Core Balance Current Transformer

We're here to help

Talk to an expert today.
Our friendly team of highly trained specialists will quickly assist you.

Get a quote technical support +61 (0) 2 8045 5185


The CBCT also known as a zero sequence CT is used for earth leakage and earth fault protection. In the CBCT, the three-core cable of three single cores of three phase systems passes through the inner diameter of the CT. When the system is fault free, no current flows in the secondary of the CBCT. When there is an earth fault, the residual current (zero phase sequence current) of the system flows through the secondary of the CBCT and this operates the relay. In order to design the CBCT, the inner diameter of the CT, the relay type, the relay setting and the primary operating current needs to be stated.

Core balance current transformers are intended for providing a very sensitive method of earth leakage protection on three-phase electrical systems with suitable relays.

Cables of all phases pass through the inner diameter of the transformer and there is no output under no-fault conditions. In the event of an earth-fault a non-zero current exist and induces a changing magnetic field within the core, which in turn generates a secondary voltage which operates a relay (via burden).

We can optimally custom-design to your specific requirements based on relay types and settings, and the required primary operating current.

Feel free to give us a call or email us with your specific requirements and we will be happy to custom build this CT for you.

Customisable Parameters:

  • Primary rated current
  • Relay type
  • Relay setting
  • Burden
  • Maximum System Voltage
  • Frequency
  • Inner diameter of the CT