Abstract: Abstract: This paper studies and analyzes the principle and operating conditions of the disconnector in the electrical locking circuit of the disconnector in 500kVXX substation. The locking circuit of the disconnector is an important part of the secondary circuit of the substation. Mastering its circuit is an effective means to ensure that the staff will not have malignant electrical misoperation. This paper uses the deductive method to simulate the operation of the disconnector locking circuit, verify the correct operation process and analyze its functions. The staff must be familiar with the principle of the electrical locking circuit of the disconnector, so as to correctly realize the switching operation and abnormal handling, prevent the occurrence of misoperation, and protect the stable operation of the power grid.