Standard underground electrical equipment is designed to withstand the mechanical forces generated by bolted faults on the load terminals until a power circuit breaker or other protective device can interrupt the flow of fault current. This capability is verified by short-circuit and short time withstand tests on the equipment and interruption tests on the power circuit breakers. During a bolted fault, the voltage at the fault location is essentially zero and the fault energy is dissipated throughout the power system. The arc generated within the power circuit breaker during interruption is cooled and extinguished by the breaker. The minimal out-gassing of arc by products is contained in the electrical equipment as verified by interruption tests.

Arc Temperatures Exceed 35,000°F
Becker Global America’s arc resistant electrical equipment provides and added degrees of protection above standard MSHA requirements. In addition to bolted faults, Becker’s arc resistant electrical equipment is designed and performance tested to ANDI/IEEE C37.20.7 to provide protection from the hazards of internal arcing faults. An internal arcing fault can be caused by insulation degradation, insulation contamination, entrance of water, foreign objects coming into contact with the energized bus or any other unplanned condition that creates an electrical discharge path through air. During and arcing fault, the voltage at the fault location is essentially the system voltage and the fault energy is focused within the equipment, Arc temperatures can exceed 35,000 degrees rapidly heating the air, vaporizing metal parts and creating thousands of pounds of impact force. The expanding plasma creates severe mechanical and thermal stress in the equipment, which can blow off top covers and panels open doors and burn through the enclosure.