In 6-10kV civil building power supply system, the commonly used high voltage distribution equipment is high voltage circuit breaker, high voltage load switch, high voltage fuse, high voltage isolation switch, high voltage switchgear and so on. The purpose of high voltage circuit breaker: normal operation, put on or cut off the load circuit, in the short circuit fault, the use of relay protection device, can automatically and quickly cut off the overload or short circuit current, in order to prevent expanding the scope of the accident.

The working performance of the circuit breaker directly affects the safe operation of the power supply and distribution system. Therefore, it is required that the circuit breaker has a fairly perfect arc extinguishing device and a large enough arc extinguishing capacity. Its types are as follows:

Oil circuit breaker, using oil as the arc extinguishing medium is called oil circuit breaker. According to the circuit breaker oil amount and the role of oil and divided into more oil circuit breaker and less oil circuit breaker. Multi-oil circuit breaker oil has two functions, one is as an arc extinguishing medium; Second, it is used as an insulating medium between dynamic and static contacts when the circuit breaker is opened. The ground insulation is completed by air, sleeve and other insulating materials. Less oil circuit breaker is a kind of circuit breaker commonly used in China.