Neutral ground resistor monitoring schemes

One distribution industrial/utility company in the Middle East has experienced several neutral ground resistor [NGR] failures during the past few years at its residential substations. These NGR's are installed in the neutral of the distribution power system transformers to limit the ground fault current. The failure of these NGR's caused the distribution system to be ungrounded. The existence of a phase to ground failure in the ungrounded power system leads to phase to ground voltage build-up in the other two healthy phases which can result in insulation breakdown and electrical equipment failures. This work is aimed at the development of two schemes and the evaluation of a third commercial existing scheme to detect NGR's failures.