Laboratory and field experiences with EHV transmission line insulators in the desert

The paper deals with different aspects of insulator contamination in the desert, based on extensive laboratory tests and field experience with 500 kV transmission line insulators. It is shown that the build-up of the contamination layer in the desert is a gradual and slow process. Light sand particles are shown to be the major contamination source. A special technique is described to investigate the interaction between the contamination layer and atmospheric humidity. Flashover tests with natural and artificial contamination proved the necessity of detailed evaluation of dispersion and stressed the role played by the inert binder of the contaminant. Statistical methods for predicting insulator performance are presented and several factors of practical significance to line insulator selection in the desert are analyzed.