scope:

Foreword

This guide was prepared by the Working Group on the Neutral Grounding of Distribution Systems of the IEEE Surge- Protective Devices Committee. The guide deals with the neutral grounding of single- and three-phase ac utility primary distribution systems with nominal voltages of 2.4 kV through 34.5 kV. Not included are grounding of low-voltage secondary systems or consumer-owned facilities that are covered by other standards.

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.

Scope

This section of the guide is concerned with the neutral grounding of single- and three-phase alternating current (ac) electric utility primary distribution systems with nominal voltages in the range of 2.4 kV to 34.5 kV. For the purpose of this guide, the term "distribution" includes the substation providing power to distribution feeders, the distribution feeders, and the distribution transformers providing service at utilization voltages. The scope of this guide does not include the grounding of the low-voltage secondary systems supplied by distribution transformers, or consumer-owned facilities that are covered by other standards such as the National Electrical Code (NEC) [B6].