Mechanism of Overvoltage Induced by Fast Switching On-off 10 kV Shunt Capacitors Using Vacuum Circuit Breakers

Accidents grow frequently in 10 kV power systems in recent years when using vacuum breaker to switch shunt capacitors. Preliminary statistics indicates nearly 50% of these accidents occurred with operation of fast switching on-off. Hence after defining this specific operation of breaker firstly, we theoretically derived the mechanism of overvoltage generation in the operation and proposed some ideas including reconfiguration of transient circuit and fluctuation of bus-ground capacitance. Then we calculated this overvoltage using ATP-EMTP. Some patterns of the overvoltage are obtained from the calculations: the operation of fast switching on-off shunt capacitors will induce high overvoltage on load side of circuit breaker; the reconfiguration of oscillating circuit induced by ground capacitance impacts the transient process of operation greatly; with an operation overvoltage up to per unit value of 8.5, an operating breaker would be probably reignited or even broken down.