power cables (see Appendix E). 5) Fill out the live working permit for substations (power plants) (see Appendix F). 6) Fill out the Substation (Power Plant) Accident Emergency Repair Form (see Appendix G). 3.2.2 Tasks that require the use of the first type of work order are: 1) Work on high-voltage equipment that necessitates a complete or partial power outage. 2) Work on secondary systems and circuits such as lighting requires shutting down high-voltage equipment or taking safety measures. 3) Work on high-voltage power cables that requires power interruption. 4) Other tasks that require shutting down high-voltage equipment or taking safety measures. 3.2.3 Tasks that require the use of the second type of work order include: 1) Work on control panels, low-voltage distribution panels, distribution boxes, and power main lines. 2) Work on secondary systems and circuits such as lighting does not require shutting down high-voltage equipment or taking safety measures. 3) Work on the excitation circuit of a rotating generator or synchronous condenser, or on the rotor resistance circuit of a high-voltage motor. 4) Non-operating personnel use insulating rods and voltage transformers to determine phase alignment, or use clamp ammeters to measure the current in high-voltage circuits. 5) Work on related locations and the enclosures of live equipment at distances greater than those specified in Table 2-1, as well as work where it is not possible to come into contact with the conductive parts of the live equipment. 6) Work on high-voltage power cables that does not require power outage. 3.2.4 Tasks that require the use of a live work permit are those involving live work or work carried out at a distance from adjacent live equipment that is less than the value specified in Table 2-1. 3.2.5 The task of filling out the accident emergency repair form is as follows: An accident emergency repair can be carried out without a work order, but an accident emergency repair form must be used. 3.2.6 Filling out and issuing work orders: 3.2.6.1 Work orders shall be filled out and issued using a pen or ballpoint pen, in two copies; the content must be accurate and clear, and no alterations shall be made arbitrarily. If there are any individual errors or missing words that need to be corrected, standard symbols should be used, and the handwriting must be clear. 3.2.6.2 Work orders generated or printed by computer shall use a uniform format; they must be reviewed by the work order issuer for accuracy before they can be executed, either by hand or via electronic signature. One copy of the work order should be kept at the work site and held by the person in charge of the work ； Another copy is held by the work permit issuer and handed over accordingly. The work permit issuer shall record the work order number, work task, permission time, and completion time in the register. 3.2.6.3 In one work order, the work order issuer, the person in charge of the work, and the work permit issuer shall not hold these roles simultaneously. The person in charge of the work can fill out the work order. 3.2.6.4 Work orders shall be issued by the equipment operation and management unit, or they may also be issued by the maintenance, testing, and infrastructure construction units after being reviewed and approved by the equipment operation and management unit. The list of work order issuers and work supervisors from the maintenance, testing, and infrastructure units shall be submitted in advance to the relevant equipment operation and management unit for record-keeping. For the first type of work order, a master work order and separate work orders may be used when the work order issuer deems it necessary, with both being issued simultaneously. The relevant regulations regarding the filling out and authorization of general work orders and separate work orders shall be implemented after approval by the leader in charge of production at the unit (the chief engineer). 3.2.6.5 When the power supply unit or the construction unit carries out work inside the user’s substation, the work order shall be issued by the power supply unit, the construction unit, or the user’s unit that has the authority to issue such work orders. 3.2.7 Use of work orders: 3.2.7.1 Only one work order can be issued to a single work supervisor, and the location of work specified on the work order is limited to one electrical connection point. If the construction equipment is of the same voltage, located on the same floor, and power is turned off and on simultaneously without coming into contact with live conductors, then it is permitted to use one work order for several electrical connection points. All safety measures specified in the work order must be implemented at once before starting work. 3.2.7.2 If an electrical connection point or a distribution device loses power entirely, work at all different locations can be covered by one work order, provided that the main tasks to be carried out are specified in detail. When several teams are working simultaneously, a work order can be issued to a single overall supervisor; in the section for team members, only the supervisors of each team need to be listed, without the need to include the names of all team members. If, by the scheduled time, some of the work has not been completed and it is necessary to continue working without interfering with the power supply process, a new work order must be issued in accordance with the conditions under which the equipment on site will be under voltage after power is supplied. Only after safety measures have been put in place can work proceed. 3.2.7.3 For performing the same type of work without power interruption sequentially at several electrical connection points, one second type of work order can be used. 3.2.7.4 For consecutive live work of the same type carried out within the same substation or power plant step-up station, one live work permit may be used. 3.2.7.5 When entering a substation or a step-up station in a power plant with a work order for working on overhead lines or cables, an additional copy of the work order must be prepared; the person in charge of the work shall submit one of these copies to the person authorized to grant work permits at the substation or power plant in order to obtain permission to carry out the work. The list of work order issuers and work supervisors from the aforementioned units shall be submitted in advance to the relevant operation units for record-keeping. 3.2.7.6 When it is necessary to change team members, approval from the work supervisor must be obtained, and work may proceed only after providing safety instructions to the new staff members. The person in charge of the work shall not be changed unless under special circumstances. If a change is indeed necessary, it must be approved by the person who issued the work order, who shall also inform the person who granted the work permit; the person who granted the permit will then record the change in the work order. The person in charge of the work allows one change. The former and current task supervisors should hand over the tasks and safety measures. 3.2.7.7 When adding work tasks within the power outage area specified in the original work order, the person in charge of the work must obtain the consent of the work order issuer and the work permit issuer, and add the new work items to the work order. If it is necessary to modify or add safety measures, a new work order must be filled out, and the work permit procedure must be repeated. 3.2.7.8 If the person in charge of the work is changed or additional tasks are added, and the work order issuer is unable to handle it in person, contact should be made by phone, and this should be noted in the work order register and on the work order itself. 3.2.7.9 The first type of work order shall be delivered to the operating staff one day prior to the work; it can be delivered directly or via fax or local area network, but the approval for the work order sent by fax shall be granted only after the official work order arrives. Temporary work can be handed directly to the work permit issuer before work begins. The second type of work order and the live work order can be submitted to the work permit issuer in advance on the day the work is to be carried out. 3.2.7.10 If a work order is damaged and can no longer be used, a new work order must be filled out. 3.2.8 Validity period and extension of work permits: 3.2.8.1 The valid period for the first and second types of work permits, as well as those for live working, is limited to the approved maintenance period. 