I have a design application with 480/277V double-ended (main-tie-main), 2000A cont. switchgear and with a backup emergency generator. Currently, I have included GFP on all circuit breakers - mains, tie, and feeder breakers for the 480/277V Switchgear. Switching is completed through the switchgear circuit breakers rather than a ATS. The switchgear has redundant generator circuit breakers. Which means the switchgear has (2) circuit breakers, one on each side of the split bus leading to the emergency generator. My question is concerning ground fault protection. If the scenairo came up that both utility service feeders leading to 480/277V switchgear had failed (lost power) and generator was the only prime mover, should GFP be enabled on the circuit breakers? My thought is that GFP could pickup and nuissance trip if not set properly. This systems feeds airport lighting on the airfield and is a critical system because people's lives are on the line. The NEC does not state much on airport systems. I have been looking at Health Care Facilities NEC guidelines figuring this may be a good start and a conservative approach. NEC 517-17, prohibits the installation of GFP between on-site generator(s) and any EES transfer switch feeding EES switch feeding EES Circuits. This tells me that there should not be GFP. Is there another place that would cover my application? Is this the right way (Health Care Facilites) to look at this application?