Transformer bushing reliability

This TB explains bushing theory and types, the most prominent failure mechanisms and related mitigation measures. Questionnaires regarding bushing in-service failures and their relationship to transformer failure, bushing failures during transformer acceptance tests and regarding bushing diagnostics, maintenance and failure practice have been prepared, promoted, analysed and the results are presented. Bushing periodic and continuous diagnostic methods are explained in detail. For each method, traditional or recently developed, physical and measurement basics, condition decision criteria as well as effectiveness and limitations are provided. Several recommendations for bushing improvement are also given. Material will help to improve bushings and consequently power transformers reliability.