Technical design requirements and test experiences on Composite Hollow Core Insulators regarding pollution performance under AC and DC stress

This paper is a common approach of manufacturers of insulators, electrical equipment, transmission system and test labs to verify the expected behaviour in laboratory and outdoor tests. For the electrical design of composite insulators, different material properties and shed profiles for AC and DC conditions have to be taken into account respectively, considering the recommendations of the recently published IEC TS 60815-4 regarding DC shed profile design of composite insulators. Furthermore, test standards like IEC TS 61245 for DC pollution testing, as well as specific test specifications were investigated, with respect to the applicability of the test methods on composite hollow core insulators of different diameters.
The laboratory tests consist of artificial pollution tests on hollow core insulators of 2 to 3 meters length and different diameters. The test procedures were based on the solid layer and the salt fog methods as described in IEC TS 61245. To compare the flashover values gained by these tests, the new diameter correction approach of IEC TS 60815-4 was used and showed a good correlation of the corrected flashover values in respect to the Salt Deposit Density (SDD). The experimental tests have been performed in cooperation with Siemens AG and GE power Grid Solutions S.p.A. Bushing division.
To gain long term experience and verifying the laboratory tests, two support insulator assemblies were placed in an outdoor EDF test facility in Martigues. This test facility is located in the south of France, close to the coastline and is characterized by very severe marine and industrial pollution (oil refineries and power plant). First measurements show a site pollution severity class of “medium” up to “heavy”.
In the conclusion of the paper, the test results are discussed with their contribution to different application requirements regarding pollution issues .
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