Diagnosis method for live‐wire insulation of high‐voltage XLPE cables by DC superimposition

Abstract

Recent preventive maintenance for equipment has grown to include diagnosis of the insulation of cables under hot‐line conduction. Much of the equipment constructed during the high‐growth period in the 1960s has become obsolete. Recent circumstances make it difficult to obtain a longer service interruption time. Results of a study of the method that measures the live‐wire insulation resistance by superimposing dc 50 V to a high‐voltage busbar through GPT and forms a bridge with the resistance of a cable insulation are discussed. It is clarified that this live‐wire insulation diagnostic method is highly effective at detecting degradation of a cable insulation resistance and is, therefore, suitable for so‐called trend monitoring as well.