CTX Series zero-sequence current transformers are used in conjunction with relay protection devices or signals when the power system generates zero-sequence grounding current, so that the device components can operate to achieve protection or monitoring.

When an electric shock or leakage fault occurs in the circuit, the secondary side of the transformer outputs a zero-sequence current, ensuring the connected secondary line equipment will trigger protection protocols (power cut-off, alarm, etc.).

The working principle of a zero sequence current transformer (ZCT) is based on the concept of magnetic induction. It measures the unbalanced current in a three-phase electrical system, also known as neutral current.

When an unbalanced current flows through the primary winding (connected to the neutral conductor), it creates a magnetic field that induces a proportional voltage in the secondary winding. This induced voltage allows instruments or relays to detect ground faults and protect the system from damage.