Modeling flashover of AC outdoor insulators under contaminated conditions with dry band formation and arcing
IEEE transactions on dielectrics and electrical insulation
A power system can be well designed to withstand expected lightning and switching surge voltages with proper insulation coordination. However, when the insulator surface is covered by a pollution layer, flashover could happen at lower voltages. This has been a well known weakness of outdoor insulators [1, 2] . Various national and international standards organizations have developed standards to evaluate this aspect in the laboratory . The tests are fairly elaborate and incur significant
... r and cost. Good theoretical models for calculating the flashover voltage will enhance the value of the experiments and permit transmission line engineers to make reasonable predictions over a wide range of operating conditions and for insulators incorporating different shapes and materials. This report presents a theoretical model for evaluating the performance of insulators in terms of pollution severity at which flashover occurs for different system voltages and various insulator configurations and material types. The model introduces several new features such as, the formation of dry bands along the insulator surface and variations in surface wettability. The model draws heavily from experimental measurements of flashover voltage and surface resistance measured under varying wet conditions of insulators with housings made from silicone rubber, ethylene, propylene rubber and epoxy, as well as electric field distributions obtained from software for 3-dimensional models. It has been demonstrated that it is possible to change the insulator shapes without changing the leakage distance and realize significant improvement in flashover performance. The predictions have been validated with experimental results. ii To my parents Song Bai and Peiqin Xue for their endless love and support iii ACKNOWLEDGMENTS I would like to express my sincere gratitude to my advisor Professor Ravi Gorur, whose expertise, understanding, and patience, added considerably to my graduate experience. He not only taught me about research, but also helped me to improve my writing, thinking and communication skills. He provided me with direction and support in the areas not only restricted to research but also in life and career, and became more of a mentor and friend. Special thanks towards Professor Richard Farmer and Professor Vijay Vittal, whose kindness, care and encouragement have supported me continuously during my years at Arizona State University, which truly made a difference in my life. I appreciate a lot for their time and consideration in being on my supervisory committee. It is great honor to have them.