Locating partial discharge sources in high voltage transformer windings

The analysis of partial discharge (PD) measurement data obtained using radio frequency current transducers (RFCT) incorporated into the external earthing connections (i.e bushing tap points and neutral to earth connections) offers the possibility of on-line condition monitoring of large transformers. A method for locating PD sources in windings has been developed, based on analysis of differential equations that model the propagation of PD signals from the source to the measurement point. Analysis reveals that if the discharge at the source is assumed to be impulse-like, then the form of the response at the measurement points can be simulated as a function of source location along the winding. If all parameters of the winding are known then it is possible to model the response, however, in the field this is often not the case. So the method developed here uses information from the PD measurements themselves to estimate the unknown coefficients required to simulate the likely discharge currents. With these estimates it is then possible to compare PD measurement information with simulation data in order to identify the most likely location of a PD source. An experiment based on a section of high voltage winding has been used to produce PD measurement data and to validate the proposed approach.