ELECTRIC FIELD AND VOLTAGE DISTRIBUTIONS ALONG NON-CERAMIC INSULATORS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Weiguo Que, M.S. * * * * The Ohio State University 2002 Dissertation Committee: Approved by Professor Stephen A. Sebo, Adviser Professor Donald G. Kasten Adviser Professor Longya Xu Department of Electrical Engineering UMI Number: 3081955 UMI UMI Microform 3081955 Copyright 2003 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road PC Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT High voltage insulators are essential for the reliable performance of electric power systems. All insulators, regardless of their material, are exposed to various electrical, mechanical and environmental stresses. The electrical stresses are the consequences of regular voltages and overvoltages. The mechanical stresses are related to the presence of various loads, e.g., the weight of conductors and hardware, wind load, ice load, etc. The environmental stresses of prime importance are the many forms of precipitation, UV radiation, and pollution. Since an increasing number of non-ceramic insulators are employed by electric utility companies for their new or updated power transmission lines, the analysis of their performance is relevant. The performance of these high voltage non-ceramic insulators is important for both dry and wet conditions. Long-term problems with them are related to the degradation of polymer materials used for the insulator, corona phenomena on the insulator surface, and pollution flashover. Most of these problems are related to the electric field distribution along the insulators. The dissertation research topic is the investigation of electric field and voltage distributions (EFVD) in the vicinity of non-ceramic insulators. A three-dimensional 11 electric field analysis software package, Coulomb, based on the boundary element method, has been obtained and employed for the calculations. Main contributions of the dissertation research to the state of the art are as follows: 1. Principles of the full and simplified models as well as the calculation models of dry and clean non-ceramic high voltage insulators have been developed for the purpose of accurate calculations together with efficient calculation times. The modeling and its procedures are illustrated in detail by practical examples. 2. Models of the high voltage insulators alone are not sufficient. The detailed modeling of several more major components have been found essential. These major components are the power line tower, the three phase conductors, all conductor hardware, and corona rings. The effects of all these components on the EFVD along dry and clean insulators are analyzed and discussed. 3. A simple model with a flat polymer insulating sheet between two electrodes and a water droplet on it has been used to simulate the behavior of a water droplet on the shed and on the sheath region, respectively, of a non-ceramic insulator. Basic studies related to the effects of the changes in water droplet contact angle, size of droplet, shape of droplet, distance between adjacent droplets, and conductivity of water have been described in terms of the electric field strength enhancement, always referred to an appropriate base case. Ill 4. Several models of a four-shed non-ceramic insulator exposed to rain or fog conditions have been initiated, following observations during and after aging tests in a high voltage fog chamber. The calculation models of nine examples have been developed. The electric field and voltage distribution along wet insulators have been calculated and analyzed. 5. Selected calculations on dry and clean insulators using Coulomb software package have been verified with an electric field strength meter. The correspondence of calculations and high voltage measurements has been reasonably good. 6. Several research issues applied to various practical insulator design aspects have been investigated and discussed, such as the effect of the distance between the first shed and the end fitting, the shed spacing, the shed profile and the position of the corona ring on the EFVD along polymer insulators. The research described in the dissertation is directly applicable to the field of high voltage insulator design and development. IV ACKNOWLEDGMENTS First and foremost, I express my sincere appreciation to Professor Stephen A. Sebo for guiding me through the most important five years in my life at The Ohio State University. I appreciate his invaluable guidance, insightful discussions, patience, and generous support throughout my studies. 