3.2.8.2 For the first and second types of work orders, extension procedures must be carried out. The person in charge of the work must submit an application to the person on duty for operation before the deadline for completion of the work (for maintenance equipment that falls under the jurisdiction and approval of the dispatch team, approval from the on-duty dispatcher is also required), and it is the person on duty for operation who will inform the person authorized to grant work permits to proceed with the procedures. The first and second types of work orders can only be extended once. 3.2.9 Basic requirements for the personnel listed on the work order: The issuer of the work order should be a production supervisor, technical specialist who is familiar with the technical capabilities of the personnel, aware of the condition of the equipment, knowledgeable about these regulations, and possesses relevant work experience; or it may be a person approved by the unit’s supervisor in charge of production. The list of work order issuers shall be published in writing. The person in charge of the work should be someone with relevant work experience, familiar with the equipment, aware of the capabilities of the team members, and knowledgeable about these procedures; such a person must also receive written approval from the production management of the work area (station or company). The work permit issuer should be an operator with relevant work experience, as approved in writing by the production management of the work area (station or company), or an operator from an approved maintenance unit (the person who carries out the work tasks and implements safety measures) ； The person authorized to issue work permits for user substations and distribution stations should be a high-voltage electrician holding a valid certificate. The dedicated supervisor should be a person with relevant work experience, familiar with the equipment and these procedures. 3.2.10 Safety responsibilities of the personnel listed on the work order: 3.2.10.1 Person issuing the work order: 1) Necessity and safety of the work ； 2) Are the safety measures specified on the work order correct and complete? ； 3) Whether the assigned work supervisor and team members are appropriate and sufficient. 3.2.10.2 Person in charge of work (supervisor): 1) Organize the work correctly and safely ； 2) Responsible for checking whether the safety measures listed in the work order are correct and complete, and whether the safety measures taken by the work permit issuer suit the actual conditions on site; additional measures shall be taken if necessary ； 3) Before starting work, inform the team members of the potential hazards, explain the safety and technical measures, and ensure that every team member is aware of them ； 4) Strictly implement the safety measures specified in the work order ； 5) Supervise and monitor team members to comply with these procedures, use personal protective equipment properly, and implement on-site safety measures ； 6) Whether the members of the work team are in good mental condition and whether any changes are appropriate. 3.2.10.3 Work Permit Issuer: 1) Responsible for verifying whether the safety measures specified in the work permit are correct and complete, as well as whether they suit the conditions at the site ； 2) Are the safety measures in place at the work site adequate? Supplement them if necessary ； 3) Responsible for checking whether the maintenance equipment poses a risk of sudden power restoration ； 4) Even if there is the slightest doubt regarding the contents listed in the work order, it should be clarified with the person who issued the work order; if necessary, detailed supplements should be requested. 3.2.10.4 Designated guardian: 1) Specify the person under guardianship and the scope of guardianship ； 2) Before starting work, explain the safety measures to the person under supervision, and inform them of the potential hazards and safety precautions ； 3) Supervise the persons under supervision to comply with these procedures and on-site safety measures, and promptly correct unsafe behaviors. 3.2.10.5 Team members: 1) Be familiar with the work content and procedures, understand the safety measures, identify potential hazards in the work, and carry out confirmation procedures ； 2) Strictly abide by safety regulations, technical procedures, and labor discipline, take responsibility for one’s own actions at work, show concern for each other’s work safety, and supervise the implementation of these procedures as well as on-site safety measures ； 3) Use safety tools and personal protective equipment correctly. 3.3 Work Permit System 3.3.1 After implementing the safety measures at the construction site, the work permit issuer must also complete the following procedures before the work team can begin working: 3.3.1.1 Together with the person in charge of the work, recheck the safety measures that have been put in place, specify the actual isolation measures for each piece of equipment, and confirm that the equipment to be repaired is indeed free of voltage. 3.3.1.2 Indicate to the person in charge of the work the location of the live equipment and the precautions to be taken during the work process. 3.3.1.3 The person in charge of the work and the work supervisor shall confirm and sign on the work order respectively. 3.3.2 Operators shall not change the operating wiring configuration of the equipment under maintenance. Neither the person in charge of the work nor the person who has issued the work permit shall change the safety measures without authorization. If it is necessary to make changes due to special circumstances during the work, consent from the other party must be obtained first. Any changes are promptly recorded in the duty log. 3.4 Work Supervision System 3.4.1 After the work permit procedures are completed, the work supervisor and the designated safety supervisor shall explain to the team members the tasks to be carried out, the division of responsibilities among the team members, the live parts involved, as well as the safety measures in place at the site. They must also inform the team members about the potential hazards, and confirmation procedures must be carried out before the team can begin working. The person in charge of the work and the designated supervisor should always be present at the work site, carefully overseeing the safety of the workers and promptly correcting any unsafe behaviors. 3.4.2 All staff members (including those in charge of the work) are not allowed to enter or remain alone inside the high-voltage room or in the area surrounding the high-voltage equipment. If required by the work (such as measuring polarity, conducting circuit continuity tests, etc.) and if the on-site equipment permits it, one or several persons with practical experience in the work team may be allowed to work in that room simultaneously, but the person in charge of the work must provide detailed instructions regarding safety precautions in advance. 3.4.3 The person in charge of the work may participate in the work team’s activities during a complete power outage. During partial power outages, work can only be carried out when safety measures are reliable and personnel are gathered in one work area to avoid accidentally touching live parts. The work order issuer or work supervisor shall, based on specific circumstances such as the safety conditions at the site, the scope of construction, and the requirements of the work, assign dedicated supervisors and determine the personnel to be supervised. A dedicated guardian shall not hold any other positions. When the designated guardian is temporarily away, the person under guardianship should be instructed to stop working or leave the work site, and work can resume only after the designated guardian returns. 3.4.4 During working hours, if the person in charge of the work has to leave the work site temporarily for some reason, they should assign a competent person to take over temporarily. Before leaving, they must give clear instructions regarding the work site and inform the team members. When the original person in charge returns to the work site, they should also follow the same handover procedures. If the person in charge of the work needs to be away from the work site for an extended period, the original work order issuer shall assign a new person in charge, complete the necessary change procedures, and inform all workers as well as the work permit issuer. The current and former person in charge of the work should carry out the necessary handover. 3.5 Systems for Work Interruptions, Transfers, and Completion 3.5.1 During a work interruption, the crew members should withdraw from the work site; all safety measures shall remain in place, and the work order shall continue to be held by the person in charge of the work. To resume work after the interruption, no approval from the work permit issuer is required. At the end of each day, the work area should be cleaned, any closed passages reopened, and the work order returned to the operators. When resuming work the next day, permission from the work permit issuer must be obtained, and the work ticket should be retrieved. The person in charge of the work must carefully recheck whether the safety measures meet the requirements specified in the work ticket, and a site meeting must be held before work can proceed. Without the supervision of a work supervisor or designated guardian, staff shall not enter the work site. 3.5.2 No one is allowed to restore power to the de-energized equipment until the work ticket completion procedures have been carried out. During breaks in work, if there is an emergency, the operators may close the circuit and supply power without returning the work order, but they must first inform the person in charge of the work. Action may only be taken after receiving confirmation that all members of the work team have left the work site and it is safe to do so. The following measures must also be taken: 1) Remove the temporary barriers, grounding wires, and warning signs, restore the permanent barriers, and replace them with signs that read “Stop, high voltage – danger!” ”signage ； 2) Personnel should be stationed at all roads to inform the work crew that \"the equipment has been powered on and work must cease.