Leakage Current Measurement in LDPE under DC Polarity Reversal Stress

Insulation material performance is severely impacted by the HVDC polarity reversal (PR), and life estimation models demonstrate that LDPE under short reversal time interval failed quickly as compared to higher intervals. This difference in breakdown time is explored in relation with LDPE leakage current characteristics. The experiments were performed in a 30μm sample under 200 kV/mm electric field of 1 minute and 10 minute reversal. An ammeter hardware setup is used to measure the current until breakdown. The continuously measured current of each reversal interval was sequentially split into three sections and compared. Significant difference in instantaneous polarization and relaxation current was observed. Also, dissimilar leakage current trend in 1 minute and 10 minute tests was observed, and these results were correlated with the charge dynamics in LDPE to explain the variations in the breakdown.