In recent years

the accident ratio of circuit breaker explosion when a substation switches on/off10 k V shunt capacitors has been rising. Through the authors’ analysis

it is found that the similar explosion accidents are of universality and particularity and with apparent change of the bus system. This paper presented that the change of bus system will impact on the switching operation of 10 k V shunt capacitors. And the theoretical analysis and simulations of effect mechanism are made. The results proved that the capacitance to ground of bus and cable forms a capacitor charging and discharging circuit and the change of bus capacitance to ground produces a high frequency circuit component

and that if the switching operation is performed in this case the circuit of the circuit breaker between contacts will be with high frequency over zero and equivalent closure

and a high-frequency overvoltage of very high amplitude（4.5 p.u.） will be produced on the load side and across the break of the circuit breaker

which would be possible to cause the reignition of the circuit breaker and the insulation breakdown of the equipment such as the circuit breaker and the shunt capacitor.