A transformer ​is a device that converts voltage or current proportionally. The function of the transformer is to convert high voltage or high current into standard low voltage (100V) or standard low current (5A or 1A, both referring to the rated value), so as to achieve the standardization and miniaturization of measuring instruments, protection equipment and automatic control equipment.

When we open the power distribution cabinet, we can see that there are many current transformers in it. Some power distribution cabinets have only one, and some even have five or six. In fact, they all induce current signals from the bus, but the measured currents have different effects. So what role do they all play in the power distribution cabinet?

The wiring of the current transformer should follow the series principle: that is, the primary winding should be connected in series with the circuit under test, while the secondary winding should be connected in series with all instrument loads.