Electrical Field-Strength Dependent Space Charge and Charge Decay Characteristics at Silicone Rubber / Silicone Grease Interfaces

Abstract

Dielectric interfaces as the silicone grease / silicone elastomer interface in DC-cable accessories pose great challenges in the design due to possible accumulation of space charges. This paper evaluates this silicone grease / silicone elastomer interface under DC-influence in respect to its space charge behavior in dependence on field strengths. It is shown that at lower field strengths only charges of one polarity prevail at the interface while at higher field strengths charges of opposite polarity evolve. Furthermore, it was found that with rising field strengths, charge moves from the interface to the enclosing electrodes leading to a decreasing overall amount of charge at the interface. By analyzing the time dependent charge decay it was shown that decay constants significantly differ at the interface and at the enclosing electrodes.