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Abstract: Taking into account the actual characteristics of work in substation operation, this approach emphasizes preventing misoperations, strengthening inspections of equipment, and carrying out prompt and proper accident handling, in order to effectively ensure the safety of the power grid, the equipment, and personnel； The relevant measures and requirements outlined in this document are based on substation operation specifications, on-site operation procedures, power grid dispatching regulations, electrical safety work procedures, and other relevant rules. They enable proactive prevention and effective control, are practical, and highly actionable ； In response to frequent accidents, focus on prevention. Keywords: substation operation, hazard points, analysis, countermeasures. 1 Introduction A substation is a facility in the power system where electrical energy is received and distributed, as well as where voltage is transformed. It serves as an intermediary link between power plants and electricity consumers, and it connects power grids at different voltage levels through transformers, thereby ensuring the safety and stability of the power grid as well as reliable power supply for consumers. Based on the importance of their location, there are hub substations and local substations. Misoperations can cause significant harm to power grids, equipment, and society. Therefore, the responsibilities associated with substation operation are significant; it is crucial to carry out effective safety management in substations to ensure the safe operation of the power grid and equipment. Substation operation supervisors must earnestly implement the safety guideline of \"safety first, prevention first.\" Given the importance of the substation’s location, they should carry out thorough analyses of potential hazards in the substation and take preventive measures to ensure that accidents can be prevented in advance, thus guaranteeing the safe operation of the substation. 2 Hazard analysis and preventive measures 2.1 Preparation of switching operation tickets Hazard: Errors in the preparation of switching operation tickets. Based on the operating status of the equipment, there are four states: in operation, in hot standby, in cold standby, and under maintenance. For an equipment to transition from one state to another, it is necessary to fill out a switching operation ticket. This ticket serves as the basis for carrying out switching operations in the power grid, and its accuracy is directly related to preventing errors in operations, thereby ensuring the safety of the power grid, the equipment, and personnel. Accident cases over the years have also proven this point: once incorrect operation tickets are carried out, it can lead to equipment damage or even casualties, or it may cause the generator set to be disconnected from the system, triggering a series of chain reactions that result in large-scale power grid failures. Control measures: ● Before preparing the operation ticket, the dispatch order should be carefully checked to clarify the purpose of the operation based on the issued order. For some large-scale and complex grid operations such as those involving busbars, main transformers, bypass circuits with outgoing lines, or the switching on and off of main transformers, operation tickets should be prepared based on the main wiring diagram, relay protection settings, and parameter sheets. ●The issuer, supervisor, and person in charge of duty shall carefully review the filled-out operation ticket, and verify the listed operation items against the simulation panel and secondary circuit diagram to ensure accuracy. ●For some large-scale operations, the operation ticket must be reviewed by the shift leader; special attention should be paid to the switching of secondary circuit switches, such as those used during switch maintenance, for fail-safe starting of bus differential switches, and for operating the terminals in the CT current circuit. ●For the operation of bypassing with a connecting line, make sure that the switch originally used on that bus is matched with the bypass switch; verify that the settings are changed correctly. Pay attention to the adjustments required for the CT circuit, and for high-frequency protection as well. Before pulling out the connecting line switch, ensure that the negative connection of the bypass switch is in order, and switch the corresponding switch to the maintenance mode. ● When bypassing is used in conjunction with a main transformer, pay attention to whether the CT circuit uses a switch-mounted CT or a CT mounted on the bushing; also ensure that the differential protection is disabled. ● Optimize the sequence of operations to avoid any omissions, and use scheduling and operational terminology correctly. Special attention is paid to avoiding excessive walking during the operation. ●Fully consider the impact on the system caused by changes in system power flow, voltage, short-circuit capacity, etc., during switching operations; be familiar with the usage requirements of relay protection and automatic devices, and use them correctly. In case of any doubts, contact the relevant personnel promptly. ● When performing restoration operations, refer to the previously executed shutdown operation tickets. ● Continuously enhance knowledge acquisition and accumulation to improve professional skills. 2.2 On-site Operations Hazard points: Failing to carefully verify the name of equipment during operations, entering the wrong bay, using the wrong setting on the multimeter for measuring protection settings, improperly unlocking devices using anti-error mechanisms, and failing to strictly follow the procedures for verifying voltage and grounding. Control measures: ● After receiving instructions from the dispatch, conduct a verification rehearsal based on the primary wiring diagram; use the anti-error system correctly during operations, following the principle of “first check, second observe, third verify, fourth operate.” ● Before carrying out switching operations, verify the operating status of the equipment on-site. ● Before such operations, carefully consider their impact on system power flow, voltage, relay protection, and automatic devices. ● For large-scale and complex operations, anticipate possible accidents in advance. ● During operations, strictly adhere to the procedures for giving commands, repeating them, reporting progress, keeping records, recording audio, and providing supervision. If an accident occurs while following the operation ticket, stop the operation immediately, assess the situation, and only resume operations after the accident has been resolved. ● Follow the sequence specified in the operation ticket strictly; it is forbidden to omit steps, add steps arbitrarily, or skip steps improperly. ● If the anti-error