Explain working of ELCB with neat sketch diagram.
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Earth Leakage Circuit Breaker(ELCB): Earth leakage circuit breaker is a safety device used in electrical installations with high earth impedance to prevent shocks and disconnect power under earth fault conditions. It works on principle of relaying when the current in the earth path exceeds a set value. ELCB is used for protection against electric leakage in the circuit of 50 Hz or 60 Hz, rated voltage single phase. 240 V, 3-ph. 440V. Rated current up to 60 Amp. When the earth fault occurs, the ELCB cuts off the power within the time of 0.1 sec. automatically to protect personnel.

Under normal conditions (IL – IN) = If is very low or nearly zero. The CT surrounding the phase and neutral senses the differential current under earth fault and actuates the CB to operate (open). The difference current If through fault path resistance Re is the leakage to earth. If this value exceeds a preset value, then the CB opens. Normally it is around 35 mA for tripping in domestic installations with tripping time being as low as 25 msec.

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