Grounding and ground fault protection considerations specific to emergency/standby generator sets

Abstract

Careful consideration of the grounding arrangements of AC generators used in emergency and standby power systems is essential for optimum continuity of power for critical loads and for the safety of personnel. There are grounding and ground fault protection considerations that are specific to emergency/standby generators when interconnected to a commercial AC power source through transfer switch equipment or when paralleled to another power source. Specific considerations for emergency and standby systems include selection of a system grounding method for the generator, when and when not to use four-pole transfer switch equipment, requirements for indication only of a ground fault on the generator, and the use of simultaneously switched neutral or overlapping the switched neutral.<>