Breakdown Testing of Pressure- and Cure-bonded Silicone Rubber Interfaces

Dielectric interfaces are critical in determining the reliability of high voltage insulation systems. By considering new experimental results and data from electrical treeing in the literature it is shown that not only is the nature of the interface being studied important, but so is the electrode configuration. In particular, voids around the electrodes are critical to inception and development of a track. Unlike in electrical treeing tests where homogeneity is often sought in a laboratory sample, it is concluded that understanding the nature of the interface being modelled is essential and that experimentation must replicate service materials and systems. Comparison of silicone rubber interfaces formed purely by pressure and those which are bonded must be differentiated by whether the source of partial discharges (here a needle tip) is vented, and whether a void is present at the point of discharge initiation.