The Escalating Arcing Ground-Fault Phenomenon

The cause and avoidance of arcing fault burndowns of electrical equipments, particularly those operating in low-voltage solidly grounded systems, were well identified and documented in publications appearing in the 1960´s [1]-[5]. The subsequent occasional appearance of similarly devastating arcing ground fault burndowns in equipments operating on medium-voltage low-resistance grounded systems seemed to be irreconcilable with the presence of the relative high value of the neutral grounding resistor. A failure analysis based on on-site observations produced a probable scenario of escalating arcing ground faults, which explains the mechanism that will render the usual and proper complement of time-overcurrent ground-fault relays inoperative. A detailed description of the escalating arcing ground fault phenomenon is presented. It further identifies preventive arcing escalation solutions that impact on the specification of switchgear, switchboards, and motor control equipments.