Since silicon rubber insulator(SRI)has hydrophobicity,its salt dissolving in pollution is more complicated than that of insulators of hydrophilic inorganic materials.Therefore it is necessary to study the leaching process,as well as the amount of salt in the process,on wet polluted SRIs.We proposed the effective equivalent salt deposit density(EESDD)to characterize the amount of dissolved salt of different wet pollution layers on SRIs.We also designed a convenient method for testing EESDD,which included hydrophobic grading measurements.EESDD test results of both artificial and natural contaminated SRIs show that EESDD is a part of ESDD:the ratio between EESDD and ESDD is generally within 50%~90% and it increases with the reduction of pollution hydrophobicity.The EESDD is relatively larger when the ratio of NSDD and ESDD is less than 4.Based on the analysis of test results,it is suggested that the pollution test should be combined with hydrophobicity measurements of SRIs,and the dimensioning of SRIs should be based on EESDD rather than the site map of ceramic insulators.

Concept and Test Method of Effective Equivalent Salt Deposit Density for Silicone Rubber Composite Insulators

Performance of an insulating dielectric may decrease due to aging. The main cause of aging on insulator is contaminant arising on the insulator surface. In this study, effects of contaminants on the coating large leakage current on the surface of the polymer insulator are investigated. To analyze the effects, accelerated age testing module as a form of pre-conditions on polymer insulator aging is designed. Furthermore, dielectric strength testing is performed to determine the effect of contaminants on pre-breakdown voltage. The results of this study showed that the thickness level of contaminants on the surface of the layer affects insulator leakage current and pre-breakdown voltage.

Analysis of contaminant effect on ceramic & polymer insulator surface under artificial environmental condition

Compared with traditional ceramic and glass insulators, aging phenomena of composite insulators is much more serious. High temperature, high humidity and heavy sea fog in coastal area pose great challenge to the operation of composite insulators. However, the effect of relatively complicated surrounding on composite insulator ageing is not clear yet. In this paper, a multi-factor aging system simulating costal climate is constructed, and the experimental parameters are set according to the condition in field. After the samples are aged in the system, comprehensive characteristics of aged HTV silicone rubber samples with different contamination grade and other conditions are measured, including the physical property such as hydrophobicity, the electrical property such as trap distribution and surface resistivity. To analyze the gradual changes of micro-surface condition, SEM are employed. Experimental results show that the salt contamination greatly affects the surface microstructure of HTV silicone rubber materials. Salt contamination has great influence on the loss of hydrophobicity, and with the aging time increasing, the static contact angle of four different samples showed a declining trend. Surface resistivity decrease with the development of corona aging. More contamination the sample has on its surface, lower the surface resistivity of the sample is. Moreover, with the samples aging, the trap density of aged samples with different salt contamination will increase finally.

Bin Wei

Papers

Influence of salt contamination on multi-factor corona ageing characteristics of HTVSilicone rubber insulating material