scope:

This publication is a guide of practical information containing instructions for the safe and proper application of ground fault protective devices (hereafter referred to as GFP devices).

GFP devices include current sensing devices (GFS), relaying equipment (GFR), combinations of GFS and GFR equipment, or other equivalent protective equipment that will operate to cause a disconnecting means to open all ungrounded conductors at predetermined values of ground fault current and time. GFP devices are intended to protect equipment only against extensive damage from ground faults.

GFP devices are intended to operate circuit breakers or fusible switches equipped with electrically actuated tripping means. These devices may be supplied as an integral portion of the disconnecting means or as separate devices operating in conjunction with the disconnecting means.GFP devices may or may not require external control power for proper tripping operation.

GFP devices are designed to be used primarily on solidly grounded distribution systems rated up to a maximum of 600 volts ac to provide for rapid clearing of ground faults. The National Electrical Code® (NEC) requires ground fault protection in certain instances. In other situations, ground fault protection is added at the request of the customer. This application guide does not cover all possible applications of these devices.

GFP systems described in this publication are intended for equipment protection only. They cannot provide protection for personnel. A GFR system designed for protecting equipment cannot protect personnel against electric shock hazards because personnel protective devices, such as ground-fault circuit-interrupters, require a sensitivity in the low milliampere range. The systems used to meet the requirements of Article 230-Services and Article 517-Health Care Facilities of the NEC have a sensitivity in the multi-ampere range. This application guide does not contain information on ground fault protection for personnel (GFCI).