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

This paper presents performance assessment of ground fault protection for systems supplied by a transformer, which has frequency-selective grounding. Frequency-selective grounding is a new grounding system that is designed to act as a solid-grounding for high frequency currents, and as a low resistance-grounding for low frequency currents. This grounding system is composed from a parallel $R-C$ circuit with an equivalent impedance able to affect system zero-sequence currents and ground potentials. Such effects on zero-sequence currents and ground potentials can directly impact the accuracy and response speed of ground fault protection. Effects of frequency-selective grounding on ground fault protection are experimentally assessed for different fault and non-fault events, when the transformer supplies linear and non-liner loads. Experimental results demonstrate responses of various implementations of ground fault protection to fault and non-fault events, when the protected system has frequency selective grounding. Moreover, presented results and discussions aim to demonstrate the ability of frequency-selective grounding to support the operation of ground fault protection during different loading conditions and fault events.