High-resistance neutral grounding in industrial systems and the ground fault protection

The objective of this paper is to present the state-of-the art in the high-resistance neutral grounding practice in LV (480V) and MV (4.16kV) industrial power systems, not still widely known in Brazil, especially regarding the ground fault detection and location systems, and equipment protection with selectivity. This technique is important for the quality of energy and continuity of service in industrial processes. It is also presented a new synthesis for the range of adjustment of the ground-fault protection relays based on the constraints of the first ground-fault coexistence in the power supply system, the ground protection selectivity in the case of a second fault, the effective ground protection of equipment, and on the avoidance of nuisance tripping due to the charging current flow during faults. The possibility of using high-resistance neutral systems up to 4.16kV and beyond is discussed based on today´s assumption of the limits of a self-sustainable carbonous arc in motor winding insulation failures and the calculation of charging currents.