Dielectric failure of volume and surface types

IN THIS investigation, an attempt is made to obtain an interpretation of phenomena and also to serve practical ends. Since laboratory tests are preferably simple and of a controlled nature, the results are very limited when weighed against the multitudinous considerations of field applications. After earlier exploration, in which both materials and techniques were given careful scrutiny, four solid dielectrics were chosen for the present study.1¿3 Failure of practical dielectric structures in most cases is clearly through a volume of solid or else across the surface at an interface. Therefore, values of electric stress necessary to produce puncture constitute many of the compiled data in this paper. Likewise, flashover voltage is given for the materials as determined from the use of a fixed structure in air. The frequency range was from 60 cycles per second (cps) to 100 megacycles per second (mc), and the effects of temperature and humidity were studied.