The study of the effect in variation of A.C. applied voltage to the partial discharge localization inside transformer windings

Ageing processes typically associated with the dielectric and insulation system occur inside high voltage plant. These unwanted processes may lead to generation of partial discharge (PD) activity and ultimately limit the operational life of the plant. The operational over stressing and defects introduced during manufacture also lead to the existence of PD activity and the source of this activity needs to be identified and remedied before further degradation processes cause catastrophic failure. Therefore, research into localization techniques of PD sources inside high voltage plant generally and particularly within transformer windings has become important in order to provide the asset health information that allows maintenance and replacement processes to be carried out effectively. Locating a PD source inside a transformer winding using on-line measurement data is vital in order to achieve these objectives. Methods have been proposed to achieve this and in this paper the distribution of PD signal energy in the time and frequency domains is used as a location tool. Analysis of experimental data reveals that this approach is independent of the applied voltage.