1 would also like to thank Professors Donald G. Kasten and Longya Xu for their kindness of participating in my dissertation committee and for all their constructive advice. The generous support of Mr. Craig Armstrong, General Manager, Integrated Engineering Software was invaluable for this research. The use of Coulomb, an excellent software package of his company, Integrated, has made the dissertation research possible, as well as has made the completion time possible within a reasonable time. 1 also wish to thank Dr. Tiebin Zhao (The Ohio Brass Co.), who provided several polymer insulator samples used for this study. In addition, his technical advice and experience were indispensable for this research. 1 sincerely thank Mr. Robert Hill and Mr. David Crutcher (MacLean Power Systems) for their technical support by providing information and important examples related to 765 kV insulators and hardware. VI I am also grateful for the help of Mr. Ozkan Altay, my colleague, for spending his valuable time in order to conduct some of the experiments with me. My deepest love and gratitude go to my wife WANG Yue, who has shared the excitements and difficulties in my life with me. 1 am grateful for her deep love, her joy, invaluable support and encouragement throughout the last five years. 1 also owe special thanks to my parents, for the education and love I received from them, and for their full support over the years. VII VITA March 12, 1971 ..................................... Bom-Harbin, Heilongjiang, China 1994.......................................................B.S.E.E Tsinghua University, Beijing, China 1997 .......................................................M.S.E.E Tsinghua University, Beijing, China 1997 -2002 ........................................... Graduate Research Associate, Department of Electrical Engineering, The Ohio State University PUBLICATIONS Research Publications: 1. W. Que, and S. A. Sebo, “Typical cases of electric field and voltage distribution calculations along polymer insulators under various wet surface conditions,” Proceedings of the 2002 Conference on Eleetrical Insulation and Dieleetric Phenomena, October 2002, pp. 840-843. 2. W. Que, E. P. Casale and S. A. Sebo, “Voltage-current phase angle measurements during aging tests of polymer insulators,” Proceedings of the 2002 Conference on Electrical Insulation and Dielectric Phenomena, October 2002, pp. 367-370. vm 3. E. P. Casale, W. Que and S. A. Sebo, “Distribution of sait contamination in the course of fog chamber tests of polymer insulators,” Proceedings of the 2002 Conference on Electrical Insulation and Dielectric Phenomena, October 2002, pp. 359-362. 4. W. Que, and S. A. Sebo, “Electric field and potential distributions along dry and clean non-ceramic insulators,” Proceedings of the Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference, October 2001, pp. 437- 440. 5. W. Que, and S. A. Sebo, “Electric field and potential distribution along non-ceramic insulators with water droplets,” Proceedings of the Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference, October 2001, pp. 441- 444. 6. W. Que, and S. A. Sebo, “Electric field distribution in air for various energized and grounded electrode configurations,” Proceedings of the 2000 Conference on Electrical Insulation and Dielectric Phenomena, October 2000, pp. 498-501. 7. E. Wang, X. Eiang, Z. G nan, and W. Que, “Research on 500 kV phase to phase composite spacer for compact lines,” Proceedings of the 6th International Conference on Properties and Applications o f Dielectric Materials, June 2000, Vol. l,pp. 346-349. 8. S. A. Sebo, C. M. Pawlak, D. Oswiencinski, and W. Que, “Effects of humidity correction on the AC sparkover voltage characteristics of rod-rod gaps in air up to 30 /fWHwAafk)» .EThcZticfrZ Manufacturing & Coil Winding Conference, October 1999, pp. 327-330. IX 9. S. A. Sebo, J. Kahler, S. Hutchins, C. Meyers, D. Oswiencinski, A. Eusebio and W. Que, “Effects of the insulating cylinders (guards) in various gaps - the study of AC breakdown voltages,” Proceedings of the 11th International Symposium on High Voltage Engineering, August 1999, Vol. 3, pp. 63-66. 10. S. A. Sebo, J. Kahler, S. Hutchins, C. Meyers, D. Oswiencinski, A. Eusebio and W. Que, “Effects of the insulating sheets (barriers) in various gaps - the study of AC breakdown voltages and barrior factors,” Proceedings of the 11th International Symposium on High Voltage Engineering, August 1999, Vol. 3, pp. 144-147. 11. C. M. Pawlak, D. Oswiencinski, W. Que and S. A. Sebo, “Influence of rod electrode orientation on power frequency AC sparkover voltages of small air gaps,” Proceedings