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Evaluation of station post porcelain insulators with RTV silicone rubber coatings

All porcelain insulators coated silicone rubber coatings, this article is the evaluation of station post porcelain insulators with RTV silicone rubber coatings.

station post porcelain insulators

Summarization:
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.

Introduction
The reliability of a power system is reduced whenever the flashover strength across an insulator falls below the breakdown strength of the air in its working environment. Mitigation of outages due to lightning or switching surges is a well discussed topic among the industrial and academic communities. However, contamination caused flashovers are still a major problem.
Contamination flashover is a complex problem faced by utilities today which have a wide geographical working span. Different types of pollutants on the insulation equipment are encountered due to various environmental conditions. The outdoor insulation equipments used in substations, overhead transmission and distribution lines must withstand the over-voltages due to switching or lightning transients in addition to their service voltages. The performance of insulation in contaminated conditions is paramount for providing a reliable service to the end user.
The utilities are able to select the insulator type according to the system and design requirements.
In order to improve the contamination flashover performance, the utilities need to opt for high leakage porcelain (HLD) units, which can be taller or have wider sheds than standard porcelain units. However, for an optimal design of substation insulation it is desirable to improve the contamination flashover without increasing the height or width of the unit.
Room temperature vulcanized (RTV) Silicone Rubber coated insulators is a practical option for improving the flashover performance in presence of the pollution without compromising on the mechanical aspects of the substation design. The motivation of this study is to compare the performance of bare and RTV Silicone Rubber coated porcelain insulators by performing accelerated aging tests in the laboratory. Overall assessment of several important aspects of the coating such as adhesion to porcelain, hydrophobicity, contamination flashover performance and weathering is provided in the study. A good theoretical model for predicting the flashover will be a desirable asset to the utilities, helping to improve the substation design in the future. The study aims to build a comprehensive model for predicting the flashover performance of the RTV coated insulators.

For example, station post porcelain insulators using silicone rubber coatings
Twelve 69 kV post insulators were provided by San Diego Gas and Electric (SDG&E). The insulator units were manufactured by NGK-Locke Inc. Eleven samples were coated with Room
Temperature Vulcanized (RTV) Silicone Rubber by a private contractor also provided by SDG&E.
The RTV Silicone Rubber coating was applied in a dust-free spray booth facility available at the Arizona State University Campus. After, the coating, the samples were left to dry for one day before subjecting to laboratory tests.
Artificial contamination tests provide valuable information on the behavior of external insulation by simulating the service environment in lab conditions. The contaminants consist of a suspension prepared by mixing appropriate proportions of kaolin and common salt (NaCl) in demineralized water.

Station post porcelain insulators using silicone rubber coatings used outdoor have long service life and good pollution performance.

 

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