Insulation deterioration diagnosis on ultra high voltage power cables

Tests were performed for an insulation deterioration diagnosis on ultra high voltage power cables from the generator to the main transformer at the Daecheong hydroelectric power plant. These cables have been in service for over 22 years. With this mind, an investigation concerning the present conditions and the securing of basic data toward a life span diagnosis was conducted over 3 months, beginning in April of last year. In this diagnosis, we conducted the following tests: insulating voltage measurement, D.C. leakage current measurement, recovery voltage measurement, tan δ measurement and partial discharge. According to our findings, for power cables from both generator 1 and 2, there was only a slight possibility of equipment failure or defect and this only during the recovery voltage measurement testing. At present it´s not severe, but follow-up checks will be needed again in 3 or 4 years.