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某天,在化学水处理室进行电气安装施工的电工,突然发现所有的电动工具都带电“麻手”,手枪电钻、电焊机、台式电钻等无人敢用。根据情况分析,电动设备在同一时刻同时损坏的可能性不大,很可能故障出现在电源部分。因为这些电动设备的外壳都进行了保护接零,只有零线上有了对地电压,才能使所有电动设备的外壳带电。可是零线上的对地电压又不可能存在,因为某一相线碰零线时,就形成该相线对零线的单相短路,短路电流使线路上的保护装置迅速动作,从而把故障部分与电源断开,消除触电危险。但电气工地上使用的专用电源箱里的熔断器及自动开关并没有动作。
One day, an electrician who performs an electrical installation in a chemical water treatment room suddenly discovers that all electric tools are charged, such as “hemp”, pistol electric drills, electric welding machines, bench drills, and others. According to the situation analysis, electric equipment at the same time damage is unlikely at the same time, it is possible failure in the power section. Because the housing of these electrical equipment is protected to zero, only the voltage on the zero line to earth, in order to make all the electric equipment shell live. However, zero voltage on the ground and impossible, because a phase line touch zero line, the formation of the phase line to the zero line of the single-phase short-circuit current to the line protection device moves quickly, so that the fault Part of the disconnect from the power supply to eliminate the risk of electric shock. However, the fuses and automatic switches in the dedicated power box used on the electrical site did not operate.