Test cell for interfacial electric strength testing

Interfaces between solid insulating materials are critical in high voltage apparatus. In this work a test cell was designed for measuring tangential breakdown strength of an interface between insulating rubber and silicone gel. The test cell comprised two disc-shaped electrodes with a rubber cylinder pressed between them. The electrodes and the rubber cylinder were cast in silicone gel thus creating the rubber-gel interface. The test cell was used to measure breakdown voltage (AC) of rubber-gel interfaces on 19 samples. In 14 of the tested samples the breakdown occurred at the rubber-gel interface whereas in the remaining five samples the breakdown occurred in the bulk gel or inside the rubber cylinder.