Design of Booster Sheds by Laboratory Experiments for Icing Protection of EHV Post Insulators

摘要

Adequate electrical insulation and improvement of flashover performance of HV insulators are demanding issues for utilities in cold climate regions. Based on field experience, more than fifty percent of the icing flashover problems in North America are related to station insulators. Therefore, this paper concentrates chiefly on the icing problems of station post insulators. In order to solve problems of the electrical performance of post insulators in heavy icing and snow conditions, they could always be replaced by new types of insulators. However, this solution is not only expensive but it may not be effective enough to solve the problem. In the last decades, several methods have been proposed to improve the electrical performance of insulators in that concern. Among these approaches, an effective one is using insulator accessories like booster sheds (BSs). A booster shed (BS) is a c-shaped device usually made of high quality flexible insulating materials such as ethylene vinyl acetate (EVA) and silicone rubber. The main objective of this paper is to describe an experimental test procedure for optimizing the design of BSs under heavy icing conditions. Classification and calculation of BS parameters (i.e. number, diameter, inclination angle, and position) as well as the final experimental validation tests are explained. In general, the proper formulation of a problem takes about 50% of the total effort required for obtaining a final optimized design. Hence, it is significant to follow a precise method for formulating an optimization problem. Based on IEEE standard 1783, the maximum withstand voltages (V_(WS)) are used for ranking the electrical performance of different BS configurations. After the proper formulation of the project, proposing a solution in a creative process could be quite complicated. PVC sheets were found to be acceptable to fabricate BS prototypes for research purposes under extra high voltage and heavy icing conditions. The final experimental tests demonstrated the effectiveness of the optimized BS configuration in improving the electrical performance of the post insulators. More particularly, the tests determined the V_(WS) of an EHV standard post insulator equipped with 6 BSs under severe ice conditions (30-mm on a monitoring rotating cylinder). The experimental results were in good agreement with our previous simulation analyses.