Structuring Dielectric Interfaces for Enhanced Electrical Strength

The energy transition towards a carbon-free economy requires an increased expansion of the electrical grid. Applications such as joints, bushing and terminations with electrical potential separation are limited in their electrical strength caused by discharges. Especially in cable accessories involving medium to extra-high voltage applications, where the surface roughness and assembly inaccuracies lead to cavities between the insulation parts are critical for electrical strength. These cavities, if above a certain size, initiate discharges and trigger damage processes of the insulating material at the interface. Controlled surface structuring of silicone insulation material in the micron range based on a wrinkle-formation process introduces a controlled cavity volume between the insulation parts, which reduces the number of failure-trigged cavities and extends the interface length simultaneously. Discharge measurements show a clear tendency towards higher breakdown (BD) voltages for reduced wrinkle-controlled cavity sizes with BD values of 45.9 kV compared to 26.5 kV for an undefined microstructured (rough) and 38.0 kV for a triangular structured silicone. The resulting compressed cavity size was analyzed and used for electric field simulations, which shows the dependency between the structure feature and the field magnitudes. The partial discharge inception voltage (PDIV) measurements indicated a lower voltage for triangular structures compared to wrinkle-controlled structures reflecting the severity of the ionization process.