Evaluation of Station Post Porcelain Insulators with Room Temperature Vulcanized (RTV) Silicone Rubberr Coatings

(PSERC) is a multi-university Center conducting research on challenges facing the electric power industry and educating the next generation of power engineers. Notice Concerning Copyright Material PSERC members are given permission to copy without fee all or part of this publication for internal use if appropriate attribution is given to this document as the source material. This report is available for downloading from the PSERC website. Acknowledgments This is the final report for PSERC project " Evaluation of RTV Coated Station Insulators " (Project T-46G). The project is a targeted research project supported by additional membership funds provided by San Diego Gas & Electric. Thanks are given to William Assurian and William Torre at SDG&E for their assistance in this project. Several methods are presently available to improve performance of station insulators under contaminated conditions, of which the application of hydrophobic coatings (like grease, oils and room temperature vulcanized (RTV) silicone rubber material, fluorinated compounds) are attractive to utilities as it can be applied over existing installations. Of the hydrophobic coatings, RTV silicone rubber has proven to be the most popular type. The chief concerns with this method are the time of effectiveness of the coating, and insulator performance with time in service. This project describes the testing and analysis of porcelain post insulators that were coated with a room temperature vulcanized (RTV) silicone rubber material. The tests were performed in a fog chamber using the clean fog method and the insulators were artificially contaminated with different levels of contamination ranging from light to very heavy (as expressed by equivalent salt deposition density-ESDD). It was found that the RTV coated insulators were able to withstand levels of contamination that are far higher than experienced in the SDG&E service territory. The adhesion of the coating to the porcelain was excellent even after many tests which involved substantial surface discharge activity. Statistical analysis was performed to quantify the improvement provided by the RTV coating when it had completely lost its hydrophobicity. It was found to in the range of 15-40%, the higher number for 69 kV system voltage and the lower number for 230 kV system voltage. In practice, this number should be higher than these as the protected surface of the insulator sheds are usually hydrophobic.