Standards Development

Scope

This Technical Specification applies to composite insulated cross-arms that comprise of a combination of composite suspension insulator, composite line post insulator and connection fittings. The constituent composite insulators of the insulated cross-arm consist of a loadbearing cylindrical insulating solid core for suspension insulator, and a solid or hollow core for line post insulator consisting of fibres – usually glass – in a resin-based matrix, a housing (outside the insulating core) made of polymeric material and end fittings permanently attached to the insulating core.

The composite insulated cross-arms covered by this technical specification are subjected to cantilever, tensile and compressive loads, when supporting the line conductors. These include braced line post insulators as well as assemblies composed of three or more composite insulators which are disposed three- dimensionally to provide higher vertical, transverse and longitudinal load capabilities for both suspension and tension type transmission supports. They are intended for use on overhead lines with a.c. rated voltage greater than 1 000 V and a frequency not greater than 100 Hz, and d.c. voltage greater than 1 500 V.

The object of this technical specification is to give the user means to:

—  define the terms used,

— choose appropriate specification of composite insulated cross-arm,

— prescribe test methods,

— prescribe acceptance or failure criteria.

Purpose

There is large demand for new compact overhead lines and upgrades to existing ones using composite insulated cross-arms due to the on-going energy transition. The composite insulated cross-arm combines the technology of insulators (TC 36) and overhead lines (TC 11). While composite insulated cross-arms have now been widely applied by TSOs around the world for multiple decades there are no international standards that cover them as a complete system and deal with the distinct requirements that emerge with the combination of suspension and post insulators. The lack of standardization has led to varied terminology and definitions, disparities in design requirements and inconsistent test methods.

The increased use of composite insulated crossarms at progressively higher voltages and on critical applications further amplifies the necessity for an IEC standard to assurance quality and for preventing failures in service. The proposed technical specification will enable the users to specify optimized designs and accurate ratings, and to test with greater efficiency and accuracy.