\" These personnel must not leave their posts until the work order is returned. 3.5.3 Before the maintenance work is completed, if it is necessary to apply a test operating voltage to the equipment, this must be done under the following conditions: 1) All personnel must evacuate the work area ； 2) Retire all work orders for this system, remove temporary barriers, grounding wires, and signboards, and restore the permanent barriers ； 3) The pressure testing shall be carried out by the operating personnel after a comprehensive inspection by the work supervisor and the operating staff confirms that everything is in order. If the work team needs to continue working, it must go through the work permit procedure again. 3.5.4 When working at several locations sequentially within the same electrical connection area using the same work order, all safety measures shall be implemented by the operators once before starting work, and no additional transfer procedures are required. However, when the person in charge of the work transfers the work location, they should inform the workers about the live areas, safety measures, and precautions. 3.5.5 After all work is completed, the work team shall clean and tidy up the site. The person in charge of the work should first conduct a thorough inspection. After all staff have left the work site, they should inform the operators about the items that were repaired, the problems identified, the test results, and any existing issues. Together with the operators, they should check the condition and status of the equipment, ensure that there are no items left behind, and verify that everything is clean. Finally, the completion time of the work should be recorded on the work order. Once signed by both parties, it indicates that the work is completed. The temporary barriers on the work order are removed, the signs are taken down, the permanent barriers are reinstalled, and any unremoved grounding wires or grounding switches are reported to the dispatch team; only then is the work order considered complete. 3.5.6 Power can be restored by closing the switch only after all work orders in the same power outage system have been completed, and upon permission from the on-duty dispatcher or the person in charge of operation. 3.5.7 Completed work orders and emergency repair forms for accidents shall be retained for one year. 4 Technical measures to ensure safety 4.1 Technical measures for safe work on electrical equipment 4.1.1 Power shutdown ； 4.1.2 Voltage testing ； 4.1.3 Grounding ； 4.1.4 Hang signboards and install barriers (fences). The above measures are carried out by operators or personnel authorized to perform the operations. 4.2 Power Outages 4.2.1 At the work site, the equipment that requires a power outage is as follows: 4.2.1.1 Equipment under maintenance ； 4.2.1.2 Equipment whose distance from the staff within their normal range of activity during work is less than that specified in the table ； Table 4-1 Normal operating range of personnel and safe distance from live equipment Voltage class (kV) 10 and below (13.8) 20, 35 63(66), 110 220 330 500 Safe distance (m) 0.35 0.60 1.50 3.00 4.00 5.00 Note: For voltage levels not listed in Table 4-1, the safe distance corresponding to the next higher voltage class shall be applied. 4.2.1.3 Equipment at 35 kV and below for which the safety distance is greater than that specified in Table 4-1 but less than that specified in Table 2-1, and which lacks insulation barriers or safety fences ； 4.2.1.4 Equipment in which the live parts are located behind, on either side of, or above and below the workers, with no reliable safety measures in place ； 4.2.1.5 Other equipment that requires power shutdown. 4.2.2 When performing maintenance on equipment that is powered off, all power supplies must be completely disconnected (the neutral point of any star-connected equipment that is in use should be considered live equipment). Working on equipment whose power supply is disconnected only by a circuit breaker (switch) is prohibited. The isolating switch (knife switch) should be opened, and the drawer switch should be moved to the testing or maintenance position; there must be a clear break point in all connections (except for some equipment where no clear break point can be observed). For transformers and voltage transformers associated with the equipment that is shut down, the connections on all sides of the equipment should be disconnected to prevent power from being fed back into the equipment that is under maintenance. 4.2.3 The control power and closing power supply for the maintenance equipment and the circuit breakers (switches) and isolators (disconnector switches) on the side where power may be supplied should be disconnected, and the operation handles of the isolators (disconnector switches) should be locked to prevent accidental power supply. 4.2.4 For maintenance equipment that is difficult to completely disconnect from the power supply, the electrical connection between the equipment and the power supply can be removed. 4.3 Voltage Testing 4.3.1 When performing voltage testing, a contact-type voltage tester suitable for the corresponding voltage level and that is of qualified quality should be used, and each phase should be tested separately at the points where grounding wires are installed or grounding switches are closed. Before testing for electricity, a test should first be conducted on a device that is powered on, to confirm that the voltage tester is in good working condition ； When it is not possible to conduct tests on devices powered by electricity, a high-voltage generator or similar can be used to verify that the voltage detector is in good condition. If testing for electricity on wooden poles, ladders, or frames and the device does not give a reading without a ground wire, a ground wire can be connected to the end of the insulating rod of the voltage detector, but this must be done with the permission of the person in charge of operations or the person in charge of the work. 4.3.2 Insulating gloves should be worn when performing high-voltage voltage testing. The length of the telescopic insulating rod of the voltage tester should be fully extended; when testing for voltage, the hand should hold the handle without going beyond the protective ring, and a safe distance should be maintained between the person and the voltage testing equipment. Direct outdoor voltage testing shall not be carried out in rainy or snowy weather. 4.3.3 For equipment that cannot be tested for electricity directly, indirect testing can be carried out. That is, check the changes in the mechanical indication position of the isolating switch (cutter), the electrical indications, as well as the readings of the instruments and live display devices; at least two or more of these indications should show corresponding changes simultaneously ； If remote operation is performed, the status indication of the isolating switch (disconnector), telemetry and telesignaling signals, as well as the indications from the live display device, should be checked simultaneously to conduct indirect voltage testing. For electrical equipment of 330 kV and above, indirect voltage testing methods can be used for voltage verification. 4.3.4 Signals indicating that the equipment is disconnected and that entry to the compartment is permitted, as well as permanently connected voltmeters, etc. – if they indicate power presence, work on the equipment is prohibited. 4.4 Grounding 4.4.1 The installation of grounding wires should be carried out by two persons (except for those projects where single-person installation is permitted with approval, as well as by operating personnel). 4.4.2 Once it is confirmed that the equipment has no voltage, the equipment under maintenance should be grounded immediately and its three phases short-circuited. Before grounding the cables and capacitors, they must be fully discharged phase by phase. The neutral point of capacitors connected in a star configuration should be grounded. Series-connected capacitors, as well as those that are disconnected from the rest of the capacitor bank, must be discharged individually. The casings of capacitors mounted on insulating supports also need to be discharged. 4.4.3 Ground wires shall be installed or grounding switches shall be closed at all points from which power may be supplied to the de-energized equipment; it shall be ensured that the ground wires in place maintain the required safety distance even when they move. 4.4.4 When induced voltage may be generated in the equipment under maintenance due to parallel or adjacent live equipment, grounding wires should be installed, or the workers should use personal protective grounding wires. The installed grounding wires must be recorded in the work order, while personal protective grounding wires are to be installed and removed by the workers themselves. 