Erosion Suppression of Zinc Borate Filler in HTV Silicone Rubber under AC Dry-Band Arcing

This paper investigates the erosion suppression mechanisms of Zinc Borate in high-temperature vulcanized silicone rubber using the IEC 60587 inclined plane test and simultaneous thermogravimetric-differential thermal analysis. Alumina tri-hydrate is employed in this study as a reference filler for comparison with Zinc Borate filler. The dehydration of Zinc Borate is reported to start around 350°C, whereas alumina tri-hydrate starts dehydration at lower temperatures around 230°C. An insignificant difference is shown in the erosion resistance between the alumina tri-hydrate and Zinc Borate-filled composites. Both fillers are shown viable in preventing the tracking and erosion failure in the IEC 60587 inclined plane test under the critical 4.5kV AC_rms voltage. Zinc Borate is found to suppress failure with the formation of residue acting as a shield against the progression of erosion. Whereas, alumina tri-hydrate alleviates surface temperature by promoting an internal oxidation mechanism that suppresses combustion of silicone rubber. This study's findings highlight the potential application of Zinc Borate as a cost-effective filler in high-temperature vulcanized silicone rubber for outdoor insulation, particularly in regions where this filler is readily available.