Investigating practical experiments of partial discharge localization in transformers using winding modeling

One of the well-known methods of partial discharge (PD) localization in transformers is based on winding modeling. Although the method is theoretically precise, the reliability of the method is not known in practice, because of the difficulties that arise in high frequency modeling of the winding. In this paper, to investigate the reliability of the PD localization method in practical cases, different types of PD including PD in air, PD in paper voids, PD in oil gaps and surface PD along insulator are produced. A 20 kV/0.4 kV research transformer with 6 accessible clamps along its winding and a specially prepared 63 kV winding with 30 accessible clamps are used as test objects. The generated PD pulses are injected to different clamps of the test objects and recorded at both ends of the windings by means of a wideband modern PD measuring system. A modified method based on using multi conductor transmission line model (MTLM) of transformer winding is used as PD localization method and to increase the reliability of the results, a method based on using calibration pulses is proposed. At last, the accuracy of PD localization results in the two test objects is investigated.