The secondary power equipment constitutes a system, not just the device itself, such as AC, DC, control circuits, etc. Due to the lack of monitoring methods for some circuits, real-time technical analysis and judgment of equipment status cannot be carried out. Therefore, in terms of the current application status of electrical secondary equipment, strictly speaking, most protections do not meet the conditions for condition based maintenance. The planned maintenance system adopted by power equipment in the power system has serious defects, such as frequent temporary maintenance, insufficient or excessive maintenance, blind maintenance, etc. This causes countries around the world to spend huge amounts of money on equipment maintenance every year.