The current transformer TZLU-100-1 operates according to the following principle: it is connected to a three-phase cable with a diameter of up to 100 mm. The cable passes through the transformer window. A zero magnetic field is formed around it due to the same angle of displacement of all phases during normal operation.
This compensates for the emerging fields. And when any cable cores are shorted, the compensating force disappears, which leads to the appearance of a voltage in the transformer under the influence of zero-sequence currents. This voltage is transmitted to the relay, which triggers the protection. It is also used to transmit signals to control, signaling and automatic devices. It is installed indoors or under a canopy. It is used in areas with a temperate climate (climatic design "U").