2001 | OriginalPaper | Buchkapitel
Field Monitoring of the Ageing of Composite High Voltage Insulators
verfasst von : Graeme A. George, Gregory A. Cash, Heping Liu, Ben G. S. Goss, David Birtwhistle, Andrej Krivda
Erschienen in: Ageing Studies and Lifetime Extension of Materials
Verlag: Springer US
Enthalten in: Professional Book Archive
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Composite high voltage insulators have been introduced in power networks throughout the world to replace ceramic insulators. Particular advantages include low weight, vandal resistance and lower discharge and electrical interference. The disadvantage, and thus the challenge in management of large populations of composite insulators, is the possible loss of insulation properties on environmental ageing, leading to uncertainty as to the safe useful lifetime of the insulator. One approach which exploits the extensive understanding of the degradation mechanism of elastomers such as EPDM, is to assess the condition of the shed by identifying the oxidation products removed by a non-destructive surface sampling method, including a remote live-line sampling tool. A xylene impregnated swab is used to remove surface material from representative sheds. The swabs are analysed by FT-IR emission spectroscopy (IES) and examination of the carbonyl region of the emission spectrum allows relative amounts of the different oxidation products to be determined. Analysis of a large number of insulators from widely varying environments has shown that there is a variation in the extent of oxidation and product distribution which is consistent with corona discharge, ozone damage and extensive UV exposure. By using cluster analysis on the growing database of insulators which have been sampled, it is possible to determine the predominant mode of degradation in particular geographical locations as well as assessing which commercial insulator showed higher durability in the particular environment. The use of IES has been complemented by diffuse reflectance IR for the analysis of chalking of filler and SEM and XPS analysis on thin slivers of polymer to determine the extent of microcracking, depth of degraded layer and elemental composition. Cluster analysis has also been performed on these data to provide a total picture of the degradation of composite insulators and so guide the procurement, maintenance and replacement strategies of the power distribution authorities.