by David L. Swindler

Low-voltage power distribution systems are typically grounded by one of two generally accepted methods, high-resistance grounded systems (a derivative of the ungrounded system) and solidly-grounded systems. High-resistance grounded systems have gained in popularity due to the fact that the first line-to-ground fault does not cause a disruption of service and is favored for continuous processes or critical loads. For power systems that cannot be monitored by qualified maintenance personnel, or for other reasons, the solidlygrounded system still has widespread use. A four-wire solidly grounded system can become very complex, involving many sources, points of grounding, and networks of distributed power. This paper discusses a method of providing equipment ground-fault protection to seemingly impossible systems. Index terms — Ground-fault protection, low-voltage power systems, power system protection.