
NEMA Standards Publication PB 2.2-2004, Application Guide for Ground Fault Protective
Devices for Equipment provides guidance for the safe and proper use of ground fault protective
(GFP) devices. Its scope includes:
current sensing devices (GFS), relaying equipment (GFR), or combinations of current sensing
devices and relaying equipment, or other equivalent protective equipment which 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 only to protect equipment against
extensive damage from ground faults.
GFP devices are intende d to operate