UK electricity pylon series

Contents

• Overview
• Designations
• Coverage
• Comparisons
• Series list
• 33 and 66 kV
  • Milliken E102
  • Milliken T163
  • Milliken L134
  • Milliken E177
  • Blaw Knox K721
  • Blaw Knox K1373
  • J L Eve C333
  • Blaw Knox K9906
  • L4(m) 66
• 132 kV
  • PL1
  • CS-PL1
  • SS-PL1
  • PL1(c)
  • Rannoch–Abernethy
  • SEE PL1a
  • SEE PL1(b)
  • Tummel–Keith
  • CE PL3
  • PL4/WGR
  • Lydney
  • PL7
  • Blaw Knox K5735
  • PL16
  • Blaw Knox K1420
  • L16/L55
  • Eve 0.175
  • J L Eve C772
  • Inveraray–Taynuilt
  • J L Eve C1415
  • Quoich–Broadford
  • L7
  • L4(m)
• 275 and 400 kV
  • L34
  • L66
  • L2
  • L3
    • Blaw Knox L3
    • J L Eve L3
  • Blaw Knox T2175
  • L6
    • Balfour Beatty L6
    • BICC L6
    • Blaw-Knox L6
    • J L Eve L6
    • L6(c)
    • L6m
  • L8
  • L9
  • L12
  • Coylton–Auchencrosh
  • L13
  • SSE400
  • C-IVI-1

Overview

This page provides a visual overview of most of the major UK electricity pylon (transmission tower) types found within Great Britain; it can be thought of as a kind of “Spotter’s Guide to British Electricity Pylons”. The images are all to scale at 12 pixels per metre. Links are provided to the individual series pages that contain more information.

Where possible, the drawings below are derived from industry material. However, they are all only approximations, as even industry drawings can be inaccurate and at times outright erroneous, and the basis for crossarm lengths is inconsistent (either to the centre of the conductor attachment point or to the end of the steelwork). In some instances, details such as bracing structure is taken from photographs and Google Street View imagery, and some drawings are entirely new work when no drawings are available. Some corrections have been made for apparent and verifiable errors in drawings, but some of these may be incorrect corrections. The drawings are however accurate enough for identification purposes.

The exact design of each tower type also varies, either due to customisation during construction or subsequent modification. Many heavily modified towers exist that do not match any standard design, and terminal and junction towers tend to allow for a variety of crossarm configurations.

As power lines are modified and diverted, old towers are removed and new towers added, and the new towers may be of a completely different series. If the towers on a line appear not to all be from the same series, this is quite likely to be the case.

See the guide page for designation and recognition information.

Designations

Starting with L2 in the 1950s, tower suites have been assigned official designations that are typically taken from their respective specifications (in this case BES L2). Prior to L2 it appears that tower suites never received official designations. The drawings were labelled either with the identity of the power line construction scheme (e.g. SEE PL1(b) or SWE PL16) or with the designer’s contract number (e.g. T2175, C534). The same general design could have multiple designer contract numbers, for example “revised Milliken” (SS-PL1) contract numbers included E112 (NWE PL1), E141 (SWE PL1), E142 (EE PL1) and T161 (CE PL1).

Sometimes a drawing can be in two or more contracts at once. J L Eve L3 Stourport–Ludlow was contract C673, while Beauly–Blackhillock–Kintore was contract C864. The latter contract involved a brand new design of line tower but the angle towers remained unchanged; thus, the C673 drawings were re-used and bear both contract numbers (C673 and C864).

The UK power industry was thus left without any way to refer to tower suites. Repairs and alterations to a line over time mean that individual towers or a portion of a line may be replaced with whatever tower type is current at the time that new towers are constructed. Since these new towers don’t match those used for the rest of the line, some means is needed to refer to their type.

Broadly the industry approach is to refer to a tower suite by the name of its original project where one is known. The CEB/CEGB prefix should be included in this designation but is often omitted. For example, the towers used for the SWE PL16 Andover–Bournemouth–Salisbury line are referred to as “PL16” (formerly “SWE PL16”). Sometimes the designations are ambiguous; the G route tower schedule (Braehead–Greenock) refers to certain S2 towers as type “S.W.E.” referring here not to SWE PL16 but to the SWE PL1(a)&(b) Callender’s type.

