For insulators, quality and moulding is important. The relatively low viscosity of RTV/LSR-Silicone Rubber systems requires significantly lower injection pressure in comparison to HTV. For simple parts, “gravity” moulding is applicable.

The high viscosity of the preferred HTV-Silicone Rubber system requires high pressure injection moulding. The typical range of pressure is 1,500 bar and above. The process of injection moulding enables efficient bulk volume production but, however, sophisticated processing and corresponding tools are required due to the combination of high pressure and high temperature. Moulding can be made in one or multiple steps; multiple steps optionally offer a discontinued mould line along the insulator.
Owing to the fact that the lack of filler results in a combination of an axial mould line and lower erosion performance, PFISTERER SEFAG does not recommend this Silicone Rubber system for critical pollution and the transmission voltage level.

The higher the applied voltage, the more non-uniform (nonlinear) the voltage distribution along the insulator becomes. The risk for partial discharges in the mA-range, which burn stable across dry bands, increases and might require a correspondingly high erosion resistance.

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