Mechanical locking is a locking mode in which the mechanical structure of the operating mechanism of switchgear restricts each other, thus achieving mutual interlocking. Electromagnetic locking is to use the auxiliary contacts of circuit breakers, disconnectors, circuit breaker doors, etc. to turn on or off the power supply of electromagnetic locks such as disconnectors and switch cabinet doors that need to be locked, so that their operating mechanisms cannot act, thus realizing the mutual locking between switching devices. The locking device is simple in principle and convenient to realize, and locking can be realized between different switchgear; It works well in a dry environment. However, due to our "national conditions", most of them are installed on indoor equipment of 35 kV and below. In use, due to various reasons, the auxiliary transfer switch can not be switched normally, and the electromagnetic lock can not meet the sealing requirements and is corroded by moisture, so that the locking often fails. For outdoor high-voltage switchgear, electrical logic locking is mostly used to prevent false locking.