Ground Fault Tests on High-Resistance Grounded 13.8-kV Electrical Distribution System of Modern Large Chemical Plant---II

Actual ground fault tests were conducted to determine the behavior of low-magnitude arcing ground faults in a closed air-filled 13.8-kV terminal chamber. Ground current magnitudes between 10 and 50 A were allowed to flow under various ground fault conditions. The tests that were performed support the value of high-resistance grounding to promote safety and reduce damage to equipment. At higher ground fault current levels the ionization of the air-filled chamber progresses at a rapid rate, and the arc is sustained or phase-to-phase faulting quickly occurs. The lower the ground fault current can be limited the less damage that occurs and the less possibility there is of creating a phase-to-phase fault. The practical consideration appears to be that if ground fault current can be limited to 10 A or less then initial ground faults will either clear themselves or create solid ground paths. This can allow the system to operate until an orderly shutdown procedure can be initiated.