Date of Award
Doctor of Engineering Science in Electrical Engineering
Raj Pratap Misra
R. E. McMillan
This study is a theoretical and experimental investigation on the state of the art of synthetic insulators for outdoor high voltage transmission systems.
The surface of a polymeric material is known to be degraded by, among other things, environmental stresses such as UV, air pollutants, etc. The reliability of an insulator material is governed by the surface and other characteristics that do not drift much as a function of stresses and time.
The surface characteristics of various synthetic materials, when these materials were exposed to UV radiation in the laboratory were studied. The changes in the surface properties of these materials were observed by measuring the electrical noise generated on the surface as a result of applied electric field, the hydrophilicity of the surface (θH2O) and the leakage current developed on application of electric stress before and after UV aging. UV aging decreases θH2O. The amount of change in the wettability of a particular specimen due to UV aging was related to the amount of change in the leakage current of the specimen and the amount of change in the surface noise generated on the specimen. Increase in hydrophilicity increases the surface noise and the leakage current, thereby degrading its effectiveness as an insulator.
Experiments were done to investigate the effects of exposing a typical polymer insulator made of R.B.G.F. core covered with silicone elastomer to polluting gases like NO2, SO2, H2S, and CL2, UV, and polluting gases plus UV. From the data obtained on the accelerated life tests, the life of the material in normal usage was extrapolated as a function of the above stresses using a modified Arrhenius equation. Suggestions are given for further research on the studies of insulator surfaces in new as well as degraded conditions.
Bhatia, Satyapal S., "Reliability and surface degradation aspects of synthetic insulator materials for HV application" (1977). Dissertations. 1317.