Procedure

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Overview

This Technical Specification applies to hybrid insulators for a.c. and d.c. applications consisting of a load-bearing insulating solid or hollow core consisting of ceramic or glass, a housing (defined geometry, outside the insulating core) made of polymeric material and end fittings permanently attached to the insulating core. Hybrid insulators covered by this technical specification are intended for use as suspension/tension line insulators, line post insulators, station post insulators and hollow core insulators for apparatus. The object of this technical specification is to: - define the terms used; - prescribe test methods; - prescribe acceptance criteria. Silicone or other functional coatings (CIGRE Technical Brochure No. 478, Appendix B), booster sheds, shed extenders and rain deflectors are not within the scope of this technical specification. This technical specification does not include requirements dealing with the choice of insulators for specific operating conditions. Hybrid insulators consist of an insulating core, bearing the mechanical load protected by a polymeric housing, the load being transmitted to the core by end fittings. Despite these common features, the materials used and the construction details employed by different manufacturers may be quite different. The core is made of ceramic or glass material. Hybrid insulators are applied as overhead line, post or hollow core equipment insulators. In order to perform the design tests, IEC 62217 shall be applied for the polymeric housing and the interfaces between core and the housing. For the core, the test standards for the respective ceramic product (IEC 60168, IEC 60383 and IEC 62155) shall be applied. Some tests have been grouped together as "design tests", to be performed only once on insulators which satisfy the same design conditions. For all design tests of hybrid insulators, the common clauses defined in IEC 62217 are applied. As far as practical, the influence of time on the electrical and mechanical properties of the components (core material, housing, interfaces etcetera) and of the complete hybrid insulators has been considered in specifying the design tests to ensure a satisfactory life-time under normally known stress conditions in service. Polymeric housing materials that show the hydrophobicity transfer mechanism (HTM) are preferred for hybrid insulators. They are applied as a countermeasure against severe polluted service conditions. Currently, no aging or pollutions tests have been developed to demonstrate this property, but CIGRE Technical Brochure 442 is available for evaluating the maintenance of hydrophobicity and HTM of polymeric shield sheath materials. Artificial pollution tests for insulators with polymeric shielding sheaths under AC and DC stress are currently being developed by CIGRE. The responsible committee is DKE/K 451 "Isolatoren" ("Insulators") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.

Document: references other documents

Responsible national committee

DKE/K 451 - Isolatoren