Assessment of field aged composite insulators

Summary

The performance of composite insulators in transmission and distribution lines is a key factor for reliability of power systems. Significant improvement has been achieved in the composite insulators technology in past 50 years and hence the usage. Various laboratory testing facilities and procedures has been developed to confirm with the withstand levels and performance of composite insulators before installation. But none of them provides the life expectancy and other degradation issues to be faced in-service. Hence, an investigation or assessment is necessary to address such issues after installation. Such assessment provides the necessary information for maintenance and replacement and also the reliability and efficiency of insulators. For this study, 25 kV composite insulators selected from three different pollution regions (coal, cement and marine) are removed from service. The samples removed from the service are of 4 to 6 years aged and affected with different contaminants which include cement, coal and marine pollution. This paper presents the various tests that are carried out to assess the performance of the field aged samples and also reports the methods including visual observation to assess the appearance of the field aged samples with relative performance of similar composite insulators with same arcing distance and creepage distance studied in comparison to various contaminants. The determination of pollution severity by equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) methods, the classification of hydrophobicity using STRI Guide and material diagnostic techniques such as Scanning Electron Microscopy and Energy Dispersive X-Ray Analysis to determine degradation are presented. the results obtained demonstrate that the hydrophobicity of composite insulator has decreased with service and variation of silicone content in different contaminated samples in comparison to virgin sample are signs of ageing. The results of different tests are compared with virgin sample and field aged samples behaviour is assessed.

Additional informations

Authors

OESTERGAARD, VERBIN, BERNASCONI, ESMERALDO, PYATKOVA, RABCHUK

Keywords

Composite Insulators, Contaminants, Material degradation, ESDD, NSDD