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

Actual ground faults were applied to a high-resistance grounded 13.8-kV electrical distribution system supplying power to a large chemical plant. These tests show that such a system will restrict overvoltage transients and reduce damage to equipment under ground fault conditions. Such a system is inherently safer and more reliable than an ungrounded system and offers some operating features not possible with a low-resistance grounded system. The maximum overvoltage transient recorded during many ground faults, involving several different ground conditions imposed on the system during six hours of testing, was about 2000 V. The effect of these ground faults on the 13.8-kV electrical distribution system supplying an operating plant was negligible. In fact, the operating personnel, anticipating the worst, were not aware that the tests had been performed.