This recommended practice covers the system grounding of industrial and commercial power systems. The basic reasons for grounding or not grounding the electrical system and the various types of system grounding@ as well as the practices commonly used to ground electrical systems are discussed. Purpose Grounding of an electrical system is a decision that must be faced by engineers charged with planning or modifying electrical distribution. Grounding in some form is generally recommended@ although there are certain exceptions. Several methods and criteria exist for system grounding; each has its own purpose. It is the intention of this recommended practice to assist the engineer in making decisions by presenting basic reasons for grounding or not grounding and by reviewing general practices and methods of system grounding. The practices set forth herein are primarily applicable to industrial@ institutional and/or commercial power systems that distribute and utilize power at medium or low voltage@ usually within a smaller geographical area than is covered by a utility. Where distances or power levels may dictate circuitry and equipment similar to a utility@ consideration of utility practices is warranted. In addition to the general technical considerations in the practice of grounding as discussed in this Recommended Practice@ pertinent codes or standards imposed by local regulatory authorities@ the particular needs of service@ and the experience and training of the workforce should also be considered. Where an industrial or commercial power system includes power-generating equipment@ the reasons for grounding these components may be the same as those for grounding similar components of public utility systems. The methods of grounding would generally be similar under like conditions of service. However@ in the industrial or commercial setting@ conditions of service may be altered by the following: (1) Location within the power system (2) Individual generator characteristics (3) Manufacturing process requirements (4) Emergency/life safety requirements of the local codes The standards listed in section 2@ Normative references@ are considered minimum requirements for the protection of life and property and should be carefully reviewed during the course of system design. The recommended practices in this document are intended to supplement@ and not negate@ any of the requirements in the NEC@ IEC or any other location specific regulatory codes. Therecommended practices in this document are intended to provide explanations of how electrical systems operate. A better understanding of the electrical principles will assist the engineer in implementing the recommendations in a manner that best provides for the needs of a specific design function.