Study on the Method of Diagnosing the Live-Wire Insulation of High-Voltage XLPE Cables by DC Superimposition

Abstract

Recently, as part of preventive maintenance for equipment, there have been greatly increasing needs to diagnose the insulation of cables under hot-line conduction. In a background, there is a large number of equipment which was constructed around the high-growth period in the 1965s and have become obsolete, in addition to recent circumstances which make it difficult to obtain longer service interruption time.
In this paper, therefore, the results of study on the method measuring the live-wire insulation resistance by superimposing DC 50 V to a high-voltage busbar through GPT and forming a bridge with the resistane of a cable insulation taken as a side, are discussed. It was clarified that this live-wire insulation diagnostic method can detect the degradation of a cable insulation resistance from the high level and is therefore suitable for so-called trend monitoring as well.