Electrician's low-voltage electric shock and safe operation technology - Solutions - Huaqiang Electronic Network

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When an electrician is inspecting a low-voltage electrical installation, there are two types of work-related accidents that are prone to occur, namely, electric shock accidents and high-altitude falls. Among them, high-altitude falls are often caused by electric shock and can cause serious injury or death.
Under normal circumstances, the electrician is powered off for maintenance and is not allowed to operate. However, for various reasons, there are often sudden calls at the inspection point. If the disconnected main power switch is mistakenly closed, the circuit breakers (such as automatic switches and contactors) that have no obvious breaking point are subjected to strong vibration and bouncing misclosing. If there is an accidental electrification at the inspection point, the electrician is likely to have an electric shock. Therefore, the electrician must strictly implement the safety work procedures for power failure maintenance during routine inspection and maintenance work to prevent electric shock.

1 Possible electric shock circuit

There are three types of electric shock circuits that electricians may cause during maintenance:
(1) Electric shock circuit between two wires: When the two different parts of the human body of the repairer touch the exposed parts of the two wires at the same time, or two terminals, the human body connects the circuit between the two wires to form an electric shock circuit. If the two phase lines of the low-voltage line are touched, the human body is subjected to a line voltage of 380V; if the human body touches a phase line and a neutral line, the human body is subjected to a phase voltage of 220V.
(2) Electric shock circuit between the ground and the ground: When the human body of the repairer touches a charged phase line and conductive ground, wall column, water pipe, etc., the current will flow through the human body, the building and the earth to form a loop. The human body may also be subjected to a voltage of 220V, and the current flowing through the human body is also a serious threat to life.
(3) The electric shock circuit of the human intervention circuit: When the electrician is inspecting the single-wire control switch (such as ordinary electric wire switch), fuse or wire connection point, if the human body touches two terminal terminals or two wire ends at the same time, once When the circuit is powered, the human body is strung into the loop. At this time, the current through the human body is related to the power of the electrical appliance, and often exceeds the extent that the human body can withstand.

2 Avoid safe operation techniques for the formation of electric shock circuits

In order to prevent the formation of the above three types of electric shock circuits, the electrician must strictly implement the following three safety operation principles when performing low-voltage electrification maintenance work:
(1) Single-line operation: During maintenance work, the human body cannot touch two wire ends, or two terminal blocks, or two contacts at any time. It must be processed with one wire end and one wire end. Adjacent bare conductors that may be touched by carelessness must be pre-shielded.
(2) Isolation from the earth: When the electrician is inspecting, all parts of the human body must be reliably insulated from the earth (including conductive buildings and pipes that are connected to the earth). Therefore, electricians must wear electrical insulation shoes, protective overalls, and tools with insulated handles, as well as dry ladders with bamboo or wood structures, in strict accordance with safe work practices. If it is not equal, it can be placed underneath with insulation such as dry wood. At the same time, the human body cannot touch the building during operation. In addition, when accepting tools or parts that are not isolated from the ground, the repairer must stop the operation and the hands must be removed from the inspection point. In this way, it is possible to avoid the formation of an electric shock circuit between the lines.
(3) Breaking the current loop: When the electrician is inspecting the individual circuits of the electrical appliances, the closed loop that the circuit may form should be eliminated first. For example, when repairing the light switch, the bulb must be removed first, so that even if the human body touches the two terminals of the switch at the same time, it will not form a closed loop due to human intervention. For example, when replacing the entire fuse on the power distribution board, the power plug of the mobile power tool must be removed first, so that even if both hands touch the upper and lower connection heads at the same time, a closed loop will not be formed due to human intervention. In addition, when repairing the lamp cap or hanging the wire box, the light switch must be disconnected, so as to avoid the electric shock circuit formed when the two terminals are touched at the same time (also belongs to the electric shock, when the human body replaces the electric appliance, the human body in the circuit It became a load).
It must be emphasized that: power outages should be done as much as possible, power should be checked before work, and sudden calls should be prevented. If there is no need to work with power, the above three safety measures to avoid the formation of various electric shocks must be used at the same time. If only one or two of them are used, an electric shock can still occur. For example, if the safety measures against the earth are not taken, even if the two measures of single-line operation and breaking circuit are strictly adopted, the electric shock circuit between the lines and the ground will be formed; if only measures to isolate the earth are taken, then the other two An electric shock circuit is also unavoidable. Therefore, the above three measures must be adopted at the same time to ensure the safe operation of the electrician.