Correlation between Partial Discharge Inception Voltage and Breakdown Voltage Characteristics of Butt-gap in HVDC Mass Impregnated PPLP Cable

The voids are formed inside the butt-gap in the HVDC Mass Impregnated PPLP (MI PPLP) cable since the thermal contraction of the mass is about ten times larger than PPLP. When the DC voltage applied to the MI PPLP cable is above partial discharge inception voltage (PDIV), partial discharge occurs in the void. The continued partial discharge accelerates electrical ageing and breakdown may occur as a result. Hence, it is necessary to study the correlation between partial discharge inception and breakdown in DC steady state. Partial discharge and breakdown in the DC steady state are affected by the temperature and the polarity of the applied voltage. Therefore, in this paper, to analyze the correlation between PDIV and Breakdown Voltage (BDV) of butt-gap in HVDC MI PPLP cable, BDV and PDIV measurement were performed according to temperatures of the specimen and polarities of the applied voltage. From the experimental results, The BDV of the butt-gap in the MI PPLP was found to be inversely proportional to the conductivity and proportional to PDIV. Also, PDIV and BDV were higher at negative voltage compared to positive polarity voltage. Consequently, BDV can be predicted through the temperature of the MI-PPLP and PDIV.