Efficient PD Monitoring of HV Electrical Systems Using HFCT Sensors

The evaluation of the insulation condition of high voltage (HV) electrical grids by means of non-invasive and on-line partial discharge (PD) monitoring is currently a common practice in the maintenance programs of electrical utilities. Several difficulties must be undertaken when on-line temporary measuring or monitoring applications are applied, the most important are: high levels of background noise and the appearance of interferences, the simultaneous presence of different PD sources, the requirement of locating the insulation defects emplacement and the challenge of identifying them. An on-line PD electromagnetic method that implements non-invasive high-frequency current transformers (HFCT) as sensors for PD temporary measuring or monitoring is explained in this article. The application of the proposed method and the use of powerful signal processing tools enable the performance of accurate diagnosis with regard to the insulation condition of HV electrical installations. The signal acquisition of the HFCT sensors used is synchronized to discriminate whether an eventual PD source detected is located in a certain element of the HV installation. The effectiveness of the measuring or monitoring method and of the signal processing tools proposed is demonstrated through experimental measurements, where PD type pulses were measured simultaneously in a HV installation configured in a laboratory setup.