Discussion of the Article “Development of RTV Silicone Coatings in China: Overview and Bibliography,” by Zhidong Jia et al., published in March/ April 2008 issue of the EI Magazine, pages 28–41. Readers of this article on the history of silicone rubber coated insulators in China may be interested in earlier development of this technology in the West. The application of hydrophobic silicone greases on insulators operating in contaminated service started in the late 1940s, but the application was labor intensive and expensive, which made for a strong incentive to find a better and cheaper solution. To our knowledge the first paper describing the evaluation of a silicone rubber coated porcelain insulators was written by a Texas Utility Engineer in 1966 . In 1971 a paper described the relationship between surface energy and the organic substitutions in the silicone chemical structure of a silicone rubber coatings developed for insulator applications . This paper also discusses the retention and recovery of hydrophobic properties after exposure to sunlight, weathering, contamination, corona, and arcing. In 1991 a digest of literature of surface dielectric of polymer insulation was written , and the literature reference list contained many papers dealing with silicone rubber coated insulators. From 1990 to 2005 a very large number of papers on this subject were published. Most of these are IEEE papers that are easy to retrieve. However, some papers were published in polymer science journals, and a paper written by J. Kim in 2001  contains some of these references.
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 J. C. Thompson, “Insulator contamination—the problem,” 19th Annual Power Distribution Conf., Univ. of Texas, Oct. 1966. 2] R. G. Niemi, “Self-priming silicone elastomeric coatings for high voltage insulators,” Proc. 10th Electrical Insulation Conf., No. 71C38, Sept. 1971.  R. S. Gorur and T. Orbeck, ”Dielectric Behaviour of polymer insulators under HV conditions,” IEEE Trans. on Elect. Insul., vol. 26, pp. 1064–1072, Oct. 1991.  J. Kim, M. Chaudhury, M. Owen, and T. Orbeck, “The mechanisms of hydrophobic recovery of polydimethylsiloxane elastomers exposed to partial electrical discharges,” J. Colloid Interface Sci., vol. 244, pp. 200–207, 2001.
Tor Orbeck, West Branch, Michigan Michael J. Owen, Midland, Michigan
Authors’ Response The authors thank the discussers for their good review of the knowledge of this technology in the West. The four references listed by them are very significant and informative. Due to historical reasons, the development of RTV silicone coatings in China was much later than in the West. However, since the first introduction of this technology by J. Xue in 1987 , many Chinese researchers and electrical engineers have focused their attention on this area, which has led to much progress. Our paper attempts to summarize some of this progress, not always from a technical point of view but with a more or less philosophical view according to the practical situation of China, which may help clarify in which direction more progress is needed. Therefore, the article is neither a technical or historical review, nor is it an introduction to the technical papers in China, but, rather, it is a melange of these aspects.
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In our point of view, the most outstanding contributions Chinese researchers have made are listed below: 1. Numerous investigations were done to describe the hydrophobicity mechanism. A paper  used the modified theory of absorption and cohesion between a solid and air to explain how the accumulated contamination on RTV-coated surfaces can become hydrophobic, and this paper proposed that the hydrophobicity transfer of RTV coatings is not only dependent on ingredients but also on some outside conditions. 2. Many Chinese researchers have tried to increase the level of feedback of actual performance from the field. They have also attempted to relate laboratory aging to field aging. A paper written by H. Gao  contains some of these results. J. Q. Xue and X. D. Liang, “New type of antipollution coating for porcelain insulators,” News of Transmission Lines, no.1, pp. 66–69, 1987. Z. D. Jia, H. F. Gao, Z. C. Guan, L. M. Wang, and J. Yang, “Study on hydrophobicity transfer of RTV coatings based on a modification of absorption and cohesion theory,” IEEE Trans. Dielect. Elect. Insulation. vol. 13, no. 6, pp. 1317–1324, Dec. 2006. H. F. Gao, Z. D. Jia, Z. C. Guan, and K. N. Zhu, “Investigation on field-aged RTV-coated insulators used in heavily contaminated areas,” IEEE Trans. Power Delivery, vol. 22, no. 2, pp. 1117–1124, Apr. 2007.
Zhidong Jia and Su Fang Graduate School at Shenzhen, Tsinghua University