Electrothermal Characterization of HVIC Under Bipolar DC in Concurrent Extended Stressing and Dry Band Arcing

Room temperature vulcanized silicone rubber (RTV-SiR) is broadly recommended as a high-voltage insulator coating (HVIC) for ceramic insulators in polluted zones. However, the rising high-voltage direct current (HVdc) ranges impose serious challenges in terms of coating degradation. To increase the acceptability of HVIC, the present work investigates the electrothermal characteristics of RTV-SiR for HVIC using the inclined plane test in conjunction with long-term accelerated aging. Four types of RTV-SiR composites are fabricated by adding various wt% of micro, nano, and micro-nano (hybrid) silica fillers. Inclined plane tests (IPT) are conducted separately for both polarities of dc on pristine and aged samples (treated with accelerated multistressing in the lab for 10 000 h). Unaged hybrid samples (SB4) outperform by achieving the highest initial tracking voltage (ITV) of 3.25 kV for negative polarity dc (-dc) IPT, followed by the counterpart under positive polarity dc (+dc). Similarly, a notable suppression of leakage currents (LCs) is witnessed in hybrid and 20 wt% silica-added composites throughout the IPT campaign. Also, from time to failure analysis, a relatively shortened time to failure is observed for all blends treated under positive dc, confirming the detrimental impact of positive polarity. For instance, unaged pure SiR samples (SB1) feature 6 h before failure under-dc stress compared to 5 h when +dc is applied. From the findings, it is recognizable that hybrid composites depict better overall performance, followed by samples with 20 wt% filler, thus showing high integrity under all test conditions.