Abstract :
Investigations of a number of generator stator-insulation failures have shown that breakdowns of several machines generating at 33 kV were initiated by discharge erosion of the insulation. The paper describes a method of measuring discharges in stator insulation. The technique consists in counting the number of discharge pulses exceeding a certain level. It is concluded that this proposed instrument has several advantages over other types of discharge detector. It is shown that, at the present time, this method, or indeed any other means of measuring discharges, cannot determine the depth of discharge erosion in generator stator insulation. In a complete stator winding, the internal discharges tend to be concealed by slot discharges, which may or may not be harmful, depending on the surface conductivity of the dielectric.
