An Improved Pollution Testing Methodology for Polymeric Insulators: Analysis on Surface Coating and Flashover Voltage Under Solid Layer Test

Abstract

Polymeric insulators have found application worldwide in outdoor insulation system due to their better pollution performance. Since there are no standard laboratory test methods to analyse pollution performance of polymeric insulators, selection and dimensioning of proper insulator is still confusion for engineers and utilities. IEC and CIGRE working groups have recently suggested a test method for solid layer pollution testing of polymeric insulators. The uniformity of pollutant coating over hydrophobic insulator surface was not consistent with CIGRE Round Robin Test procedure. In this research work, a method of soaking the insulators in water as a part of preconditioning before actual pollutant spray was adopted and uniformity of coating was compared with CIGRE round robin test procedure. Critical analysis has been made on the loss and recovery of hydrophobicity characteristics on silicone insulators and its ability to transfer the hydrophobicity to pollution layer were observed and recorded over a period of 15 days with the proposed coating method. Solid layer pollution test was carried out on 66 kV long-rod insulators with the proposed test procedure and the results were compared with CIGRE procedure. 50% Flashover Voltage (U50%) of the insulator was determined before and after withstand test for both the test methods and standard deviation was calculated. The variation in the flashover voltage values has been calculated before and after withstand test. From the results, it’s been observed that, the hydrophobicity character was not influenced to the pollution layer in the given recovery period but the recovery time had an impact on flashover voltage. The deviations in flashover voltage value compared before and after withstand tests, found to be within 5% for both CIGRE procedure and modified test procedure.