Equipment grounding conductors and bonding: a vital link in electrical system protection

摘要

Electrical equipment grounding and bonding conductors must be sized to withstand the maximum fault currents imposed during abnormal system conditions. It is noted that many low-voltage distribution systems do not contain adequately sized equipment grounding conductors and bonding jumpers, compromising personnel and system safety. It is emphasized that proper consideration of conductor withstand ratings provides improved equipment grounding, system reliability, and safety. Examples are presented which illustrate the engineering and design issues associated with proper selection and sizing of the equipment grounding conductor and associated bonding conductors. Particular consideration is given to insulated conductor withstand ratings, bare conductor withstand ratings, and conductor sizing using a current-limiting device. It is concluded that it is the responsibility of the design engineer to comply with the National Electrical Code requirements as well as to understand the nuances of proper electrical protection associated with component and equipment withstandability.