Technical aspects of interfacial phenomena in solid insulating systems

HV insulation systems are often composed of different insulating materials. In the contact areas between these materials (interfaces) interfacing polarization may occur, resulting in an increase of both permittivity and loss tangent and, consequently, of dielectric losses. By the interaction of humidity such interfacial phenomena may be enhanced. Other important characteristics of insulating systems such as the treeing strength and the breakdown strength are also lowered by interfaces, especially when humidity has been adsorbed. Microscopic and macroscopic, internal and external interfaces are defined for composite insulation systems. Interfacial phenomena in such systems, for instance made out of fiber glass-reinforced polymeric materials, are described both under dry conditions and in the presence of water. It is demonstrated that the hydrophobic properties of materials improve the dielectric characteristics; this is true for bulk and surface properties