11 Essentials Every Low-Voltage Electrical Technician Should Know

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11 Essentials Every Low-Voltage Electrician Should Know 1. Why must light switches be connected to the live wire? If the lighting switch is installed on the neutral wire, although the light does not turn on when it is switched off, the live wire connected to the lamp socket remains connected. People, thinking the light is not working, mistakenly assume that the power is off. In reality, the voltage of each point on the lighting fixture relative to ground remains at the dangerous level of 220 volts. If people touch these actually charged parts when the light is off, it can cause an electric shock accident. Therefore, for various lighting switches or switches for single-phase low-power electrical devices, they must be connected in series to the live wire to ensure safety. 2. How should a single-phase three-hole socket be installed correctly? Why? Generally, single-phase electrical equipment, especially portable electrical equipment, should use a three-pin plug and a corresponding three-hole socket. Three-hole sockets are equipped with a dedicated protective earth pin; when earth protection is used, it is common for people to simply connect this pin directly to the neutral wire that enters the socket, which is extremely dangerous. Because in the event that the neutral wire of the power supply is disconnected, or if the live (phase) wire and the neutral wire are connected incorrectly, the metal parts such as the casing will also acquire the same voltage as the power supply, which can lead to electric shock. Therefore, during wiring, the dedicated grounding socket should be connected to the dedicated protective ground wire. When zero grounding protection is used, the zero wire should be brought in specifically from the power source, rather than using the zero wire of the plug nearby. 3. Why is it strictly prohibited to bury plastic-insulated wires directly in walls? (1) Over time, as plastic-insulated wires are used, the plastic deteriorates and cracks, resulting in a **reduced level of insulation. This makes the insulation more prone to damage when the circuit is overloaded or short-circuited for short periods of time. (2) Once the wall becomes damp, it can cause widespread electrical leakage, posing a risk to human safety. (3) Directly burying plastic-insulated wires makes it difficult to carry out maintenance and repair of the wiring. 4. Why should a leakage protector be used? A leakage protector, also known as a leakage circuit breaker, is a new type of electrical safety device. Its main functions are: (1) to prevent electric shock accidents caused by leakage in electrical equipment and wiring. (2) Prevent single-phase electric shock accidents during electricity use. (3) Promptly cut off single-phase ground faults during the operation of electrical equipment to prevent electrical fire accidents caused by leakage current. (4) As people’s living standards improve and the number of household appliances increases, electrical accidents such as electric shocks and fires occur during power usage due to defects in the electrical equipment itself, improper use, or inadequate safety measures. These accidents cause unnecessary losses to people’s lives and property. The advent of residual current devices provides a reliable and effective means to prevent such accidents by cutting off the power supply promptly and protecting both equipment and human safety. 5. What are the main causes of electric shock accidents? Statistical data show that the main causes of electric shock accidents are as follows: (1) Lack of knowledge regarding electrical safety, such as flying kites near high-voltage lines or climbing onto high-voltage poles to remove bird nests ； Picking up the live wire by hand without shutting off power after a low-voltage overhead line breaks ； A worker in the dark touches a live electrical conductor ； Touch the damaged rubber-covered knife switch with your hand. (2) Violating operating procedures by connecting circuits or electrical equipment while they are under voltage, without taking the necessary safety measures ； Touch damaged equipment or wires ； Accidental contact with live equipment ； Lighting fixtures with live connections ； Repairing power tools while they are powered on ； Electrical equipment moving under power ； Twist light bulbs with wet hands, etc. (3) The equipment is substandard, and the safety distance is insufficient ； Excessively high grounding resistance in the two-line one-ground system ； The ground wire is defective or disconnected ； Insulation failure, wires exposed, etc. (4) Equipment is in poor condition; strong winds cause lines to be broken or utility poles to fall down, and these issues are not repaired in a timely manner ； The bakelite of the rubber-covered circuit breaker was damaged and not replaced in a timely manner ； The motor wires are damaged, causing the enclosure to remain charged for an extended period ； The porcelain insulator was damaged, causing the phase wire to short-circuit with the pull wire, resulting in the equipment enclosure becoming charged. (5) Other accidental causes, such as walking at night and coming into contact with live wires that have fallen to the ground. 6. What first aid measures should be taken in case of an electric shock? In the event of an electric shock accident, while ensuring the safety of the rescuer themselves, it is necessary first to try to remove the person who has been shocked from the power source as quickly as possible, and then carry out the following emergency repairs. (1) Remove tight clothing that is hindering the person who has suffered an electric shock from breathing. (2) Examine the electrocuted person’s mouth, clear any mucus from it, and remove any dentures if present. (3) Provide immediate on-site first aid; if breathing has stopped, perform mouth-to-mouth resuscitation. If the heart has stopped beating or is experiencing irregular rhythms, perform artificial chest compressions. It must never be interrupted without reason. If there is a second person present at the scene in addition to the rescuer, the following actions should also be taken immediately: 1) Provide first-aid tools and equipment. 2) Disperse unauthorized personnel at the site. 3) Ensure sufficient lighting at the site and maintain good air circulation. 