Ground-Fault Protection of Electrical Systems with Emergency or Standby Power

Providing reliable ground-fault protection in electrical systems having alternate emergency or standby power can present serious problems unless adequate equipment is selected and properly coordinated. Multiple neutral-to-ground connections may prevent adequate sensing of ground-fault currents and may also cause nuisance tripping of circuit breakers. This paper discusses various approaches that have been proposed to solve these problems. Particular emphasis is placed on code requirements and overall reliability of the electrical systems.