It may not be always possible to detect high resistance faults by convectional earth fault relaying. In such cases a very sensitive current relay will be required for this purpose. It can be connected residually since it has an adjustable definite time delay provided to take care of transient spills in the residual circuit due to CT mismatch. Also, its low burden enables it to be used with existing CT's/ Relays without affecting the performance.; The incoming current is stepped down by an internal current transformer and converted to a voltage by a variable resistor network. The signal is compared with an internal reference. When this reference level is exceeded, a time delay is initiated, after the time delay has elapsed, a relay operates.