The role of the current transformer In order to ensure the safe and economic operation of the power system, the operation of the power equipment must be monitored and measured. However, the general measurement and protection device cannot directly access the high-voltage equipment, but the large current of the primary system needs to be proportional. Transform into a small current and supply it to the measuring instrument and protection device.

The current transformer is used in an AC loop where the direction of the current changes over time. The polarity of the current transformer means that the polarity of the primary side is the same as the polarity of one end of the secondary side at a certain moment, that is, it is positive at the same time or negative at the same time, and the polarity is called the same polarity end or the same name end. The symbol "*", "-" or "." indicates. (It can also be understood as the direction relationship between primary current and secondary current).