A Novel Technique for Conducting Solid Layer Pollution Test on Polymeric Insulators
Pollution accumulation over the insulators is the major cause of failure in outdoor electrical systems where a flashover can occur even under normal working voltages. Pollution performance of is thus an important parameter in dimensioning of insulators. Presently polymeric insulators draw the attention of utilities and manufacturers as their pollution performance is superior to the conventional insulators. But, lack of standardized test method to check the pollution performance of composite insulators still remains confusion in selection of insulators for manufactures & utilities. Efforts are being made by different utilities for standardization of artificial pollution technique for polymeric insulators.
CIGRE C4.303 working group has recently proposed a procedure for pollution testing of polymeric insulators by solid layer method and is being validated through Round Robin Test. The test procedure followed is as per IEC 60507 for ceramic insulators with a deviation of preconditioning polymeric insulator with dry kaolin powder to mask its hydrophobicity before pollution application. The method also allows to test the insulator in different hydrophobicity conditions.
In present work, applicability of the Salt fog test method has been evaluated and diagnostic methods like X-Ray Diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) were carried out to check the surface behaviour of insulator. also the reproducibility of the solid layer test results is validated for Indian tropical conditions as per the CIGRE procedure. Different approaches have been used to control the surface property of the polymeric insulator. Though preconditioning of insulators with dry kaolin powder will not mask the hydrophobicity it provides an access for better adhesion of pollution layer. Solid Layer method of pollution testing is applied to the insulator to check the withstand capabilities with different Salt Deposit Density values. It was possible to achieve the best results by coating the pollution layer after precondition test. The analysis and results are presented.