EVALUATION OF OHL PERFORMANCE BASED ON ENVIRONMENTAL STRESSES AND POLLUTION LABORATORY TESTING OF COMPOSITE INSULATORS

摘要

This paper makes an analysis of the state-of-the-art of Approach B (Measure pollution severity at the site and dimension based on laboratory test results) according to the revised version of IEC 60815-1, to be issued in 2008. In this paper the approaches in four different countries i.e. China, Russia, South Africa and Sweden are compared. The artificial pollution tests developed in these countries are very similar and similar results are obtained. The laboratory tests are in principle the same as prescribed by the IEC for conventional insulators (Solid Layer test according to IEC 60507/IEC 61245) but with the addition of a preconditioning phase where the hydrophobic properties of the insulators are masked by the application of an inert powder. Test results presented show that this modification results in good repeatability of the obtained test results. This new method was successfully applied for the tests of line composite insulators intended up to 1150 kV AC and up to 800 kV DC OHL. The reproducibility of the test was confirmed in two HV laboratories. This suggests that the pollution test for composite insulators is reaching maturity and can be considered for standardization by CIGRE/IEC. At present most of the composite insulators are tested in the fully hydrophilic state, which is a conservative approach as in most environments silicone rubber normally retains its hydrophobicity. The presented test method can easily be modified with the addition of a fixed recovery time to allow for the quantification of the ability of an insulator to regain its hydrophobic properties. The results of the pollution tests described in this paper are directly applicable to the statistical dimensioning of the insulation of the overhead lines (OHL). Such calculations used pollution stress evaluation based on pollution monitoring results and pollution flashover performance curves obtained in the laboratory (or at the test stations).