Ground Fault Protection in Frequency-Selective Grounded Systems Fed by a Single Transformer

This paper presents experimental results for performance tests of ground fault protection schemes applied to a frequency-selective grounded system supplied by a single transformer. Frequency selective grounding systems are designed to present low ground impedance (similar to solid grounding) to high frequency zero-sequence current components and impedance like that of a low-impedance grounded system to fundamental zero-sequence components. The variable impedance of the grounding scheme can impact the response of ground fault protection in terms of accuracy and timing. The laboratory setup includes a single 35kVa 3-phase source transformer with a 340/208-volt secondary voltage. Experimental results detailed in this paper demonstrate the response that may be expected of various types of GFP schemes under fault and non-fault events and conditions.