IEEE Guide for the Application of Neutral Grounding in Electrical Utility Systems, Part IV-Distribution

The neutral grounding of single- and three-phase ac electric utility primary distribution systems with nominal voltages in the range of 2.4--34.5 kV is addressed. Classes of distribution systems grounding are defined. Basic considerations in distribution system grounding--concerning economics, control of temporary overvoltages, control of ground-fault currents, and ground relaying--are addressed. Also considered are use of grounding transformers, grounding of high-voltage neutral of wye/delta distribution transformers, and interconnection of primary and secondary neutrals of distribution transformers.