DIAGNOSIS METHOD FOR LIVE-WIRE INSULATION OF HIGH-VOLTAGE XLPE CABLES BY DC SUPERIMPOSITION

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.