4.4.5 When performing maintenance work on the line side of a gantry structure, if the distance between the work location and the installed grounding wire is less than 10 m, it is not necessary to install an additional grounding wire even though the work location is outside the grounding wire. 4.4.6 If the maintenance section is divided into several electrically disconnected parts [such as sectional busbars separated into several sections by isolating switches or circuit breakers], each section shall be tested for electricity, grounded, and short-circuited separately. When the entire step-down substation loses power, the sections that may receive power again should be grounded and short-circuited, while it is not necessary to install grounding wires or close the grounding switches for every other section. 4.4.7 No circuit breaker (switch) or fuse shall be connected between the grounding wire, grounding switch, and the equipment under maintenance. If, due to equipment reasons, a circuit breaker (switch) is connected between the grounding switch and the equipment under maintenance, measures must be in place to ensure that the circuit breaker (switch) does not open after the grounding switch and the circuit breaker (switch) are closed. 4.4.8 On the distribution apparatus, the grounding wires shall be installed at the designated locations on the conductive parts of the apparatus; the paint at these locations shall be removed and black markings shall be applied. At appropriate locations on all power distribution devices, grounding terminals connected to the grounding grid shall be provided, and the grounding resistance shall meet the specified requirements. The grounding wire should be of the three-phase short-circuit type; if a phase-separated grounding wire is used, a combined grounding terminal for the three phases should be provided. 4.4.9 When installing a grounding wire, the grounding terminal should be connected first, followed by the conductor terminal; the grounding wire must make good contact, and the connection should be reliable. The sequence for removing the ground wire is the opposite. Insulated rods and insulated gloves must be used when installing or removing ground wires. The human body must not touch the ground wire or ungrounded wires to prevent electric shock from induced electricity. 4.4.10 The complete set of grounding wires shall be composed of multi-strand soft copper wires with transparent sheaths, whose cross-sectional area shall not be less than 25, and they shall also meet the requirements regarding short-circuit current at the installation location. The use of other wires as grounding wires or short circuits is prohibited. The ground wire should be fixed to the conductor using specialized clamps; it is strictly prohibited to use winding methods for grounding or short-circuiting. 4.4.11 Staff are strictly prohibited from moving or removing the grounding wire without authorization. Work on high-voltage circuits can only be carried out after all or part of the grounding wires are removed, such as when measuring the insulation resistance of busbars and cables, measuring circuit parameters, or checking whether the contacts of circuit breakers (switches) make simultaneous contact; for example: 1) Remove the grounding wire for one phase ； 2) Remove the ground wire and retain the short circuit wire ； 3) Remove all grounding wires or disconnect the grounding switch. The above work may be carried out only with the permission of the operating personnel (for grounding wires installed according to the dispatcher’s instructions, permission from the dispatcher is required). Resume immediately after the work is completed. 4.4.12 Each set of grounding wires shall be numbered and stored in a designated location. The storage location should also be numbered, and the grounding wire number should match the storage location number. 4.4.13 Records should be kept for the installation and removal of grounding wires, and clear instructions should be provided during shift handovers. 4.5 Hanging Signage and Installing Barriers (Fences) 4.5.1 On the operating handles of circuit breakers (switches) and isolators (disconnectors) that can supply power to the work area as soon as they are closed, signs stating “Do not close – people are working!” must be hung ”signboard (see Appendix I). If someone is working on the line, a sign reading “Do not close – someone is working on the line!” should be hung on the operation handles of the line circuit breaker (switch) and the isolating switch (disconnector) ”Signs. In cases where, due to equipment reasons, a circuit breaker (switch) is connected between the grounding switch and the equipment under maintenance, once both the grounding switch and the circuit breaker (switch) are closed, a sign reading “Do not open!” should be attached to the operation handle of the circuit breaker (switch) ”Signs. At the operating positions of circuit breakers (switches) and isolating switches (disconnector switches) that are operated on the display screen, “Do not close – someone is working!” should be indicated accordingly ”Or “Do not close the switch – someone is working on the line!” ”And “Do not open the circuit breaker!” ”The marker. 4.5.2 For work involving partial power outages, temporary barriers shall be installed around the equipment that remains under power and is within a distance smaller than that specified in Table 2-1. The distance between these temporary barriers and the live parts must not be less than the values given in Table 4-1. Temporary barriers can be made of dry wood, rubber, or other durable insulating materials; they must be installed firmly, with signs stating “Stop! High voltage – danger!” attached to them ”Signs. For temporary barriers around equipment at 35 kV and below, if special work requirements dictate it, insulating shields can be used to make direct contact with the live parts. However, such baffles shall have high insulation properties and meet the requirements of Appendix J. 4.5.3 When working on indoor high-voltage equipment, “Stop! High voltage – danger!” signs should be hung on the barriers (fences) surrounding the work area on both sides and opposite the operating equipment, as well as on the barriers (fences) in the areas where access is prohibited ”Signs. 4.5.4 After the pull-out switch in the high-voltage switchgear is drawn out and the baffle that isolates the live parts is closed, it is prohibited to open it, and a sign reading “Stop! High voltage – danger!” must be installed ”Signs. 4.5.5 When working on outdoor high-voltage equipment, a fence should be installed around the work area; the entrances and exits should be located next to nearby roads, with signs stating “Enter and exit from here!” ”Signs. An appropriate number of “Stop, High Voltage Danger!” signs should be hung on the fences surrounding the work area ”Signs: The signs should face inward, toward the fence. If most of the equipment in the outdoor power distribution apparatus is powered down, and only a few locations still have live equipment while there is no possibility of anyone coming into contact with the live conductors, a fully enclosed fence can be installed around the live equipment, with an appropriate number of signs reading “Stop, High Voltage – Danger!” hung on the fence ”Signboard; the signboard should face outward from the fence. It is strictly forbidden to cross the fence. 4.5.6 Set up “Work here!” at the workplace! ”Signs. 4.5.7 When working on an outdoor structure, a sign reading “Stop, high voltage – danger!” should be hung on the beam adjacent to the live parts at the work site ”Signs. When staff are ascending or descending the iron frame or ladder, a sign should be hung that reads “Use this to ascend and descend!” ”Signs. On adjacent live structures that could be mistakenly climbed, a sign reading “No climbing – high voltage, dangerous!” should be hung ”Signs. 4.5.8 Staff are strictly prohibited from moving or removing barriers (fences) and signboards without authorization. 5 Safety measures for substations and power plants during line operations 5.1 The switching on and off of lines shall be carried out in accordance with the instructions of the duty dispatcher or the person authorized to grant line work permits. Scheduled power outages and restorations are strictly prohibited. In the event of a power outage, all circuit breakers (switches) that could supply power to that circuit, as well as the line isolators and busbar isolators, must be switched off first. The pull-out switches should be moved to the testing or maintenance position. After confirming that there is no voltage present, ground wires should be installed at all points on the circuit where power might supply it, or the ground isolators should be closed. A sign reading “Do not close – work is in progress on the line!” should be attached to the operation handles of both circuit breakers (switches) and isolating switches (disconnectors) ”On the signboards, the operation areas of the circuit breakers (switches) and isolators (disconnector switches) on the display screen should be marked with “Do not close – someone is working on the line!” ”The marker. 