Improvement in the pollution performance of standard suspension-type disc insulators by the use of semiconducting inserts

A computational study was carried out in order to verify the assumption of reducing the magnitudes of electrical stresses generated in standard suspension-type disc insulators energized with high voltage alternating current (HVAC), by including a semiconducting insert within their geometry. As a consequence, an improved performance of these insulators was expected during flashover tests in polluted conditions. Grading of stresses in the region adjacent to the pin of insulators is the factor responsible for such improved performance. These computational and experimental results were compared to those obtained from similar calculations and tests, but considering conventional non-modified insulators. Two different conductivity characteristics of the semiconducting insert were considered during the simulations. Then, an electrical evaluation of the above referred alternatives, as well as an additional set of alternatives was also developed in a clean fog chamber. Results from computational studies showed decreases in the maximum stress found in the test arrangement ranging from 29% up to 45%, with respect to those corresponding to the base case (conventional insulators). These values are in a reasonably good agreement with increases achieved in the flashover voltage of the corresponding alternatives, when evaluated in the clean fog chamber. Increases in the flashover voltage resulted 33% and 44% for each simulated case, respectively. For every alternative evaluated, an increase in the corresponding flashover voltage was always achieved. In the worst case, a 12% increase was obtained; for the best case, an increase even higher than 97% was found.