Dynamic Fault Testing of Ground Sensing Relays

Performance testing of a ground fault protection system has traditionally been accomplished by simulating high level fault magnitudes at current transformer secondary. For a new chemical manufacturing facility, a procedure was devised to safely stage ground faults on the 480-V distribution system. To implement the procedure, a test set was developed that placed a controlled ground fault on the system and measured current magnitude and tripping time. Tests were conducted without the need to modify the distribution system or the ground protection wiring in any way. This feature revealed discrepancies that would not have been discovered following more conventional test methods.