Performance Testing of the Ratio Ground Relay on a Four-Wire Distribution Feeder

Digital fault investigations on six Pennsylvania Power and Light (PPL) 12 kV distribution feeders led to the development of a prototype ratio ground relay to theoretically provide better detection of broken conductor faults. Further assessment of the relay´s performance was provided through analog computer tests followed by staged fault testing on an operating distribution feeder. Performance tests are described and documented. These positive test results provided the incentive to monitor the performance of the ratio ground relay on several PPL distribution feeders.