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Considerations for the application of a MV high speed grounding switch for arc flash mitigation of LV equipment

This paper expands on the work of a previous paper that presented the possibility of a significant reduction of incident energy on the secondary of medium voltage to low voltage (MV-LV) transformers with the combination of a high speed grounding switch (HSGS) and traditional MV current limiting (CL) E-Rated fuses. It was shown that when the HSGS is applied at a location between the E-rated fuse load terminals and the transformer's primary connection and controlled by relays on the LV side, incident energy can be reduced to less than 1.0 cal/cm2. Whereas the first paper focused on the results from a high power test lab, this paper discusses issues related to its application on typical power systems and lessons learned from installations at several locations. Application considerations include a review of relay requirements, coordination of E-Rated fuses, requirements for resistance grounded systems, modeling in analysis software and field installation considerations.