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Infrared analysis of dry-band flashover of silicone rubber insulators

Albano, Maurizio, Waters, Ronald T., Charalampidis, P., Griffiths, Huw and Haddad, Abderrahmane 2016. Infrared analysis of dry-band flashover of silicone rubber insulators. IEEE Transactions on Dielectrics and Electrical Insulation 23 (1) , pp. 304-310. 10.1109/TDEI.2015.005026

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Abstract

Wetting of a pollution layer by mist or light rain is inhibited, in the case of silicone rubber (SiR) insulators, by the migration of hydrophobic polymeric chains from the insulator to the layer surface. However, recent laboratory fog-chamber tests have shown that a salt/kaolin layer applied to the surface of an 11kV SiR insulator can reduce the specific creepage distance (SCD) at flashover to as low as 16mm/kV. Even for larger values of SCD, potentially damaging partial arcs can arise along the insulator surface. It has been shown that some mitigation of partial-arc activity and an increase of flashover voltage can be achieved by appropriate texturing of the SiR insulator housing. The present paper describes additional infrared (IR) recording which accompanied these previous tests. Although a reduction of the flashover voltage in polluted environments is generally surmised to be the result of the formation of dry bands in a conducting moistened surface layer, no direct observations of dry bands appear to have been previously demonstrated in the laboratory. Such observations are described here, where details of dry-band location and growth are revealed by IR recording. Dry bands are shown by close-up visual photography to be invariably bridged by small streamer/spark discharges which maintain current continuity in the pollution layer. Local surface heating by these discharges are the probable cause of the delayed rewetting of the bands. Partial-arc channels that may result in flashover develop from and across the dry-band streamers. It has become clear that clean-fog testing with infrared recording and leakage current measurements provide new possibilities for the modeling of dry band discharges and improvement of insulator design.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Publisher: IEEE
Funders: EPSRC
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 1 October 2015
Last Modified: 29 Jun 2019 04:31
URI: http://orca.cf.ac.uk/id/eprint/84174

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