Rigid polyester foams for electrical application: characterization and measurements

The introduction of polymeric foams in electrical applications such as components for HV and MV systems is envisaged as possible under the following conditions: the polymeric foams have to be surrounded by an integral skin; and the foam density has to be chosen in the light of a compromise between partial discharge inception voltage and breakdown voltage. In order to improve the characterization of the foamed insulating systems, it is deemed necessary: to study foams with voids filled by insulating gases (e.g. SF/sub 6/); to optimize the integral skin and the type of resin; to continue the electrical characterization by investigating the medium and long term behaviour in the presence of stresses; to evaluate the behaviour under impulse voltages of the insulating components; and to develop 'ad hoc' designs to build components noticeably different from the ones used in the case of 'solid' insulated systems.<>