There are however a variety of types with no specific name. The 132 kV Eve types in particular resist naming. A batch of UKPN/SPN tower data uses “C534” for Eve’s Zebra conductor type, a suite that is also described as “L16” and in some cases as “L55”. “L132” (see the CEB L132 page) gets used in an confusing manner for types based on that specification and may be used chiefly for Eve towers. Sometimes Eve towers are just described as “J.L.EVE” for want of a proper designation.

Even with L2 onwards there can be confusion. While it was widely understood that L6 existed in multiple versions, the actual set of versions was not correctly known (it is currently believed to be six basic types: the four imperial originals and the two metric types). L3 was more troublesome as it was taken to be Blaw Knox only, with the Eve version largely unknown. There is also the Blaw Knox T2175 derivative in Scotland that originated the L3 DS tower.

In essence, one must be very careful about how one refers to a tower suite. Where possible, include the scheme name in full, e.g. SEE PL7 rather than PL7, to avoid confusion. PL16 is the major exception as it’s a ubiquitous type universally referred to by that name.

The tower nomenclature used on this site is ad hoc in nature to accommodate the lack of available information and due to many series pages having been constructed while it was still commonly believed that the PL codes described tower suites rather than construction contracts.

A few notes:

• There is no such tower type as “PL1”. Tower suites used on PL1 schemes include CS-PL1 (CS PL1, EE PL2), SS-PL1 (SS PL1, SWE PL1, NWE PL1 etc), GEC (SEE PL1(a) and the unconfirmed MEE PL1) and the full Callender’s suite used with SEE PL1(b). PL1b is not synonymous with or the same tower type as PL1.
• Although “PL7” conventionally refers to the Watshams tower suite used for SEE PL7, EE PL3, NWE PL6, NWE PL12, MEE PL9 and so forth, at least one industry employee understood the term “PL7” to refer to a completely different suite, a precursor to PL16 (designed by Blaw Knox), covered here as Blaw Knox K5735. The CEB/CEGB region containing this PL7 scheme is not known nor is the location of any such towers.

Various details below are on the individual series pages remain incorrect and out of date. Corrections will be made over time.

Coverage

Coverage of 132 kV and above is good insofar as indicating which series exist.

Some SL (secondary line, 33 and 66 kV) types are covered, but details are too scarce to permit naming most SL types at this time, and little in the way of schematics has been recovered. 33 and 66 kV types are collected together as the schematics tend not to indicate the design voltage and the phase clearances vary wildly between types.

Comparisons

See the comparisons page.

Series list

This list is not exhaustive.

The earliest known date for each type does not indicate the date that the first line completed construction or was energised: it simply notes the earliest discovered information for the type.

All tower heights below are given primarily in metric for ease of comparison; the original imperial height is appended in brackets for types that originated under imperial measurements.

Dashed outlines for suspension insulators are approximations based on photos that have been added to diagrams that omitted insulator details. These have been added for clarity.

33 and 66 kV

Milliken E102

E102 is an early secondary line type.

Milliken T163

T163 is an early secondary line type.

Milliken L134

L134 is an early secondary line type.

Milliken E177

E177 is a 33 kV type notable for having quad circuit towers.

Blaw Knox K721

K721 is a 66 kV tower series. Depicted in [NSP/004/030]. Blaw Knox is assumed from the K number.

Blaw Knox K1373

K1373 and K4611 “Christmas Tree” towers are a strange type from the mid-1930s. Note that some lines have been upgraded to 132 kV using the existing towers.

Single circuit:

Double circuit, standard types only:

Three-circuit, standard types only:

J L Eve C333

J L Eve C333 is a 33 kV tower series.

Blaw Knox K9906

Blaw Knox K9906 is a 66 kV tower series. Known examples are currently running at 33 kV.

L4(m) 66

L4(m) 66 is an adaptation of L4(m) for 66 kV.