5.2 The duty dispatcher or line work permit issuer shall record in the logbook the number of work teams carrying out maintenance on the line, the name of the work supervisor, the location of the work, and the tasks to be performed. At the end of the work, a completion report from the person in charge of the work (including the user) is required to confirm that all work teams have finished their tasks, that the grounding wires have been removed, and that all workers have left the area surrounding the lines. Only after verifying this information against the record book can it be ordered that the safety measures in the substation or power plant be removed, allowing electricity to be supplied to the lines. 5.3 When a power outage is required for the lines under the user’s jurisdiction, a written request from the user’s contact person in charge of power supply/disconnection must be obtained; the outage can only be carried out after approval, and appropriate safety measures must be taken. Power supply can be restored only after receiving the completion report from the original applicant, and after making a recording and taking notes. The list of contacts for users to request power outage or restoration should be filed with the dispatching department and relevant authorities. 6 Live Working 6.1 General Provisions 6.1.1 The provisions of this chapter apply to live working carried out at equal potential, intermediate potential, and ground potential on high-voltage overhead power lines with an AC voltage of 10–500 kV at altitudes of 1000 m or less, as well as on electrical equipment in substations (power plants), including low-voltage live working. When performing live work at altitudes above 1000 meters, it is necessary to adjust the safety distances and lengths for various types of air and solid insulation, as well as the number of insulator units, based on the specific altitude of the work area. Safety procedures for live work must be established and implemented only after approval by the person in charge of production at the organization (the chief engineer). 6.1.2 Live working should be carried out in good weather. Live working must not be carried out in the presence of thunderstorms (hearing thunder or seeing lightning), snow, hail, or rain and fog. Generally, live working is not advisable when the wind speed is above level 5. In special circumstances, such as carrying out live repairs in severe weather, relevant personnel should be organized to conduct thorough discussions and develop necessary safety measures; these measures can only be implemented after approval by the unit’s production supervisor (chief engineer). 6.1.3 For new live-working projects that are relatively complex and challenging, as well as newly developed tools, scientific tests must be conducted to ensure their safety and reliability. Operation procedures and safety measures must be formulated, and only after approval by the person in charge of production at the respective unit (the chief engineer) can they be used. 6.1.4 Personnel participating in live work must receive specialized training, pass relevant examinations, and obtain written approval from the enterprise before they can carry out such work. The issuer of the live working work order, the person in charge of the work, and the dedicated supervisor should be individuals with practical experience in live working. 6.1.5 A dedicated supervisor shall be assigned for live working. The guardian shall not operate it directly. The scope of supervision shall not exceed one work site. When working on complex or tall towers, it is necessary to assign an additional (tower) supervisor if required. 6.1.6 When the issuer of the live work permit or the work supervisor deems it necessary, experienced personnel should be sent to the site for an inspection; based on the results of this inspection, a decision should be made as to whether the live work can be carried out, and the method of operation, the tools required, as well as the measures that need to be taken should be determined. 6.1.7 In live working, the reclosing function shall be disabled in any of the following situations, and power shall not be forced to be restored: 6.1.7.1 Operations that may cause a single-phase ground fault in systems with effectively grounded neutral points. 6.1.7.2 Operations that may cause inter-phase short circuits in systems with a non-effective neutral grounding. 6.1.7.3 Tasks for which the work order issuer or work supervisor deems it necessary to disable reclosing. It is strictly prohibited to schedule the shutdown or restoration of reclosing. 6.1.8 Before starting the live working, the person in charge of the live working shall contact the duty dispatcher. Tasks that require the deactivation of reclosing devices, as well as the live cutting and connecting of conductors, must have their authorization procedures carried out by the duty dispatcher. After the live work is completed, it should be reported to the duty dispatcher promptly. 6.1.9 If the equipment loses power suddenly during live working, the workers should assume that the equipment is still live. The person in charge of the work should contact the dispatching officer as soon as possible; the duty dispatcher must not restore power until he or she has contacted the person in charge of the work. 6.2 General safety technical measures 6.2.1 When performing work at ground potential with live electrical equipment, the safety distance between the person and the live parts must not be less than the values specified in Table 6-1. For live equipment at 35 kV and below that fails to meet the minimum safety distances specified in Table 6-1, reliable insulation isolation measures must be taken. Table 6.1 Safe distances between personnel and live conductors during live working Voltage level (kV): 10, 35, 63(66), 110, 220, 330, 500 Safe distance (m): 0.4, 0.6, 0.7, 1.0, 1.8 (1.6), 2.2, 3.4 (3.2) * When it is not possible to maintain a distance of 1.8 m due to equipment constraints, with the approval of the unit’s production manager (chief engineer) and after taking necessary measures, the value in parentheses, namely 1.6 m, may be used. ** Below 500m altitude. A value of 3.2 m is used for 500 kV, but it is not applicable to 500 kV compact lines. At elevations of 500–1000 m, a value of 3.4 m is adopted for 500 kV. 6.2.2 The effective insulation length of insulated operating rods, insulated load-bearing tools, and insulated ropes shall not be less than the values specified in Table 6-2. Table 6.2 Minimum effective insulation length for insulating tools Voltage class (kV) Effective insulation length (m) Insulating operating rods Insulating load-bearing tools, insulating ropes 10 0.7 0.4 35 0.9 0.6 63(66) 1.0 0.7 110 1.3 1.0 220 2.1 1.8 330 3.1 2.8 500 4.0 3.7 6.2.3 Non-insulating ropes (such as cotton yarn ropes, white-brown ropes, steel wire ropes) shall not be used for live working. 6.2.4 When replacing insulators while they are still under voltage or working on insulator strings, it is necessary to ensure that the number of properly insulated insulator units in use is not less than the value specified in Table 6-3. Table 6-3 Minimum number of insulators required for live working Voltage class (kV) 35 63(66) 110 220 330 500 Number of insulators 2 3 5 9 16 23 6.2.5 For operations involving the replacement of straight insulator strings or the movement of conductors, when a single suspension device is used, backup protection measures should be implemented to prevent the conductor from falling off. 6.2.6 Before the insulator string becomes detached from the conductor, when removing or installing the first insulator near the crossarm, special short-circuiting wires or protective shielding suits must be used before direct operation can be carried out. 6.2.7 When performing live work in urban areas or densely populated regions, a fence should be set up at the work site, and a dedicated person should be assigned to supervise it; unauthorized personnel are strictly prohibited from entering. 6.2.8 Unless there is a special need, live wiring installation or removal work should not be carried out beneath crossings or in spans adjacent to power lines or other low-voltage lines. If it is to be carried out, reliable safety measures must be established, and it may only proceed after approval by the production leader (chief engineer) of the unit. 6.3 Equal potential work 6.3.1 Equal potential work is generally carried out on power lines and electrical equipment with voltage levels of 63 (66) kV and above. When performing equipotential work at the 35 kV voltage level, reliable insulation isolation measures must be taken. Equal potential work shall not be carried out on power lines and electrical equipment at voltage levels of 10 kV and below. 6.3.2 Personnel performing equipotential work shall wear a qualified full set of shielding suits outside their regular clothing (including a hat, clothes, pants, gloves, socks, and shoes), and all parts thereof shall be properly connected. Flame-retardant undergarments should also be worn under the protective suit. It is strictly prohibited to interrupt or connect the ground current through shielding suits, as well as the capacitive current in unloaded circuits and coupling capacitors. 