A round robin test of the water induced corona test

There is an exponential growth in application of composite insulators during the last decade(s). They are especially popular for overhead line refurbishment and compact lines and these applications require higher demands on electric field grading. Two main criteria are used for the dimensioning of grading rings for composite insulators, the first one for the metal parts and the second for the housing of the insulator. If the second criterion is not fulfilled, deterioration of the surface could occur due to water induced corona. STRI has developed a test method to verify the second criterion on full scale products. This test method was repeatable and has been used by STRI with success in several practical applications. The goal of this paper was to verify further application of the test method internationally. Thus, for the evaluation of the reproducibility a Round Robin Test in five different laboratories was performed with very positive results.