Partial Discharge Diagnosis of Generator Insulation Systems - Measurements, Simulations and Picture Recognition

PD patterns indicate faults in the mica insulation of the stator windings of high voltage synchronous turbo generators. The common used method for PD measurement on electrical machines is the phase resolved partial discharge pattern (PRPDP) Method. Usually these patterns can only be interpreted by experienced test engineers. A computer program has been developed which is capable of interpreting these PD pattern in a qualitative manner. The presented diagnostic routine is focused on insulation faults of turbo generators which are classified according to an international standard. For system verification several generators with different age, from different manufacturers where investigated. Both measurement results under regular operation condition (online diagnosis) and diagnoses with external power supply (offline diagnosis) were evaluated. Additionally simulations models for the discharge processes have been developed. A network-type model simulates discharges in voids of different geometry. The parameters are calculated with a finite element model of a discharge process in an insulator void.