When measuring the high current of alternating current, it is necessary to convert the secondary instrument to a more uniform current (the secondary rating of the current transformer is 5A or 1A in China) , in addition, the voltage on the line are very high, such as direct measurement is very dangerous. Current transformer will play a role in converter and electrical isolation. 

It is a sensor for measuring instruments, relay protection and other secondary equipment in power system to obtain current information of electrical primary circuit. Current transformer converts high current into low current in proportion, and the primary side of current transformer is connected to the primary system, secondary side connection measuring instrument, relay protection, etc. .