The main reason of frequent operating overvoltage in breaking 35 kV shunt capacitor is the chopping current and multiple reignition of the vacuum circuit breaker during the breaking period. For avoiding the occurrence of such fault the mechanism of chopping current

reignition and simultaneously breaking overvoltage of three phases is analyzed

the electromagnetic transient model for breaking 35 kV shunt reactor is set up by the use of ATP-EMTP. It is shown by the simulation result that the lightning arrester only limit overvoltage amplitude

cannot change oscillation frequency of the overvoltage. The RC-absorber not only can change the high frequency oscillation circuit and reduce the steepness of wave front and the oscillation frequency of the overvoltage

but also can suppress the chopping current and multiple reignition of vacuum circuit breakers. At present

the protection scheme of installing 3-phase star-connected arrester on the 35 kV busbar and the shunt reactor side has no way to limit effectively overvoltage between phases

while the threephase combination arrester can do and the RC absorber is much better. For the 220 kV substation

it is recommended to install three-phase combined arrester on 35 kV busbar side of the substation and to install either three-phase combined arrester or RC absorber on the shunt reactor side.