Evaluation of a New Protective Coating for Porcelain Insulators
This paper describes the evaluation of a new elastomeric coating made from a silicone rubber compound for use on porcelain insulators. Field experience has shown that coated insulators have a lower flashover probability under wet contaminated operation than uncoated insulators.
Electric Field Grading Using Thin Film Nonohmic Zinc Oxide
The transient response of thin film non Ohmic zinc oxide is studied to determine if the material would be able to keep up with power system abnormalities such as switching surges and lightning strokes. The transient model is based on a lumped parameter model of the distributed problem. It is found that the maximum electric field seen by the insulator was a function of film thickness, ground capacitance, and the characteristic time of the drive. It does not appear to be affected strongly by the internal capacitance of the film. The switching time of the film, being on the order of a nanosecond, does not appear to have an effect on transients of the time scale of lightning or line switching, indicating satisfactory film performance for sufficient thicknesses.
Control of insulator contamination in substations
Abstract This paper discusses in detail the procedures used by the Florida Power & Light Company which have resulted in 6 years of virtually “flashover proof” substations. The successful prevention of flashovers due to contamination in its 69, 138 and 240 kV substations and switching stations is described.