A Study on Long-Term Characteristic of Local Electric Field in XLPE Cables

Abstract

In this study, we evaluated deterioration characteristics of XLPE insulation under higher electric field than threshold level using block model samples with needle-plane electrode and also XLPE cable model samples with simulated defect. We conducted long-term aging test more than 50000 hours and life exponent “n=18” was obtained from the constant life exponent of V-t characteristics (inverse power's law (V-n=t)) of XLPE block samples, and “16.8” was obtained from the constant life exponent of V-t characteristics of XLPE cable samples. Even when the defects existed, it was confirmed that the deterioration characteristics showed the life exponent to be close to the conventional design value of “n”=15. We confirmed that with regard to the oxidative ageing behavior, the electric field dependency was observed in the defect by needle electrode, in which higher electric field shows higher ageing especially. It is suggested that the deterioration characteristics is gradually influenced by oxidative ageing with time and accelerated by related electric field.