Innovative pollution and ice testing of DC composite insulators for ±525 kv DC line

Summary

Norwegian TSO Statnett has selected outdoor insulation for a new ±525 kV HVDC project, NordLink, between Norway and Germany. Part of this link will be overhead line close to the Norwegian coast and it was decided to use composite insulators for this line. In order to verify the pollution and ice performance of the insulators intended for relatively cold, humid and coastal area a special test program was developed and included the pollution testing and ice testing. At present there is no standard IEC pollution test method available for composite insulators and, especially, for DC applications. The innovative specially-developed pollution test presented in this paper used the CIGRE-recommended for AC procedure described in CIGRE TB 555, which comprises the following steps: gentle cleaning of the insulators, pre-conditioning of the surface by dry kaolin powder and application of the pollution layer by spraying. While the standard voltage application was used for the withstand test, the flashover voltage tests were performed in accordance with the Rapid Flashover Test. This procedure is described only in the draft of coming in 2017 CIGRE Technical Brochure and earlier was mostly applied for AC insulators. Detailed description of different practical steps of new procedures applied for DC composite insulators is presented in the paper. For the ice test there is also no standard IEC procedure and thus the test was constructed as a combination of relevant IEEE Standard for ice testing and IEC pollution test requirements for ceramic insulators. One V-shaped insulation structure with insulator length of more than 6 m was tested. The glaze type of ice was accreted using a structure of aluminium beams, mirroring the V-shaped insulator structure, which was hung from the crane in the climate test hall. Detailed description of different practical steps of new procedure applied for DC composite insulators is presented in the paper. The knowledge obtained as a result of the application of innovative pollution and ice tests is essential for the ongoing discussions within IEEE/CIGRE/IEC.

Additional informations

Authors

MARTÍN, Velek, SOTTERO

Keywords

HVDC, overhead line, composite insulator, pollution performance, ice performance