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Reply To: Protection Question No.14 – Earth fault relay setting

#1384
Hamid

    Ground-fault protection of medium-voltage and high-voltage systems has been applied successfully for years using ground current relays (device 51G). Ground-fault protection of low-voltage systems is a considerable problem because of the presence and nature of low-level arcing ground faults. Leakage ground-fault current is low magnitude current (milliampere range) generally associated with portable tools and appliances. Leakage ground-fault current presents a hazard to personnel. Personnel protection from leakage ground-fault current is provided by ground-fault circuit interrupters and are required by the NFPA 70 in certain locations. Arcing and bolted ground-fault currents are higher magnitude currents, and are associated with equipment damage rather than personnel hazard. That doesn