Compatibility Study of Silicone Rubber with Capacitor Impregnation Fluid

The leakage of insulating fluid has always been a problem for liquid-impregnated capacitors that is partly attributed to the compatibility issues. In the present study, a systematic compatibility test between gasket material of silicone rubber and impregnation fluid of mono/di-benzyl toluene (M/DBT) was carried out. By varying the test duration time and extending the examinations both on liquid and solid material, the interaction between impregnation fluid and gasket material was found to be the swelling of silicone rubber together with the precipitating of additives from rubber to M/DBT, which led to the deterioration of electrical properties of liquid material and mechanical properties of solid material. Consequently, an optimization of compatibility test method was proposed that it was necessary to prolong the test duration time with for at least four weeks and to evaluate both the insulating liquid and gasket material.