The improved voltage life characteristics of EHV XLPE cables

Although many researchers have investigated voltage life characteristics of XLPE cables, the voltage life curve of XLPE insulation has not been made c lear because of large deviations in the obtained data. Moreover, the voltag e life curve of a XLPE cable, which is significantly affected by defect siz e and shape, can not be applied to another cable having different defects. The authors obtained an intrinsic stress life curve of XLPE which included no defects. The intrinsic stress life curve demonstrates the existence of a threshold stress, which causes no degradation in the insulation. The appli cation of the intrinsic stress life curve makes possible to estimate the vo ltage life curve of any cable with known defects. A method for calculating the defect size that would not initiate any degradation in XLPE insulation under a given electrical stress is proposed.