On-line PD detection in power cables using matched filters

Abstract

On-line measuring of partial discharge (PD) is generally impeded by noise, and in many cases PDs cannot be detected without filtering. Solely the pulse propagation path and the response of the detection circuit determine the shape of a PD pulse; therefore a PD can be regarded as a deterministic signal embedded in additive noise. The optimal filter for this class of signals is the matched filter, which maximises the signal-to-noise ratio at the filter output. Matched filters allow making reliable observations of PD signals embedded in noise and precise estimations of signal parameters, such as arrival time and charge. In order to obtain PD matched filters; knowledge of the PD wave shapes is crucial. A cable propagation model provides such knowledge, and matched filters can be designed specifically for the cable under test. Moreover, by estimating noise statistics the matched filters can be tailored for a practical measuring situation. Experimental results show that partial discharge detection greatly benefits from matched filtering