4) Report to the supervisor and ask a doctor to come for emergency treatment. Experimental studies and statistics show that if treatment is initiated 1 minute after an electric shock, 90% of cases can be saved ； If resuscitation begins 6 minutes after an electric shock, there is only a 10% chance of survival ； If resuscitation begins 12 minutes after an electric shock, the chances of survival are extremely low. Therefore, when someone is found to have been electrocuted, every second counts, and every possible measure should be taken. 7. What are the measures for safe electricity use at home? With the widespread use of household appliances, it is crucial to have a proper understanding of electrical safety practices in order to ensure safe electricity use. (1) Do not purchase counterfeit and substandard household products with no manufacturer, address, or quality certification. (2) When using household appliances, there should be complete and reliable power cord plugs. Household appliances with metal casings must be equipped with grounding protection. (3) Switches and fuses must not be installed on the ground wire and neutral wire. It is prohibited to connect the grounding wire to water supply or gas pipelines. (4) Do not touch live equipment with wet hands, and do not wipe live equipment with a wet cloth. (5) Do not pull wires randomly or connect them improperly, and do not move powered equipment casually. (6) When checking and repairing household appliances, the power supply must be turned off first. (7) If the power cord of a household appliance is damaged, it should be replaced immediately or wrapped properly with insulating cloth. (8) In the event of a fire involving household appliances or wires, the power supply should be turned off first before attempting to extinguish the fire. 8. How to prevent household appliances from being damaged by overheating? The rated voltage of common household appliances is 220 volts, and the normal supply voltage is around 220 volts. When the supply voltage rises momentarily in the power supply lines due to natural disasters such as lightning strikes, when there is an imbalance in the three-phase load or when the wires become damaged over time and result in a loss of one of the phases, or when the phase voltage increases due to human errors in wiring, this increase in voltage leads to an increase in current, which in turn causes household appliances to overheat and get damaged. To prevent household appliances from being damaged by overheating, the following measures should be taken: First, unplug electrical devices when they are not in use whenever possible ； The second is to upgrade the old and damaged service lines ； Third, install a leakage circuit breaker with overvoltage protection. 9. How should fuses be selected for residential use? Fuses for residential use should be selected based on the electrical load capacity. If a meter with a capacity of 5 amps is used, the fuse should be greater than 6 amps and less than 10 amps ； When using a meter with a capacity of 10 amps, the fuse should be greater than 12 amps and less than 20 amps; in other words, the fuse chosen should be 1.2 to 2 times the capacity of the meter. The fuse to be used must be a compliant one; it is not allowed to use multiple fuses with lower capacity, nor can copper wire be used as a substitute for a fuse. 10. What are the basic requirements for residual current devices? Technically, the following requirements must be met: (1) The sensitivity of the electric shock protection must be appropriate; generally, the starting current should be within the range of 15 to 30 milliamps. (2) The operating time of the electric shock protection should generally not be greater than 0.1 seconds. (3) The protector should be equipped with the necessary monitoring devices to prevent it from losing its protective function when the operating conditions change; for example, voltage-type electric shock protectors should be fitted with a zero-line grounding device. 11. How to prevent electrical fire accidents? What to do after a fire breaks out? First of all, when installing electrical equipment, it is necessary to ensure quality and meet all safety and fire prevention requirements. Qualified electrical equipment must be used; damaged switches, light fixtures, and broken wires are not permissible. Wire connections must be made securely in accordance with the specified methods, and insulated tape should be used to cover them. The screws connecting the wiring posts and terminals must be tightened to prevent poor contact caused by loose wiring. Just because an electrician has installed the equipment does not mean that the work is complete forever; during use, if the user notices that the wiring of light fixtures or sockets is loose (especially with the wiring of portable appliances, which tends to become loose), there is poor contact, or overheating occurs, they should seek the help of an electrician to address the issue promptly. Secondly, do not place flammable materials such as oils, cotton, wood shavings, and wood near low-voltage circuits, switches, sockets, and fuses. Before an electrical fire occurs, there are always warning signs that require special attention. First, the insulation covering of the wires burns due to overheating, releasing an unpleasant smell similar to that of burning rubber or plastic. Therefore, when this odor is detected, one should first consider that it might be caused by an electrical issue. If no other causes can be found, the power supply should be cut off immediately. Power can only be restored after the cause has been identified and properly addressed. In the event of a fire, whether it is caused by electrical issues or not, the first thing to do is to quickly cut off the power supply in the area affected by the fire. Because if the fire is caused by an electrical issue, cutting off the power supply also cuts off the source of the fire ； Even if a fire is not caused by electrical issues, it can still damage the insulation of wires. If the power supply is not turned off, the damaged wires can cause short circuits, leading to fires in a larger area of wires. In the event of an electrical fire, soil or sand should be used, or a fire extinguisher; foam extinguishers must never be used, as such extinguishing agents are conductive.