NONSTATIONARY BEHAVIOR OF PARTIAL DISCHARGES IN A GENERATOR STATOR CONDUCTOR DUE TO VOLTAGE CONDITIONING EFFECTS

Often partial discharge measurements on generators are taken immediate ly after the application of a test voltage. From measurements on a ful l-sized bitumen-mica generator conductor, it was observed that partial discharges go through a transient phase immediately after the applica tion of a voltage or after the voltage has been changed. Parameter val ues derived during this time are therefore subject to variations and d o not adequately reflect the true static condition of the insulation. After the transient phase, however, partial discharges behave in a sta tistically stable manner and repeatable measurements can be obtained e ven for long durations. The paper describes the long-duration measurem ent method used to observe the partial discharges and discusses releva nt to computerised measurements. A vector representation of the partia l discharge data and analytical methods are described that may be used to screen nonstationary data in an automated partial discharge data a cquisition environment.