In order to study the seismic performance of 252 kV porcelain circuit breaker under AG5

the reason for porcelain circuit breaker easy to be broken during earthquake is analyzed.In AG5 conditions

seismic performance of typical 252 kV porcelain circuit breaker has been calculated.The results show that: the natural frequency is increased obviously without chassis

so reasonable frequency could be designed to different geological conditions in order to reduce the damage from the earthquake to the circuit breaker;the highest stresses occurred in the root of the porcelain cylinder for with or without the chassis which exceeded the limit stress of the common porcelain.High strength porcelain insulator may be used in order to increase circuit breaker’s anti-seismic performance.But

in very high seismic level region

it is not recommended to use porcelain type circuit breaker

especially in electric railway substation.