Effects of Corona on Plastic Laminates

Corona arc, as a source of many undesirable effects, is a constant problem to designers of electrical equipment. In many cases the designer has been able to eliminate corona. Where complete elimination of corona has not been feasible, the problem becomes a search for an engineering material whose performance is not influenced by corona. It is this phase of corona study, dealing specifically with the performance of engineering materials in a corona arc, which is the subject of this paper. Corona attacks both metallic and non-metallic components by physical, chemical, and thermal action. Its attack on the insulation components presents one of the more important factors influencing the service life of electrical machines and equipment. The modern trends toward miniaturization in electrical circuits, reduced sizes of equipment, and decreased spacing of parts have tended to increase the occurrence of corona. Hence, there has developed a considerable interest concerning information on the corona-resistance properties of insulating materials. The investigation conducted by the Naval Material Laboratory, New York Naval Shipyard, has been confined to various types of plastic laminates. It was the aim of this study to determine the resistance of these materials to corona attack, as might be indicated by changes in certain of the electrical and mechanical properties after extended periods of exposure.