Testing of high voltage cable lines by damped ac technique — A case study

In this paper, a case-study is presented, which emphasizes the role of local degradation detection besides the general condition assessment of the high voltage cable line insulation. The applied damped AC method provides several diagnostic parameters e.g. PD inception and extinction voltages, PD map and loss factor therefore it is an effective tool in cable diagnosis. The partial discharge tests detected the weak points of the investigated cable line, which were mounted with porcelain terminations. After the replacement of the terminations the cable line has become PD free. This case study emphasizes that from the point of view of reliability, the weakest points of the HV cable lines are the cable accessories. The time of the failure of these components cannot be predicted exactly, the only way to prevent the failure is the regular diagnostic testing of critical cable lines.