On-line partial discharge detection in cables

This paper describes an on-line partial discharge (PD) detection technique in power cables. The technique uses a digital spectrum analyzer with a high-frequency preamplifier and several types of high-frequency inductive sensors. In extruded and impregnated cables, the PD detection is made in the VHF range. The suitability and the sensitivity of the VHF technique were checked against two other conventional PD detecting methods (Pulse Phase Analyzer and Fast Digital Scope) by performing PD measurements in EPR-insulated cable under laboratory-controlled conditions. The suitability and sensitivity of the VHF method were as good as the two conventional PD detection method. The VHF method runs used to conduct on-site PD measurement in several power cables. These measurements were conducted while the cables were in service. Special care was given to distinguish between external electromagnetic noise and electromagnetic signals produced by the PD activities inside the cable insulation