New diagnosis method of unknown phase-shifted PD signals for gas insulated switchgears

In many cases of on-site PD measurement, it is difficult to acquire the perfect phase angle of the PD signal synchronized with the applied voltage. This paper describes a new method of PD diagnosis which can classify the types of defects for unknown phase-shifted PDs using decision tree method. 327 cases of on-site PD data were collected in the field. 5 valid parameters were extracted and the decision tree-based diagnostic algorithm was used to classify types of 6 PDs and 4 noises clearly. Finally we confirmed the new method of PD diagnosis can be applied to on-site GIS diagnosis.