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132 kV power lines in the UK

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Overview

132 kV is England’s highest distribution voltage; 275 kV and upwards are transmission voltages, although it appears that Scotland still considers 132 kV to be a transmission voltage. The National Grid was originally constructed as 132 kV, onto which the 275 and later 400 kV Supergrid circuits were overlaid. Most 132 kV lines are now divested out of National Grid and are the responsibility of the regional distribution operators. 132 kV is also the highest voltage to be carried by wood pole lines.

132 kV lines can be carried on a number of support types:

Supports

Wood pole 132 kV circuits do not use an earthwire, while those on metal poles and pylons do have an earthwire.

Trident poles

Trident poles are notable for their three upward-facing post insulators. The centre post insulator is vertical, while the two side ones lean outwards on intermediate poles. (Section and angle towers have all vertical insulator posts.)

The Trident design covers both single poles and so-called “H-poles”, although the latter type is more akin to a capital letter pi “Π” than “H”.

Trident poles are conventionally made from wood. British Power International’s Protean page shows a Protean metal Trident pole.

The different Trident pole types are illustrated on page 11 (PDF page 13) of Reinforcement to the North Shropshire Electricity Distribution Network document 5.2: Flood Risk Assessment. The Trident types are also illustrated in SP Energy Networks document Figure 2.1: Typical Wood Pole (Component Parts of 132kV 'Trident' Design Wood Pole), which depicts a straight rather than tapered crossarm style on the section poles. The rear “insulators” on the terminal pole are in fact surge arresters.

Fork poles

Similar to Trident, but the insulators are vertical. The real designation is not known. There are also fork H-poles (akin to Trident H-poles), and super-strength fork poles, again all of unknown designation. These types can all be found in Scotland.

Metal poles

Multiple metal pole types exist. Details on 132 kV poles are not clear. Flickr photo 43-97 Pole Top depicts a “43-97” pole, which refers to ENA TS 43-97. It is possible that multiple manufacturers have produced poles to this design, which would account for the variations in design. The same photographer also depicted a 43-97 Angle Pole which is similar in design to those seen in Clapham in Bedfordshire but nonetheless different, with a stouter pole and a different crossarm attachment method. These are examples of folded-plate poles. Both single and double circuit types exist in the UK; a double-circuit example can be seen on Flash Bristow’s Pylons around the UK page.

“PB” is a double earthwire, single circuit 132 kV twin mast support system designed and fabricated by Painter Brothers, part of their Painter’s Universal Pole family.

EaSTS—Earthed Steel Trident Structures—is an SSEN pole type developed by Energyline. Although it borrows the “Trident” name, there is a suggestion that the intermediate poles have all vertical insulators instead of Trident’s characteristic splayed design. EaSTS is said to cost £700,000 per kilometre versus £3,000,000 per kilometer for steel lattice towers.

Unidentified type found in Yorkshire, upgraded from single to double circuit.

Pylons

There are many lattice tower (“pylon”) types designed to carry 132 kV. Some 132 kV lines are even carried on Supergrid towers. See the pylons section for more details.

Composite poles

Composite poles were chosen for the double circuit 132 kV line between Blackhillock substation and the Dorenell wind farm, Scotland; this 140-support line went live in 2018. According to the Construction Enquirer article Balfour Beatty pioneers plastic pylons in Scotland, steel towers were rejected due to “cumulative impact in the local area” and the option of two parallel Trident (wood pole) circuits was rejected due to land usage footprint. The composite pole design still requires two poles, but they are close together, similar to the twin pole 33 kV system. The article notes that “traditional” timber pole lines have a 40-year lifetime and the composite poles double that. The NS Energy article SSEN energizes 220MW Dorenell wind farm in UK also covers this line.

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