Long-term reliability testing of 500 kV DC PPLP-insulated oil-filled cableand accessories

This paper describes the results of a long-term reliability test of a newly developed 500 kV DC oil-filled cable and accessories that transmit up to 2 800MW. This is the largest capacity ever used for submarine cables. The tes t line was 500m and consist of submarine cables, land cables, and several k inds of accessories. An optical fiber sensor was first installed in the oil duct of the cable to measure the conductor temperature directly under appl ication of DC voltage. From 1994 to 1996, we carried out an accelerated ele ctrical and thermal aging test equivalent to 40 years, a load cycle test, a polarity reversal test and a transient overloading current test. Satisfact ory breakdown strength was confirmed in the residual test which followed th e long-term test. These results have been instrumental to the decision to c onstruct 500 kV DC commercial submarine cable lines.