Behavior of Elastic Syntactic Foams under Impulse Voltage Stress

Elastic syntactic foam is a special kind of composite material. It consists of a silicone gel matrix (called binder) and hollow spherical particles with a diameter in the range of 20 - 200 mu m (so called microspheres) which are mixed into the binder. This Material is very soft, elastic and features a high compressibility as well as a strong adhesion to other solids. In the field of insulation systems, it is already used to substitute mineral oil in cable terminations. For the dimensioning of insulation systems, it is necessary to have a precise knowledge about the phenomena occurring during a breakdown process. The breakdown mechanisms of syntactic foam under AC and DC stress was introduced in earlier papers. New applications in medium and high voltage systems also require knowledge about the behavior of elastic syntactic foams exposed to impulse voltage stress. In order to characterize the microspheres' influence on the electrical properties of the material, the lightning impulse voltage dielectric strength of elastic syntactic foams which are made of different polymeric microspheres (different diameters, different filling degrees) are determined and compared. Further tests deal with influence of temperature on the dielectric strength under impulse voltage. In combination with theoretical investigations and field simulations, the results of the experimental investigations are used to develop a model of the breakdown mechanism of elastic syntactic foam exposed to impulse voltage.