电气系统的内部过电压触发的原因很多，既有线路参数匹配引起的工频过电压，也有开关操作时电弧复燃引起的操作过电压；此外还有电感负载负荷截流引起的过电压和电感电容串联引起的谐振过电压。内部过电压，特别是操作过电压引起的事故时有发生；据统计资料，一般工频过电压不会超过2倍相电压，切除空载线路引起的操作过电压和间歇性电弧引起的过电压不会超过3. 5倍相电压，铁磁谐振过电压不会超过3倍相电压。但是，实际运行经验证明，事故的发生往往是几种过电压叠加在一起， 过电压倍数有时高达额定相电压的7～8倍。 Electrical system of the internal overvoltage trigger for many reasons, both the circuit parameter matching of power frequency overvoltage caused by, also had an "on/off" switch operation arc operating overvoltage caused by again; In addition, there is a series of voltage and inductance voltages caused by the inductance load. Internal overvoltage, especially when operating overvoltage causes accidents. According to statistical data, the general power frequency overvoltage can't more than 2 times the phase voltage, remove empty lines caused by operating overvoltage and intermittent arc over-voltage caused by not more than 3. 5 times the phase voltage, phase voltage ferroresonance overvoltage can't more than 3 times. However, the actual experience shows that the occurrence of accidents is usually a combination of several voltages, which can be as high as 7 ~ 8 times as high as the rated phase voltage.