Interposing types can be used to modify the secondary current from an existing line CT. This is useful for modifying secondary currents without replacing the line CTs.
The main function of an interposing CT is to balance the currents supplied to the relay where there would otherwise be an imbalance due to the ratios of the main CTs. Interposing CTs are equipped with a wide range of taps that can be selected by the user to achieve the balance required.
As the name suggests, an interposing CT is installed between the secondary winding of the main CT and the relay. They can be used on the primary side or secondary side of the power transformer being protected, or both. Interposing CTs also provide a convenient method of establishing a delta connection for the elimination of zero sequence currents where this is necessary.
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.