Optical detection of partial discharges in gas-insulated systems

In gas-insulated systems (GIS) defects such as free metallic particles, protrusions from the electrodes and defects associated with insulators can lead to partial discharges (PD) and, ultimately, to electrical breakdown. Of the various diagnostic techniques used in monitoring GIS, electrical and acoustical methods of PD detection are most commonly employed. However, the conventional methods of PD detection are often hampered by electromagnetic noise which may prevent detection of certain types of defects. In this respect optical method of PD detection offers advantages, especially when new, less ambient temperature-operated mini photomultiplier tubes are used. This paper describes optical measurements of partial discharges in a scaled-down model of GIS under ac, dc and impulse voltage conditions and compares their sensitivity with the sensitivity of conventional electrical PD measurements