Electrical characterization of fused silica-reinforced liquid silicone rubber for high voltage outdoor bushing applications

Abstract

Neat liquid silicone rubber is also used as a hydrophobic flexible outdoor high-voltage insulation․ Due to its lower dielectric strength and mechanical stiffness‚ however‚ LSR is not suitable for all bushings and outdoor insulation applications requiring very high reliability over long periods․ To overcome this drawback‚ fused silica-reinforced LSR composites containing 0 to 25 wt% of silica were fabricated․ The dielectric‚ surface‚ arc-resistance‚ mechanical‚ morphological and structural properties of the composites were evaluated․ It was found that the incorporation of fused silica remarkably improved the insulation performance of LSR compositions․ The breakdown strength increased from 18 kV/mm for the neat LSR to 38 kV/mm for the 25 wt% fused silica․ The dielectric constant increased from 3․5 to 4․6․ The decay of surface potential became slower with increased filler content‚ due to an improved charge retention by the deeper charge trapping sites․ In terms of arc resistance‚ an increase from 90 s to 224 s was observed‚ indicating a better resistance to surface tracking and carbonization․ Other improvements include an increase in Shore A hardness from 48 A to 64 A‚ as well as an increase in the tensile strength from 3․2 MPa to 8 MPa․ Its hydrophobic character‚ displayed in contact angles of greater than 90° was confirmed‚ reaching up to 107․6° at 20 wt% fused silica․ SEM and XRD results proved that fillers were well dispersed among the matrix and the composites were amorphous․ FS- LSR composites improved dielectric strength and mechanical strength‚ and showed promise for outdoor applications in high voltage insulation devices‚ such as bushings‚ surge arresters‚ insulator housings and seals.