mechanism malfunctions during electrical operations, stop the operation immediately and report it to the on-duty supervisor. Only after confirming that everything is correct and obtaining approval from the shift supervisor of the substation can unlocking operations be carried out, with proper documentation kept. ●When using a voltage measuring protector, it is necessary to check whether the correct setting is selected; if voltage is being measured while the protector is in use and the device is set to the resistance mode, this can cause the switch outlet to trip. ● It is essential to strictly follow the procedures for testing for electricity and establishing grounding. Insulating gloves must be worn, and contact-type voltage testers suitable for the corresponding voltage level and of qualified quality should be used for testing. Each phase should be tested separately at the points where grounding wires are installed or grounding switches are closed. ●Before performing the bus transfer operation, pay attention to adjusting the operation mode of the bus differential protection; set the bus tie switch to automatic mode, and ensure that all loads have been transferred to the other bus. Before closing the bus tie switch, first operate the secondary air switch of the voltage transformer on the bus that is to be de-energized, and then close the bus tie switch. ● Carefully verify the names and numbers of the equipment to prevent accidental opening or closing of switches and accidental entry into live areas. 2.3 The work order must be correct, and the on-site permission system must be strictly followed. Potential hazards include: work tasks specified in the work order not matching the actual work to be carried out, which could lead to an expansion of the workload; unclear instructions regarding on-site safety measures and live areas, resulting in personnel entering live areas accidentally. ● Thoroughly review the work order – the duty personnel are responsible for checking whether the safety measures listed in the work order are correct and complete, as well as whether they suit the conditions at the site ； Check whether the safety measures in the work site are adequate, and supplement them if necessary ； Responsible for checking whether the maintenance equipment poses a risk of sudden power restoration ； Even if there is the slightest doubt regarding the contents listed in the work order, it is necessary to clarify things with the person who issued the work order; if needed, detailed additional information should be requested. ● The on-site permission system must be strictly followed – together with the person in charge of the work, the safety measures taken should be checked again at the site, and specific isolation procedures should be specified for each piece of equipment to confirm that there is no voltage present in the equipment being repaired. 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. The person in charge of the work and the worker confirm and sign on the work order respectively. 2.4 Submission of equipment maintenance request forms: Risk – The area designated for power outage in the request form does not match the actual work to be carried out, resulting in an expansion or reduction of the area affected by the power outage ； The equipment maintenance requests were not submitted completely; some tasks were carried out without any corresponding requests. Control measures: ● Strictly follow the approval process for equipment maintenance requests – all personnel in the substation must carefully review them and make corrections promptly if any errors are found. Keep signs of insecurity at bay from the very beginning. ● Strictly enforce the two types of work permits and the three systems; work on equipment during regular maintenance must not be carried out without proper permits. 2.5 Equipment Acceptance System: Risk point – When carrying out equipment acceptance, it is necessary to conduct a thorough inspection in accordance with the details of the equipment to be repaired. During the transmission tests as part of this acceptance process, failure to carefully verify the equipment’s name and number has led to repeated incidents of accidentally turning switches on or closing them while a ground wire is still connected. Last year, during equipment inspection at a substation in Jiangsu, the staff failed to verify the equipment carefully; as a result, a switch that was supposed to remain in the closed position was accidentally activated, causing a power outage across the entire station. There were also cases where operators accidentally entered live compartments during inspections, resulting in electric shock accidents, which serve as a very sobering lesson. To ensure the safety of personnel and equipment, a strict equipment acceptance system must be implemented. Control measures: ● When inspecting equipment, carefully verify its name and serial number. ● During transmission tests, check the equipment’s serial number together with the maintenance personnel. ● At least two people should be involved when checking the synchronization of circuit breakers; safety belts must be worn when climbing on the equipment framework to prevent falls from heights. ● Carefully verify the protection settings to avoid errors in their adjustment, ensure that the protection switches are set correctly, and that the setting values are in the proper range. ● Only after a thorough and comprehensive inspection confirming compliance can the work order completion procedures be carried out. 2.6 Review of switching operation tickets: Risk factors include a lack of responsibility in reviewing operation tickets or excessive trust in the person who prepared them, which can result in incorrect operation tickets going unchecked. Control measures: ● According to the dispatch orders and in light of the actual operation mode, clarify one’s thoughts before reviewing the operation tickets as required. ● Review each word, sentence, and item carefully, and assess the necessity and correctness of each operation listed in the operation ticket based on the actual conditions of the system. ● The person taking over from the previous shift must thoroughly review all the operation tickets left over from that shift. 