The influence of digital measurement system characteristics on PD patterns

Digital systems to measure PDs have been widely adopted in the last years. Therefore the need of simple and effective methods to elaborate the large amount of available data, relevant to PD activity, arises. For example, it has already been shown that parameters resulting from statistical analysis of PD patterns can allow one to determine the nature of PD sites. Nevertheless the significance of the statistical parameters can be strongly affected by the measurement system characteristics and, in particular, by its adjustments. In the paper it is shown how the characteristics of the measurement system (amplifier gains, acquisition time lag, number of channels) can affect the PD patterns and relevant statistical parameters. For this purpose, two different experimental set-ups have been adopted, measuring PDs which act on the surface of polymeric films or inside tree channels. In this way, the acquired PDs were also relevant to different degradation levels of the PD site