6.3.3 The distance between equipotential workers and the ground shall be not less than the values specified in Table 6-1, and the distance between them and adjacent conductors shall be not less than the values specified in Table 6-4. Table 6-4 Minimum distance between equipotential workers and adjacent phase conductors Voltage level (kV): 35, 63(66), 110, 220, 330, 500 Distance (m): 0.8, 0.9, 1.4, 2.5, 3.5, 5.0, 6.3.4 When equipotential workers are working on an insulating ladder or entering a strong electric field along such a ladder, the combined gap formed by the gaps between them and the ground as well as the live conductors must not be less than the values specified in Table 6-5. Table 6-5 Minimum combined clearance for equipotential work Voltage level (kV): 35, 63(66), 110, 220, 330, 500 Distance (m): 0.7, 0.8, 1.2, 2.1, 3.1, 4.0, 6.3.5 Equipotential work is generally carried out on insulator strings with a voltage level of 220 kV and above, where workers move along these insulator strings into strong electric fields. The combined clearance shall not be less than the values specified in Table 6-5. If the requirements in Table 6-5 are not met, a protective gap should be added. After deducting the number of insulator discs with short circuits or zero values, the number of good insulator discs must not be less than the value specified in Table 6-3. 6.3.6 Before potential transfer, personnel performing equipotential work must obtain permission from the work supervisor. When transferring electric potential, the distance between the exposed parts of the human body and the charged object should not be less than the value specified in Table 6-6. 6.3.7 When personnel working at equal potential and those working at ground potential transfer tools and materials, insulated tools or insulated ropes shall be used, and their effective length shall not be less than the value specified in Table 6-2. Minimum distance between the exposed parts of the human body and live conductors during potential equalization work when transferring potential. Voltage level (kV): 35, 63 (66), 110, 220, 330, 500. Distance (m): 0.2, 0.3, 0.4, 6.3.8 For work involving the use of soft or hard ladders or aerial platforms suspended on conductors or ground wires to enter strong electric fields, the following regulations must be followed: 6.3.8.1 When hanging ladders (or aerial platforms) on conductors or ground wires over consecutive spans, the cross-sectional area of such conductors or ground wires must be no less than: 120 for aluminum conductor with steel core and aluminum alloy conductors ； Steel strand 50 (equivalent to OPGW optical cables and the accompanying LGJ-70/40 conductors). 6.3.8.2 In any of the following situations, a calculation must show that it is feasible, and approval from the unit’s production supervisor (chief engineer) is required before proceeding: 1) Work on the conductors and ground wires of an isolated section ； 2) Work on conductors and ground wires with broken strands, as well as on rusted ground wires ； 3) Work on conductors and ground wires of other models other than those specified in 6.3.8.1 ； 4) Work by two or more persons on the same conductor or ground wire in the same category. 6.3.8.3 Before hanging ladders or aerial work platforms on the conductors and ground wires to carry out equipotential work, the tightness of the conductors and ground wires at the towers at both ends of this span should be checked. After loading the ladder, the safe distance between the ground wire and the human body and the live wires below should be 0.5 m greater than the values specified in Table 6-1 ； The safety distance between live conductors and the human body and the power lines, communication lines, and other buildings that are crossed should be 1 m greater than the values shown in Table 6-1. 6.3.8.4 Ladders are strictly prohibited from being used for work on lines with porcelain cross-arms; the cross-arms must be secured before a ladder is placed on lines where the cross-arms can rotate. 6.3.9 During their work, personnel performing equipotential work are strictly prohibited from using flammable substances such as alcohol or gasoline to wipe the live parts and insulated sections to prevent fires. 6.4 Disconnecting and connecting conductors while under voltage 6.4.1 When disconnecting or connecting an unloaded line while under voltage, the following rules must be followed: 6.4.1.1 Before proceeding with such operations, it is necessary to ensure that the circuit breaker (switch) and isolator (disconnector) at the other end of the line are indeed disconnected, and that the transformer and voltage transformer connected to that end of the line have been taken out of service. It is strictly prohibited to disconnect or connect leads under load. 6.4.1.2 When breaking or connecting unloaded lines under voltage, the operators shall wear goggles and arc suppression measures shall be taken. The current-breaking capacity of the arc extinguishing device should be suitable for the voltage level and capacitive current of the unloaded line being disconnected or connected. If an arc-suppression rope is used, the length of the unloaded line at the point of disconnection and connection should not exceed the values specified in Table 6-7, and the workers must maintain a distance of more than 4 meters from the disconnection point. Table 6-7 Maximum length of unloaded lines that can be disconnected or connected using arc-suppression ropes Voltage level (kV): 10, 35, 63, 110, 220 Length (km): 50, 30, 20, 10, 3 Note: The line length includes branches but does not include cable lines. 6.4.1.3 Live wire cutting and lead connection may only be carried out after it has been confirmed that there is no ground fault on the line, the insulation is in good condition, no one is working on the line, and the phase is correct. 6.4.1.4 Wires of the phase that is not connected when making a live connection, and wires of the phase that has been disconnected when breaking a live connection, will become charged due to induction. To prevent electric shock, measures must be taken before personnel can touch it. 6.4.1.5 It is strictly prohibited to touch both ends of an unconnected or disconnected wire at the same time, to prevent the human body from being included in the circuit. 6.4.2 It is strictly prohibited to disconnect or connect an unloaded circuit in order to separate or connect two power sources. 6.4.3 When disconnecting or connecting coupling capacitors while they are charged, their signal and grounding switches should be closed, and the high-frequency protection should be disabled. The disconnected capacitor should be discharged to ground immediately. 6.4.4 When disconnecting or connecting unloaded lines, as well as the leads of devices such as coupling capacitors, arresters, and wave arresters while they are under voltage, measures should be taken to prevent the movement of those leads. 6.5 Live Short-Circuiting Equipment 6.5.1 When using shunt wires to short-circuit current-carrying equipment such as circuit breakers (switches), isolating switches (disconnectors), and drop-out fuses (fuses), the following rules must be followed: 6.5.1.1 The phases must be verified before performing the short-circuiting. 6.5.1.2 The oxide layer at the wires where the shunt line is assembled shall be removed, and the connection between the clamps shall be firm and reliable. 6.5.1.3 The insulation level of the insulating shunts used for equipment at 35 kV and below shall comply with the requirements specified in Table 6-13. 6.5.1.4 The circuit breaker (switch) must be in the closed position, and the fuse in the trip circuit must be removed and the trip mechanism locked before short-circuiting is possible. 6.5.1.5 The shunt lines should be properly supported to prevent swinging from causing grounding or short circuits. 6.5.2 Before the wave blocker is short-circuited, it is essential to prevent personnel performing equal potential work from short-circuiting the wave blocker with their bodies. 6.5.3 The cross-sectional area of the shunt line for the short-circuit switching equipment or wave blocker, as well as the current-carrying capacity of the clamps at both ends, shall meet the requirements of the maximum load current. 6.6 Water flushing under power 6.6.1 Water flushing under power should generally be carried out in good weather. It is not suitable to carry out the activity when the wind force is above level 4, the temperature is below –3°C, or during rainy, snowy, sandstormy, foggy weather, or thunderstorms. During flushing, the operator should wear insulating gloves and insulating boots. 6.6.2 Before carrying out water flushing operations on live equipment, it is necessary to understand the degree of dirtiness of the insulators. When the salt density value exceeds the maximum critical salt density value specified in Table 6-8, water flushing is generally not advisable; otherwise, the resistivity of the water should be increased as a remedy. Lightning arresters and equipment with poor sealing should not be washed with water while energized. 