2.7 Handling of grid accidents: Risk points include unclear understanding of the grid’s operation mode during an accident, incorrect judgments, out-of-sync switching, and failure to handle accidents in accordance with established procedures. Control measures: ● Accident handling must be carried out in accordance with the prescribed procedures ； ●When dealing with an accident, it is necessary to understand the circumstances of the accident promptly and comprehensively, as well as determine the operation status of primary equipment, relay protection systems, and automatic devices, in order to make correct judgments. ●Adhering to the principles of protecting personnel, equipment, and the power grid, no impact shall be caused on devices or personnel that are still powered during the handling process, in order to prevent the expansion of accidents. ● Under normal operating conditions, when a fault occurs on the busbar—such as porcelain insulator flashover, arrester explosion, or busbar grounding—the busbar differential protection will activate and disconnect all switches connected to the faulty busbar. At this point, the operator must immediately determine the situation and report it to the on-duty dispatcher; it is absolutely not allowed to restore power to the faulty busbar without first conducting an inspection, in order to prevent the accident from spreading. ● When active circuits are connected in parallel, synchronous switching should be used to ensure that voltage, frequency, and phase are within acceptable ranges. Synchronous switching helps prevent asynchronous switching, which could lead to disconnection of the power grid. ●Locate the fault point and isolate it promptly. After isolating the fault point, it is necessary to confirm that there are no other fault points, then re-enable the bus differential protection. Upon orders from the on-duty dispatcher, the bus coupler switch is used to attempt to restore power to the faulty bus; during this attempt, the charging protection of the bus coupler switch must be activated, and it is essential to first check that the settings of the charging protection as well as the position of the relevant switches are correct. After successful charging, the charging protection is disabled to restore power supply to the de-energized bus. ●If the fault point cannot be isolated promptly, such as in the case of a flashover in the busbar insulators, all outgoing lines on the faulty busbar should be switched to operate on the non-faulty busbars according to the dispatcher’s instructions. At the same time, the corresponding current terminals must be adjusted accordingly to match the primary circuit conditions. ●Busbar power failure faults also include busbar power loss, which refers to the situation where the busbar loses its power supply despite being free of any faults. Generally, due to an external fault, the switch that should trip fails to do so, resulting in a cascade trip that shuts off all the switches on the busbar to which that switch is connected. At this point, it is necessary to quickly determine the nature of the fault; once it is confirmed that there is no fault on the busbar and that there is no voltage in the circuit of the faulty switch, approval from the dispatch center must be obtained before opening the disconnectors on both sides of the faulty switch to isolate it. After the isolated busbar has been recharged using the bus coupler switch, the interrupted circuit can be brought back online. ●In emergency situations where an accident occurs and unlocking is necessary, the circuit breaker can be unlocked with the approval of the on-duty shift supervisor at the substation; during such operations, it is necessary to verify them by referring to the recorded instructions. ● Full consideration must be given to maintaining the continuity of power supply to important users. Regarding the handling of some major accidents, it is necessary to report to the relevant supervisors in a timely manner. 2.8 Shift Handover: Risk points include changes in important grid configurations, major operations, and unclear handovers of work tasks. Control measures: ● Strictly enforce the substation shift handover system; during the handover period, all normal operational communications shall be suspended (except in special cases). ● The incoming crew should carefully read various records, check the simulation panels, listen to the instructions from the departing crew, and clarify any doubts. ● The departing crew must provide the incoming crew with detailed information on the progress of operations and maintenance work, the operating mode, power flow distribution, any changes in protection and automatic control systems, system defects, accidents, and abnormalities, as well as the status of planned tasks, the locations where safety measures have been implemented, and work orders. Ensure clear communication when delivering and understanding when receiving. 2.9 Fire protection: Hazard point – fire. Control measures: ● Regularly inspect the switches and power cords of electrical equipment in the control room, such as air conditioners, relay protection devices, and automation systems; any defects found should be corrected immediately ； ●Fire-fighting equipment is equipped in accordance with standards, regularly inspected, and stored in designated locations; any defective equipment is promptly reported to the security department for replacement, and all on-duty personnel are trained to use it correctly. 2.10 Improper use of the microcomputer-based anti-misoperation system ● Back up the relevant information on the primary electrical equipment in the anti-misoperation device’s main unit. When information changes, backups must be updated promptly. Information backups should be stored on external media such as tapes, disks, or optical discs to meet the recovery requirements in case the main unit of the error prevention device fails. ●Formulate management methods for the mainframe database of error prevention devices and password permissions. ●The main unit of the error prevention device cannot be used in conjunction with office automation systems, and it is strictly prohibited from being connected to the Internet; its network security requirements are equivalent to those of the real-time control systems in power grid secondary systems. ●For the microcomputer-based anti-misoperation locking device: on-site operations are carried out using a computer key; after the operations are completed, the current status information stored in the computer key must be sent back to the main unit of the anti-misoperation device to update its status, thereby ensuring consistency between the status of the main unit and that of the on-site equipment. 3 Conclusions Conducting hazard analysis and preventive control is a key aspect in strengthening safety management in production; it is an important measure to ensure safe production, and it was also a priority in safety production efforts in 2005. By carrying out hazard analysis and preventive control efforts, the goal is to establish strict safety procedures and comprehensive safety rules, raise employees’ safety awareness, improve their skills, and foster a positive safety atmosphere as well as a corporate safety culture. By applying modern management methods and tools, process control can be further strengthened, gaps can be more thoroughly addressed, and potential hazards can be completely eliminated, thereby achieving the ultimate goal of zero violations and zero accidents.