This circuit breaker is a indoor high voltage switchgear with three-phase AC 50Hz and rated voltage 40.5 kV, which is suitable for all kinds of load and frequent operation. It can be used for the control and protection of electrical facilities in industrial and mining enterprises, power plants and substations. The product performance meets the requirements of GB1984-2003 “High Voltage AC Circuit Breaker” and IEC 62271-100:2001 “High Voltage AC Circuit Breaker”, which reaches the domestic advanced level.