Development of a Novel Method For Continuous Neutral Grounding Resistor Monitoring

Neutral resistance grounding has been utilized to make power systems safer for more than 70 years. There are conditions where a resistively grounded power system can become unsafe, and those instances can be discovered through continuous monitoring of the NGR resistance value and parasitic loss impedance. Upon measuring a hazardous condition, the power system can be de-energized. Continuous monitoring devices have been developed and deployed but have shortcomings when measuring the value of the neutral grounding resistor and non-fundamental frequency ground-fault currents. The authors describe a novel monitoring system to accurately measure the resistance value of the neutral grounding resistor (NGR), the impedance of parasitic losses between the neutralizing point and protective-earth, evaluate non-fundamental frequency ground-fault current, and reduce nuisance tripping. The elements of the proposed device are discussed and analyzed in detail. Results from testing components of the proposed method are provided and discussed.