Influence of voltage transformers on operating conditions of ground-fault protection system for unit-connected generator

The influence of voltage transformers on the operating conditions of the ground-fault protection systems of unit-connected generators excited by the ratio of 3rd harmonic voltages in the generator neutral and at the generator terminals was determined An optimising analysis of these conditions with regard to the value of the voltage transformers feeding the protection system was carried out. Simulation tests were run for high-power unit-connected generators equipped with generator breakers with capacitance to ground It was found that the optimisation of the voltage transformers ratio markedly improves the operating conditions of the protection and ensures 100% protection of the length of the starer winding. (C) 1998 Elsevier Science Ltd. All rights reserved.