Circuit breaker ， refers to the switching device that can turn on, carry and break the current under normal circuit conditions and can turn on, carry and break the current under abnormal circuit conditions within the specified time. Circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their scope of use. The division of high and low voltage boundaries is relatively vague, and generally, those above 3kV are referred to as high-voltage electrical appliances.