6.6.3 The resistivity of water used for live water flushing should generally be no less than 1500Ω•cm; for flushing 220kV transformer equipment, the resistivity of the water should be no less than 3000Ω•cm, and it must meet the requirements specified in Table 6-8. Before each flushing, the water resistivity should be measured using a qualified water resistance meter, and water samples should be taken from the outlet of the water gun for measurement. If water is collected in containers such as water wheels, the resistivity of the water in each container should be measured. Table 6.8 Critical salt density values for flushing with charged water ① (applicable only to 220 kV and below) Tracking distance ② (mm/kV) For pillar insulators or enclosed porcelain bushings in power plants and substations: 14.8–16 (standard type); 20–31 (anti-fouling type). Critical salt density values: () 0.02, 0.04, 0.08, 0.12, 0.08, 0.12, 0.16, 0.2. Water resistivity (Ω•cm): 1500, 3000, 10000, 50000 and above; 1500, 3000, 10000, 50000 and above. Tracking distance ② (mm/kV) for line suspension insulators: 14.8–16 (standard type); 20–31 (anti-fouling type). Critical salt density values: () 0.05, 0.07, 0.12, 0.15, 0.12, 0.15, 0.2, 0.22. Water resistivity (Ω•cm): 1500, 3000, 10000, 50000 and above; 1500, 3000, 10000, 50000 and above. ① The critical salt density values for voltages of 330 kV and above are not yet established, so they are not included here. ②The creepage distance ratio refers to the ratio of the creepage distance of the external insulation of electrical equipment to the highest operating voltage of the equipment. 6.6.4 Large and medium-sized water jets with a water column as the main insulator (those with a nozzle diameter of 4–8 mm are referred to as medium water jets ； Those with a diameter of 9 mm or more are referred to as large water jets); the length of the water column between the nozzle of such water gun and the charged body must not be less than the value specified in Table 6-9. Both large and medium-sized water gun nozzles should be reliably grounded. Table 6.9 Length of water column between the nozzle and the charged body (m). Nozzle diameter (mm): 4–8, 9–12, 13–18. Voltage level (kV): 63 (66) and below, 2, 4, 6; 110, 3, 5, 7; 220, 4, 6, 8. 6.6.5 Before performing charged cleaning, it is necessary to adjust the pressure of the water pump so that the water column has a long range and a dense flow. When the water pressure is insufficient, the water gun must not be directed at the live equipment being cleaned. The water pump for flushing should be properly grounded. 6.6.6 When using water flushing on live equipment, it is important to choose the appropriate flushing method. For insulators with a larger diameter, the dual-gun tracking method or other methods should be employed, and it is necessary to prevent the formation of water streaks on the surface of the equipment being cleaned. When the insulators to be flushed are not thoroughly cleaned, it is strictly prohibited to stop the flushing process to avoid flashover. 6.6.7 Before performing water flushing while the equipment is energized, it is necessary to confirm that the insulation of the equipment is in good condition. Insulators with zero or low values, as well as those made of porcelain that are cracked, generally should not be rinsed. 6.6.8 When flushing suspended and straining insulator strings as well as porcelain cross-arms, flushing should be carried out sequentially from the conductor side to the cross-arm side. When flushing pillar insulators and insulating porcelain bushings, rinse from bottom to top. 6.6.9 When flushing insulators, attention should be paid to the wind direction; flush the downwind side first, then the upwind side ； For insulators arranged in upper and lower layers, the lower layer should be punched first, followed by the upper layer. Attention must also be paid to the rinsing angle to prevent flashover in the sprayed water mist near the insulators. 6.7 Operation of live-line cleaning machinery 6.7.1 When performing live-line cleaning tasks, the effective length of the insulated operating rod must not be less than the value specified in Table 6-2. 6.7.2 Before using a live cleaning machine for cleaning, it is necessary to ensure that the machine is in good condition (the motor and control components, flexible shafts and transmission parts, etc.); that the insulating parts are free from deformation, dirt, or damage; that the brush rotates in the correct direction; and that the cleaning machine is properly grounded. 6.7.3 Personnel carrying out live-line cleaning operations should work on the upwind side and must wear masks and goggles. 6.7.4 During operation, the operator’s hands should always hold the part of the insulating rod below the protective ring, and ensure that the insulating components used for live cleaning remain clean and dry. 6.8 Protection against induced voltage 6.8.1 When working on utility poles and towers at voltage levels of 330 kV and above, as well as on substation structures, measures to protect against electrostatic induction should be taken, such as wearing anti-electrostatic protective clothing and conductive shoes (it is advisable to wear conductive shoes when working on 220 kV utility pole and towers). 6.8.2 Insulated overhead ground wires shall be regarded as live parts. When working near an insulated overhead ground wire, the distance between the worker and the insulated overhead ground wire should not be less than 0.4 m. When working on insulated overhead conductors, it is necessary to reliably ground them using a grounding wire or to employ equipotential bonding. 6.8.3 When transferring large metal items (including tools, materials, etc.) using insulated ropes, workers on the tower or on the ground should ground the metal items before touching them to prevent electric shock. 6.9 Operation of overhead insulated boom trucks 6.9.1 Overhead insulated boom trucks must pass inspection. Crane operators should be familiar with the relevant regulations for working on live circuits, receive specialized training, pass the examinations, and work with a valid certificate. 6.9.2 The working position of the overhead insulated boom truck should be selected appropriately, the support should be stable and reliable, and anti-tilting measures should be in place. Before use, perform a test operation with an empty bucket at the designated location to ensure that the hydraulic transmission, rotation, lifting, and telescoping systems are functioning properly and operate smoothly, as well as that the braking system is reliable. 6.9.3 Workers in insulated buckets shall use safety belts and insulated tools properly. 6.9.4 Operators of overhead insulated boom trucks shall follow the instructions of the work supervisor, and pay attention to the surrounding environment and operating speed during operations. During operation, the engine of the overhead insulated boom truck must not be turned off. When approaching and moving away from live parts, the operation should be carried out by the person in the boom, but the operator at the lower position must not leave the control console. 6.9.5 The effective insulation length of the insulated arm shall be greater than the value specified in Table 6-10, and a leakage current monitoring device shall be installed at its lower end. Table 6-10 Minimum effective insulation length of the insulating arm. Voltage class (kV): 10, 35, 63 (66); 110, 220. Length (m): 1.0, 1.5, 2.0, 3.0, 6.9. During the upward rotation of the lower section of the insulating arm, the distance to live parts shall be increased by 0.5 m compared to the values specified in Table 6-1. The vehicle body must be properly grounded during operation. 6.10 Protection gaps 6.10.1 The grounding wire for protection gaps shall be made of multi-strand soft copper wire. Its cross-section shall meet the requirements for grounding short-circuit capacity, but shall not be less than 25. 6.10.2 The distance of the arc-shaped protective clearance shall be set in accordance with the provisions of Table 6-11. Table 6-11 Setting values for arc-shaped protective gaps Voltage level (kV): 220, 330 Gap distance (m): 0.7–0.8, 1.0–1.1, 6.1–10.3 When using protective gaps, the following rules must be followed: 6.10.3.1 Before installing the protective gap, it is necessary to contact the dispatching office to disable reclosing. 6.10.3.2 The suspension protection gap should first be reliably grounded to the grounding grid, and then the protection gap should be hung on the conductor with good contact. The procedure for demolition is the opposite. 6.10.3.3 The protective gap should be installed on the conductors of adjacent towers; after installation, a dedicated person should be assigned to monitor it, and fences should also be installed in areas where people or animals may pass through. 6.10.3.4 Personnel installing or removing the protection gap shall wear a full set of shielding suits. 6.11 Insulator testing under voltage 6.11.1 When using a spark gap detector to test insulators, the following rules shall be followed: 6.11.1.1 The detector should be tested prior to use to ensure smooth operation and accurate measurements. 6.11.1.2 Pin-type and suspension insulators with fewer than 3 discs shall not be inspected using a spark gap detector. 