Transfer function as tool for noise suppression and localization of partial discharges in transformers during on-site measurements

Partial discharge (PD) measurements are one the most important non destructive test methods to evaluate the integrity of the insulation system of power transformers. PD measurements on site are strongly influenced by noise and besides the level of the PD activity the location of the PD source is of importance. Using the well known transfer function from transformer impulse tests the variation of the PD signal travelling trough the transformer winding are the basis for the separation between noise and PD signals and also for the localization of the PD source. Laboratory tests show very good results. With a simple capacitive coupler and signal transmission via fibre optic cable the system can also be used satisfactorily on site.