Advanced PD site location in distribution power cables

Advanced on-site PD analysis is often used for insulation condition assessment of power cables to enable predictive maintenance. Most advanced PD analysis techniques are based on time domain reflectometry applied to time resolved PD pulse sequences detected on-site on either one or multiple cable-endings. Performing PD on-site analysis of power cables may provide large sets of measurement data. Nevertheless, due to the on-site conditions it may sometimes be very difficult to extract the necessary information. By applying dedicated numerical post-processing of the measuring data, the essential information such as the magnitude, the inception voltages, PD patterns and discharge site location can be obtained. In this paper a number of useful techniques is applied to provide as much as possible information for condition assessment purposes. In particular, the wavelet transform is used for separation of noise and disturbances from time-domain PD signals. A data base protocol has been proposed to use in the decision support of condition assessment. A practical example of numerical post-processing using wavelet de-noising on PD data obtained from field measurements is shown.