6.11.1.3 When testing insulator strings at voltage levels of 35 kV and above, if the number of zero-value insulator units in the same string reaches the value specified in Table 6-12, testing must be stopped immediately. Table 6-12: Number of zero-value insulator units allowed in a string. Voltage level (kV): 35, 63(66), 110, 220, 330, 500. Number of insulator units in the string: 3, 5, 7, 13, 19, 28. Number of zero-value units: 1, 2, 3, 5, 4, 6. If the number of insulator units in a string exceeds the values specified in Table 6-12, the allowable number of zero-value insulators can be increased accordingly. 6.11.1.4 It should be carried out on dry weather. 6.12 Low-voltage live working 6.12.1 Special personnel shall be assigned to supervise low-voltage live working. 6.12.2 Use tools with insulated handles; the exposed conductive parts of such tools should be insulated to prevent short circuits between phases or to ground during operation. When working, one should wear insulated shoes and 100% cotton long-sleeved work clothes, as well as gloves, a safety helmet, and goggles, and stand on dry insulating surfaces. The use of files, metal rulers, and brushes or dusters containing metal is strictly prohibited. 6.12.3 When high-voltage and low-voltage lines are installed on the same pole, when working on the low-voltage lines, it is necessary to first check the distance from the high-voltage lines and take measures to prevent accidental contact with the live high-voltage equipment. When low-voltage live wires lack insulation measures, workers must not cross them. When working on live low-voltage distribution equipment, insulation isolation measures should be taken to prevent phase-to-phase short circuits and single-phase grounding. 6.12.4 Before ascending the pole, identify the phase and neutral wires first, and select the appropriate working position. When disconnecting wires, the phase wire should be disconnected first, followed by the neutral wire. When connecting wires in overlap, the order should be reversed. The human body must not come into contact with two wire ends at the same time. 6.13 Storage, Use, and Testing of Live Working Tools 6.13.1 Storage of Live Working Tools: 6.13.1.1 Live working tools shall be stored in a dedicated tool room that is well-ventilated, clean, and dry. The doors and windows of the tool room should be tightly sealed, and the floor, walls, and ceiling should be made of dust-free, flame-retardant materials. The relative humidity indoors should be maintained at 50% to 70%. The indoor temperature should be slightly higher than the outdoor temperature, and it should not be lower than 0°C. 6.13.1.2 When ventilating the tool room where live electrical equipment is stored, it should be done on dry days, and the relative humidity outside must not exceed 75%. After ventilation is completed, the relative humidity inside the room should be checked immediately and adjusted as necessary. 6.13.1.3 The live working tool room should be equipped with: hygrometers, thermometers, dehumidifiers (in quantities sufficient to meet the requirements), heaters that provide even heating, adequate tool racks, hangers, and fire extinguishers, etc. 6.13.1.4 Live working tools shall be uniformly numbered, kept by designated personnel, registered, and records of testing, maintenance, and use shall be maintained. 6.13.1.5 Defective live working tools shall be repaired promptly, and those that do not meet the standards shall be scrapped immediately; continued use is strictly prohibited. 6.13.1.6 Elevated insulated boom trucks should be stored in a dry and well-ventilated garage, with moisture-proof measures in place for their insulated parts. 6.13.2 Use of live working tools: 6.13.2.1 Live working tools shall have good insulation, firm connections, and smooth operation, and shall be used in accordance with the manufacturer’s instructions and on-site operating procedures. 6.13.2.2 Before using live working tools, it is necessary to verify that they meet the specified safety factor based on the workload. 6.13.2.3 During transportation, live insulating tools shall be placed in specialized tool bags, tool boxes, or dedicated tool vehicles to prevent moisture damage and wear. If it is found that insulating tools are damp, have surface damage, or are dirty, they should be dealt with promptly, and can only be used after passing relevant tests or inspections. 6.13.2.4 When entering the work site, the live working tools to be used should be placed on moisture-proof canvas or insulating pads to prevent the insulating tools from getting dirty or damp during use. 6.13.2.5 Before using live working tools, carefully inspect to ensure there is no damage, moisture, deformation, or malfunction; otherwise, their use is prohibited. Segmental insulation testing shall be carried out using a megohmmeter or insulation tester of 2500V or higher (with electrode width of 2cm and spacing between electrodes of 2cm), and the resistance value should be no less than 700MΩ. Clean, dry gloves should be worn when operating insulated tools. 6.13.3 Testing of live working tools: 6.13.3.1 Live working tools shall be subject to electrical and mechanical testing on a regular basis. The testing schedule is as follows: Electrical testing – preventive testing once a year, inspection testing once a year, with a gap of six months between the two types of testing. Mechanical testing: Insulated tools once a year, metal tools every two years. 6.13.3.2 The electrical preventive testing items and standards for insulating tools are shown in Table 6-13. Table 6-13 Test items and standards for insulating tools. Rated voltage (kV), Test length (m), Power-frequency withstand voltage for 1 min (kV), Power-frequency withstand voltage for 5 min (kV), Withstand voltage under operational impulse for 15 times (kV). Tests: Factory and type tests, Preventive tests – Factory and type tests, Preventive tests, Factory and type tests, Preventive tests. 10: 0.4; 100: 45; 35; 0.6; 150: 95; 63(66); 0.7: 175: 175; 110; 1.0: 250: 220; 220; 1.8: 450: 440; 330; 2.8: –; –: 420; 380; 900: 800; 500; 3.7: –; –: 640; 580; 1175: 1050. For the operational impulse withstand voltage test, a standard wave of 250/2500 μs should be used, and success is deemed to be achieved if there is no breakdown or flashover. The power-frequency withstand voltage test is considered successful if there is no breakdown, no arcing, and no overheating. The high-voltage electrode should be a metal tube with a diameter of not less than 30 mm; the test specimen should be hung vertically, and the distance between the grounding electrode and the ground should be 1.0 to 1.2 meters. At the grounding electrode and the electrode connected to high voltage (when without fittings), it is wrapped with 50 mm wide metal platinum. The distance between test specimens should be no less than 500 mm; the diameter of the voltage equalizing balls on both sides of each single wire should be no less than 200 mm, and the distance between these voltage equalizing balls and the test specimens should be no less than 1.5 m. The test sample shall be tested as a whole, without being divided into sections. 6.13.3.3 The test conditions for inspecting insulating tools are as follows: the insulating tool is divided into several sections for power-frequency withstanding voltage tests, with a voltage of 75 kV applied per 300 mm for a duration of 1 minute; success is deemed to be achieved if there is no breakdown, arcing, or overheating. 6.13.3.4 The electrical testing standards for live-working overhead insulated boom trucks are provided in Appendix K. 6.13.3.5 The water flushing tools for composite insulation shall undergo electrical testing while in operation. In addition to the tests specified in Table 6-13 according to the relevant items and standards (for voltage levels of 220 kV and below), a power-frequency leakage test shall also be conducted; the test voltage is given in Table 6-14. The leakage current is considered acceptable if it does not exceed 1mA. The test duration is 5 minutes. The water resistivity during testing was 1500Ω•cm (suitable for voltage levels of 220 kV and below). Table 6-14: Power-frequency leakage test voltage values for water flushing tools used with composite insulation. Rated voltage (kV): 10, 35, 63(66), 110, 220. Test voltage (kV): 15, 46, 80, 110, 220. 6.13.3.6 The resistance value between any two endpoints of the shielding suit shall not exceed 20Ω. 6.13.3.7 Mechanical test standards for live working tools: 1) When bearing the loads of various clamps and connection fittings under operating load conditions, tests shall be conducted in accordance with the relevant fitting standards. 2) When other static loads are applied under working load conditions, tests shall be conducted in accordance with the design loads and the provisions of SD 165 \"Basic Requirements for the Design of Construction Equipment in Electric Power Construction (Part on Transmission Line Construction Equipment)\". 3) When bearing the operational load under working load conditions: Static load test: 2.5 times the allowable working load for 5 minutes; the tool is considered qualified if it shows no deformation or damage. Dynamic load test: Operate the tool 3 times at 1.5 times the allowable working load; it is considered qualified if it remains flexible, lightweight, and free from any jamming.