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Composite Long Rod Insulator

Composite Long Rod Insulator is a load-bearing suspension and tension insulator used on overhead power lines to mechanically support conductors while providing electrical insulation, typically in AC systems above 1,000 V and DC systems above 1,500 V. Defined by IEC 61109:2025, it consists of a glass-fibre reinforced resin core with a polymer housing and permanently attached metal end fittings, and is valued in transmission projects for its high mechanical strength, strong creepage performance, and good contamination resistance. In practice, selection depends not only on voltage and load, but also on creepage distance, nominal length, end fitting type, and specified mechanical load, with typical utility specifications for high-voltage lines including 400 kV ratings, 120 kN or 160 kN strength classes, and strict dimensional tolerances such as ±10 mm overall length and no more than 1% shortfall in nominal creepage distance.

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Product Accessories

Corona rings are used on higher-voltage long rod assemblies to smooth the electric field around the end fittings and reduce corona and partial discharge stress.

Arcing horns or arcing protection devices are fitted where required to guide arc energy away from the insulator body during switching or fault events.

Ball-and-socket fittings and clevis-and-eye fittings are the standard long rod end types referenced in technical specifications, with the choice made to suit the tower and conductor arrangement.

Locking devices such as split pins are used to secure the coupling hardware, with stainless steel preferred in published utility guidance.

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Product Specifications

Product type

Composite suspension/tension long rod insulator for overhead lines.

Standard

IEC 61109:2025.

Voltage scope

For AC systems greater than 1,000 V and DC systems greater than 1,500 V.

Core construction

Load-bearing cylindrical insulating solid core made of fibres, usually glass, in a resin-based matrix.

Housing material

Polymeric housing surrounding the core.

End fittings

Metal end fittings permanently attached to the core.

End fitting styles

Ball-and-socket and clevis-and-eye are the standard long rod coupling forms.

Mechanical ratings

Long rod insulators are specified by routine test load and specified mechanical load; published 400 kV examples include 120 kN and 160 kN classes.

Electrical design basis

Insulation performance is determined mainly by creepage distance and arcing distance, with open aerodynamic sheds recommended for polluted conditions.

Dimensional control

A published long rod specification limits overall length tolerance to ±10 mm and requires nominal creepage distance not to fall short by more than 1%.

Product Applications

Economy is more affordable

where the line needs high mechanical strength, ball-and-socket couplings, and an open shed profile with self-cleaning behavior.

400 kV transmission suspension strings in very heavy polluted areas
on overhead lines, including string arrangements using 120 kN or 160 kN mechanical classes for heavy conductor loading.

400 kV tension and dead-end sections
where long rod construction is chosen to simplify line hardware and maintain dependable insulation performance under outdoor exposure.

New overhead line projects with compact tower geometry
where the shed profile, creepage distance, and arc-protection package are selected to handle contamination and moisture.

Replacement of conventional string insulators in polluted or foggy industrial corridors

Product Advantages

High mechanical capability in a single composite body

The long rod format is built for suspension and tension duty, with published 400 kV projects using 120 kN and 160 kN classes.

Cleaner outdoor performance

Open aerodynamic sheds and self-cleaning profiles help the insulator stay reliable in fog, dust, salt, and industrial pollution.

Flexible, standardized line hardware

Ball-and-socket or clevis-and-eye end fittings, plus optional corona rings and arcing protection devices, make the product easier to adapt to different tower and conductor layouts.

WellDone Composite Long Rod Insulator Plan Drawing

FAQ

What is a Composite Long Rod Insulator used for?

It is used as a suspension or tension insulator on overhead lines to hold the conductor mechanically while keeping it electrically isolated.
Where is it commonly installed?

It is commonly used on high-voltage transmission line suspension strings, tension strings, and dead-end sections, especially in polluted outdoor corridors.
Why choose a composite long rod design?

It combines strong mechanical performance, a self-cleaning shed profile, and flexible end-fitting options for demanding overhead line service.