Electro-Optical Diagnostics of Single Partial Discharges

Light emission and electrical signals of partial discharge (PD) events in artificially introduced defects in insulating medium, namely polyethylene, polyvinyl chloride (PVC), silicone and polydimethylsiloxane (PDMS) have been examined. Internal discharges in a micro void and external discharges on insulator surface have been created using two specific experimental setups, which allow for observation of single discharges. The light pulses from single discharge events were registered by a photomultiplier. The discharge images have been acquired by an iCCD cameras with single and double stage amplification. Electrical signals have been measured using wideband probes. Two model arrangements have been developed and applied. Results of optical measurements are compared with conventional phase resolved partial discharge (PRPD) patterns. There exist different correlation modes between light intensity and value of partial discharge current, which can be ascribed to different type of PD origins. The comparison of optical and electrical signals shows a good correlation between both detection methods. Analysis of obtained discharge patterns in dependence on used material and electrode polarity is presented. It is shown that optical signals obtained from proper diagnostic devices carry similar information as conventional PRPD diagrams. The results of investigations can be used for development of new PD diagnostics.