Partial discharge location in power transformers
In a power transformer, high levels of partial discharge activity may lead to an insulation failure. If a partial discharge (PD) could be detected and located before the insulation fails, the transformer could be repaired or replaced before any consumers connected to the transformer lose supply. A technique is described in the paper that can be used to locate a PD in a power transformer with a continuous disc type winding. The technique requires knowledge about the physical geometry and design parameters of the transformer and also information about the characteristics of how the pulse or pulses caused by the PD propagate through the winding. The latter is difficult to obtain and consequently numerous simulation studies with slightly different assumptions were necessary before the technique could be considered validated. This involved analysing the data available at the terminals when a PD occurred in the winding and trying to extract the features related to the PD location. An algorithm using feature template matching has been used to locate the PD source in a 110 kV continuous disc type winding. Experimental tests carried out on this type of winding were extremely important in verifying the validity of the PD location algorithm. Results indicate that a location accuracy of better than 5% of the winding length is normally achieved.
