Influence of load on operating conditions of third harmonic ground-fault protection system of unit connected generators

The influence of the load of the unit connected generator on the operating conditions of the ground-fault protection of the stator windings of the generator, excited by the ratio of the third harmonic voltage in the generator neutral and at the generator terminals to ground, was analysed. On the basis of the theoretical analysis, experimental tests and computer simulations, relations between the voltage feeding the measuring element of the ground-fault protection and the load of the unit during ground faults along the entire length of the stator windings were determined. The influence of the method of balancing ground-fault protection on the third harmonic voltage feeding its measuring element was determined. It has been found that correct operation of the ground-fault protection calls for the the influence of the load on the resolution of the third harmonic voltages in unit connected generator circuits to be taken into account