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“PB” 132 kV portals

Contents

Overview

“PB” refers to a series of single circuit, double earthwire 132 kV overhead line supports of portal construction, part of the Painter’s Universal Pole (PU Pole) family. On their old website (now defunct), EDS Consultancy described the design as follows:

A 1950’s vintage, 132kV single circuit mast line using steel channels, designed by Painter Brothers, carrying 175mm2 ACSR conductors in flat formation, with two over-running 70mm2 earth-wires.

SP Energy Networks’ 132kV Overhead Lines Strategy, an annex of their 2015–2023 Business Plan (updated March 2014) also depicts this support type and refers to it as “PB”.

PB structures are built around twin “PB” poles, each pole formed from back-to-back pairs of channels joined by zig-zag bracing. The poles are orientated transversely for the intermediate portals and longitudinally for the angle portals. The term “PB” appears to have been adopted for the completed structures also. While the intermediate structures are self-supporting, the section supports are guyed. Painter Brothers SS35/SS60 drawing 3515 gives the normal span as 750 feet, 75% of the standard span of a steel tower line. SP Manweb gave the spacing as 180–215 m in drawing D700.008 (support type comparisons for Legacy–Oswestry), equivalent to 590–705 feet.

Designation for the intermediate portal as “SS0” (single circuit, double earthwire, no deviation) comes from the former EDS website.

General data

Manufacturer Painter Brothers
Found England Wales
Height (straight line portal) ca. 43′–3″
Voltage 132 kV
Dates back to 1955 (drawings)
Conductors Single
Circuit count Single
Design conductor 0.175□″ SCA (now 175 mm² Lynx ACSR)
Design earthwire 0.07□″ SCA (now 70 mm² Horse ACSR)
Normal span 750 feet

Pole structure

Each support is formed of two poles in a portal arrangement. Each pole comprises a pair of steel channels joined by interior bracing. In 132kV Overhead Lines Strategy, SP Manweb measured the channels as 8″ by 2.38″ (2.38″ possibly being rounded from 2⅜″, which is 2.375″); as they illustrated an SS0 portal, the dimensions should be assumed to be valid for SS0. These dimensions match what Painter Brothers illustrated for SS35/SS60. For SS35 and SS60 the complete poles are 1′–8⅜″ × 8″ in total cross-section area; whether this holds for SS0 is not known but it does appear to be the case. The diagram below illustrates the cross section of a single SS35/SS60 pole, approximately to a scale of 1 cm per inch:

Lines

Lines discovered to date include:

Structure forms

The following diagrams are shown to scale at 12 pixels per metre:

“PB” SS0
“PB” SS5?
“PB” SS35/SS60

SS0 is shown in SP Manweb comparison diagram D700.008, of which Rev F can be found as figure 4.1 of a document with a hopelessly long title:

PROPOSED REINFORCEMENT TO THE ELECTRICAL DISTRIBUTION SYSTEM
132kV Overhead Line Between Legacy and Oswestry
Environmental Statement
Volume 2 : Figures

The SS0 diagram is manually traced from the aforementioned diagram and from photographs taken in Dorset by Christopher Aldridge (see Flickr links at end of page). The longitudinal view is estimated very approximately from Google Street View.

SS35 and SS60 seem to be visually identical and share the same general arrangement drawing. The foundations for SS35 are 2′–9″ square, while those of SS60 are 3′–3″ square, regardless of portal height. SS35 uses No. 10 SWG stays (3.251 mm diameter), while SS60 uses stronger No. 8 SWG (4.064 mm diameter) stays; these figures appear to refer to the strand thickness of what appears to be 19-strand wire rope (steel cables) in each case.

There are a small number of tension portals of a low-deviation-angle type. A summary investigation has shown SS35 to be used at deviations as low as 6°, while the deviation angles used for the lesser type include 4° and 1½°. As such, this type may be SS5, rather than SS10 or SS20. This type may also be used as the section support. Currently no details for such a type have been unearthed. Unlike SS35/SS60, this type has the poles orientated the same way as SS0, with the zig-zag facing along the line.

Structure details

Ground level size does not include stays.

Type Source Height Ground level size Crossarm width
“PB” SS0 D700.008 Rev F 10.19 m (ca. 43′–3″) ca. 5.5 m × 0.2 m 10.08 m (ca. 33′–0″)
“PB” SS35/SS60 3515 49′–0″ (14.9 m) 23′–2″ × 1′–8⅜″ (7.1 × 0.5 m) 45′–7¼″ (13.9 m)

Double-circuit upgrade

The line between Husthwaite and Wormald Green was upgraded from single-circuit twin-earthwire to double-circuit no-earthwire at some point prior to 2016. Design work for the upgrade was conducted by EDS Consultancy Limited and was briefly explained and illustrated on their old website (link under see also). As EDS explained on their website, there are difficult challenges when it comes to overhead lines. Quoting from their site:

One resolution to this predicament is to upgrade an existing line. In the case of Riley and Neate masts, EDS Consultancy designed a way to upgrade the vintage single-circuit 33 kV masts to 132 kV by replacing the crossarms with polymeric long-rod insulators. With the Painter Brothers type, the new design removed the earthwires and increased the number of conductors from three to six. Polymeric long-rod insulators were again used. Safety screens were placed between the two circuits, which can be seen on the actual structures but not in EDS’s own photos, although EDS did mention that they were fitted.

View full-size image
Upgraded PB SS0 portal
Photo “Two Powerlines Crossing near Bishop House” © Sandy Gerrard (CC-BY-SA 2.0); levels and colour enhanced

See also