Explain with simple diagram the core balance CT.

Explain with simple diagram the core balance CT.
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In core balance CT all the three phases go through the core and the resultant magnetic flux is zero. Because the flux of three phases cancel each other. So the secondary output of CT is zero and the relay will not energise. When there is a earth fault in one of the phase the fluxes cannot balance each other and there is a voltage induced in secondary of the CT and the relay is energised to trip the circuit. Saturation is no problem because the core size is very big.

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