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PL4/WGR

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Overview

PL4 is a UK electricity pylon (steel lattice transmission tower) series. PL4 is one of only a few series to support double earthwires, doing so with separate earthwire crossarms. PL4 appears to be a revision of CE PL3 that added extra clearance to the earthwire (or earthwires in the case of double earthwire towers).

The towers were designed for scheme CE (Central England) PL4. The name has been simplified to “PL4” as it has been used for later schemes across the UK. The series is also known as “WGR” (Wartime Grid Reinforcement) as it was used for various new lines constructed during World War II.

General data

Contractor Blaw Knox
Found United Kingdom
Height (straight line tower) 86′–0″ (26.2 m)
91′–3″ (27.8 m) (double earth)
Voltage 132 kV
Dates back to 1936–37 (drawings)
Design conductor 0.175″ SCA (now 175 mm² Lynx ACSR)
Known heights STD
E5 (+5′) (only listed for D2)
E10 (+10′)
E20 (+20′)
E30 (+30′) (not listed for D30)
E20+10′ (+30′) (only listed for D10)
Circuit count Single, double

E20+10′ denotes an E20 extension plus another 10′ extension for a total of 30′ extra height, rather than a separate design as with the normal E30.

WGR

[Standard Tower Types] refers to this design as “WGR (or PL4)”. This reflects the fact that the design was adopted for the Wartime Grid Reinforcement (or War Time Grid) schemes. The Wartime Grid Reinforcement accounts for these towers being found outside of the CE region. Scheme WGR PL1 is the V route from Harker to Galashiels; this is the only WGR scheme identified by name at present, but quite a few were constructed across the UK.

The drawing schedule for WGR lists numerous drawing ranges; without examining a sample of each range it’s not possible to determine what each range represents.

Contract XM range Description Usage
K1611 XM1276 CE PL3 Various details, single and double circuit; general arrangement drawings for S2, S10, S30 and S60
K1857 XM1317 CE PL4 Various, including general arrangement and erection diagrams for double circuit towers
K2231 ? ? Various details, double circuit only
K2737 ? ? Various details, including single circuit towers
K5297 ? ? Various details, including erection diagrams for single circuit towers
? XM1363 ? Various general arrangement drawings
? XM1425 ? Various (double circuit)
? XM1525‡ ? Various (double circuit)
? XM1692 ? General arrangement drawings for single circuit towers; possibly K5297
K5784 XM1746 War Time Grid Various details
? XM1857 ? Erection diagram for 20 foot extension, D10/DD10

‡ With only one known drawing, one would think that this is a typing mistake for XM1425 but the large leap in BK35 numbering makes it impossible to be sure.

Can be confused with

Lines

Various lines have been found to date. A few are confirmed and detailed below:

Double-circuit lines confirmed so far:

Tower forms

The K5784 War Time Grid Reinforcement drawing schedule includes both single and double circuit towers. Single-circuit WGR lines have yet to be identified however.

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

Single circuit

PL4 S2
PL4 S30
PL4 S60
PL4? S90?

The single-circuit diagrams above are based primarily on the line from Bridgwater to Taunton, which is primarily SWE PL1(a)&(b) but the last stretch is a revised form of CE PL3 that is almost certainly PL4. The line tower diagram is cloned from CE PL3 as it appears to be identical.

LSTC gave the S60 tower as “PL9” when drawing up material for line alterations for a new housing estate in Staplegrove; this designation has not been explained.

An S60 tower can also be found at Cargenbridge, near Dumfries. This is listed on the tower schedule as type “NWE”. No such NWE line has yet been identified.

The tower suggested to be an S90 can be found outside Taunton substation, carrying an 84° deviation; this is the least accurate due to the lack of good viewing angles from Google Street View. There is no visual reason why this would be PL4 and not K1201; the other angle towers differ in crossarm bracing between PL3/PL4 and K1201.

Double circuit

CE PL4 D2
CE PL4 DD2
CE PL4 D10
CE PL4 DD10
CE PL4 D30
CE PL4 DD30
CE PL4 D60
CE PL4 DD60
CE PL4 D90
CE PL4 DD90
CE PL4 DDT90 “A”
CE PL4 DDT90 “B”
PL4 DDT90 variant 1
PL4 DDT90 variant 2

Details on the terminal towers are unclear. CEA drawing ED51147 names the type as “D.D.T.90°.TOWER” but specifically shows the tower without auxiliary crossarms (omitted from the side view). Variants “A” and “B” are depicted as per drawing ED51147, without auxiliary crossarms. However, there most certainly are PL4 DDT90 towers with auxiliary crossarms. Variant 1 above is depicted with a preliminary depiction of the auxiliary crossarms as seen on a WGR tower at Upper Boat Substation, South Wales (between Pontypridd and Treforest Industrial Estate, 51.576° N 3.297° W). The next tower is a DD60 (51.576° N 3.294° W), after which the line changes to PL16. DDT90 variant 2 depicts the WGR tower found in Watford, Hertfordshire, England (see links below) with a longer middle auxiliary crossarm. There is also a terminal tower at Blackburn Substation (see links below) without auxiliary crossarms that would better fit the description of DDT.

ED51147 was drawn on 18/12/1956 and originally covered only a single design. Variant “B” was added on a date that one would presume says “7·5·58” (because “7·5·56” would make no sense as an amendment); this second variant represents a tower used in or at “Sundon”, presumably Sundon Substation, a tower that appears to no longer exist. Variant B is simply Variant A without the extended length top crossarms; the remainder of the tower is identical.

Tower details

Crossarm width is the total width across the widest crossarm.

Type Source Height Base width Crossarm width
CE PL4 D2 K1857-8F 86′–0″ (26.2 m) 16′–0 (4.9 m) 32′–0″ (9.8 m)
CE PL4 DD2 ED51108 (Tower Bible) 91′–3″ (27.8 m) 16′–018″ (4.9 m) 32′–0″ (9.8 m)
CE PL4 D10 ED51114 (Tower Bible) 84′–9″ (25.8 m) 18′–0″ (5.5 m) 29′–6″ (9.0 m)
CE PL4 DD10 ED51116 (Tower Bible) 88′–3″ (26.9 m) 18′–0″ (5.5 m) 29′–6″ (9.0 m)
CE PL4 D30 ED51121 (Tower Bible) 84′–3″ (25.7 m) 22′–0″ (6.7 m) 32′–0″ (9.8 m)
CE PL4 DD30 ED51124 (Tower Bible) 87′–9″ (26.7 m) 22′–0¼″ (6.7 m) 32′–0″ (9.8 m)
CE PL4 D60 ED51130 (Tower Bible) 85′–9″ (26.1 m) 23′–0″ (7.0 m) 33′–6″ (10.2 m)
CE PL4 DD60 ED51134 (Tower Bible) 89′–3″ (27.2 m) 23′–0″ (7.0 m) 33′–6″ (10.2 m)
CE PL4 D90 ED51138 (Tower Bible) 85′–9″ (26.1 m) 23′–0″ (7.0 m) 38′–6″ (11.7 m)
CE PL4 DD90 ED51141 (Tower Bible) 89′–3″ (27.2 m) 23′–0″ (7.0 m) 38′–6″ (11.7 m)
CE PL4 DDT90 ED51147 (Tower Bible) 89′–3″ (27.2 m) 23′–0″ (7.0 m) 50′–0″ (15.2 m)

See also