Neutral Grounding Resistor:Various Fail-Safe Methods for Monitring of Healthiness

摘要

According to Regulation 100(1) of Central electricity Authority Regulations (Measures relating to safety and electric supply), 2010, the earth fault current in underground and open-cast mines, need to be restricted to 750 mA, and 50A respectively. This objective is achieved by introduction of NGR i.e. Neutral Grounding Resistor of appropriate specifications, between neutral of transformer or generator and earth. The monitoring of healthiness of NGR is of paramount importance, as any open-circuit of NGR, renders all the current operated earth fault relays defunct, for want of earth return path for the fault current.