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Composite Line Pin (Post) Insulator

Composite Line Pin (Post) Insulators are polymer insulators used on AC overhead lines above 1,000 V, built with a fiberglass load-bearing core, a silicone rubber housing, and permanently attached end fittings. Common in 11 kV, 22 kV, and 33 kV distribution systems, they are designed for overhead lines and substations where weather resistance, self-cleaning performance, and long service life are important. Their selection is mainly based on electrical withstand strength, creepage distance, and mechanical load capacity, with MDCL as a key mechanical parameter; typical utility requirements include high impulse withstand voltage, sufficient wet and dry withstand performance, and cantilever or breaking load values suited to line service.

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Product Accessories

Steel pin sets are used on pin-post versions to support the insulator on the crossarm or mounting base, and utility documents specify that the insulator should be supplied complete with the necessary pin hardware.

Nuts and spring washers are part of the fixing package for base mounting, helping secure the assembly to the support frame.

Crossarm or channel-iron mounting hardware is used where the insulator is fixed to a 100 × 50 × 6 mm crossarm section in the utility specification.

Conductor seating grooves are built into the top or side profile to accept AAC, AAAC, and ACSR conductors, with a minimum groove radius of 16 mm noted in one utility specification.

Corrosion-resistant mounting parts are commonly used in station and line hardware packages, while standard post-line product families also offer corona rings where required for installation conditions.

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Product Specifications

Product type

Composite line pin/post insulator for overhead line support and isolation.

Standard basis

IEC 61952-1 for composite line post insulators.

Voltage scope

Applicable to AC overhead lines above 1,000 V; common distribution use is 10 kV to 33 kV, with utility examples at 11 kV/12 kV and 33 kV/36 kV.

Core material

Fiberglass / glass-fibre reinforced insulating core in a resin-based matrix.

Housing material

Polymer housing, typically silicone rubber for outdoor line service.

Mechanical rating

MDCL / minimum failing load is a key specification; utility examples show 10 kN for 11 kV and 33 kV pin/post units, while a 24 kV composite line post example is rated at 15 kN breaking load.

Creepage distance

Utility examples show 310 mm and 950 mm for pin post classes, and 480 mm for a 24 kV composite line post model.

Electrical withstand values

A published 24 kV composite line post example lists ≥125 kV dry lightning impulse withstand and ≥50 kV wet power-frequency withstand.

Conductor compatibility

Designed to accept AAC, AAAC, and ACSR conductors; one utility spec notes an applicable conductor size up to 28.7 mm.

Mounting interface

Pin/post versions use a steel pin and crossarm fixing arrangement; one published composite line post model uses an M20 × 140 bolt.

Product Applications

Economy is more affordable

on pole-top structures where the conductor must be held safely above the crossarm and hardware. Utility specifications explicitly cover composite pin post use in these voltage classes.

11 kV and 33 kV overhead distribution feeders
where the top/side conductor groove and compact support shape simplify line hardware installation.

Town and suburban branch lines with AAC, AAAC, or ACSR conductors
especially where a standard fixing arrangement and predictable creepage distance are needed.

Crossarm-mounted support points on channel-iron or steel pole structures
where silicone sheds and self-cleaning behavior help maintain surface performance.

Medium-voltage overhead sections exposed to pollution, moisture, and frequent cleaning cycles

Product Advantages

Lightweight and easier to install

Composite line post insulators are lighter than porcelain alternatives, and some designs eliminate the need for separate pulling wheels during installation.

Strong outdoor performance

Silicone sheds provide UV resistance and self-cleaning behavior, which helps the insulator stay reliable in wet or contaminated environments.

Stable electrical and mechanical design

The product is specified around creepage distance, impulse withstand, and MDCL, which gives line designers a practical way to match the insulator to real service conditions.

WellDone Composite Line Pin (Post) Insulator Plan Drawing

FAQ

What is a Composite Line Pin (Post) Insulator used for?

It is used to support and insulate overhead line conductors on medium-voltage distribution structures.
What voltage levels are most common?

Common utility ratings are 11 kV/12 kV and 33 kV/36 kV, with many line post products also used in the 10 kV to 33 kV range.
What makes the composite design attractive?

It is lighter, weather-resistant, and designed for dependable outdoor performance with good creepage and mechanical strength.