132 kV

PL1

See:

• CS-PL1
• SS-PL1
• SEE PL1(a)
• SEE PL1(b)
• PL4 (WGR PL1)

CS-PL1

CS-PL1 (“original Milliken”) was the first Milliken design for the UK. It is known from CS PL1 and SEE PL2.

Single circuit:

Double circuit:

SS-PL1

SS-PL1 (“revised Milliken”) was the second Milliken design for the UK. It was used for most of the original PL1 schemes including SS PL1, EE PL1, SWE PL1 and NWE PL1. Amongst the various differences between SS-PL1 and CS-PL1, the most noticeable is that the peak of line towers contains bracing.

Callenders designed at least one tower type designated SWE PL1(a)&(b); this is an S2 type used in conjunction with Milliken SS-PL1 angle towers.

Single circuit:

Double circuit:

PL1(c)

See under SS-PL1.

Rannoch–Abernethy

The so-called “Grampian pylons” appear to be specific to a single line in Scotland.

Double circuit 132 kV:

Double circuit 132 kV plus double circuit 33 kV:

SEE PL1a

SEE PL1a is a slimmer design than the Milliken towers; the designer is taken to be GEC (listed seemingly incorrectly in the Tower Bible as Pirelli). Not to be confused with the unrelated Callender’s type SWE PL1(a)&(b) (see under SS-PL1 above). This type was also used for the Mid-East England region, presumed to be scheme MEE PL1.

SEE PL1(b)

SEE PL1(b) is a Callender’s type. Not to be confused with the unrelated type SWE PL1(a)&(b) (see under SS-PL1 above).

Tummel–Keith

Tummel–Keith is a type known only from a former line between Tummel Bridge and Keith, Scotland, constructed circa 1936–1939.

Original dual voltage towers:

Uprated 132 kV double circuit towers:

CE PL3

CE PL3 appears to be the precursor to CE PL4.

Blaw Knox CE PL3 is similar to CE PL4 and appears to be a short-lived, older design without proper earthwire peaks on the angle towers. Single and double circuit.

PL4/WGR

The PL4 line tower is remarkably similar to that of PL16. The top crossarm of PL4 D2 is roughly the same height as the other crossarms, while PL16’s top crossarm is distinctly taller than the rest.

PL4 is notable for its double earthwire type having an extra crossarm at the top, instead of the combination phase/earth crossarm arrangement of PL7 and PL16.

This design is assumed to have originated with contract CE PL4. This design was subsequently used during World War II for the Wartime Grid Reinforcement (or War Time Grid) schemes, gaining it the name “WGR”.

Lydney

“Lydney” is a temporary designation for the 132 kV towers found at Lydney in Gloucestershire, England. This seems to be a Blaw Knox design based on its similarity to CE PL4.

PL7

PL7 D2 is quite similar to that of L16/L55, again with open crossarms, and the DD2 type could be confused with PL16 DD2.

The 132 kV Watshams suite that appears to have originated as SEE PL7 was also used (at least in part) for: EE PL3; NWE PL6; MEE PL9, PL12 and PL13; SWE PL10 and PL11.

Blaw Knox K5735

Blaw Knox K5735 is a tower type of which very little is known. Allegedly it was used by a PL7 scheme somewhere. It appears to be the precursor of PL16.

PL16

PL16 contains more than one design for the D2 and DD2 towers; the known variants are SWE and “Scottish” (both Blaw Knox). The remainder of the tower types appear to have only a single design. The “Scottish”-style D2 towers bear some resemblance to the PL1 family and PL4. The “Scottish” D2 types appear to be widespread in England, while the SWE D2 type can be found in Scotland!

In Scotland, these towers were constructed to specification STL1. STL1 contains double and single circuit (including single circuit double earthwire) and flat formation single circuit towers with no earthwire. SWE PL16 single circuit remains unconfirmed. “PL16” is now a catch-all classification within the UK power industry of uncertain scope, which may or may not (depending on your source) include non-Lynx towers. The “Scottish” towers refer to STL1. STL1 D2 became PL16 D2S (also “D2(S)”).

Blaw Knox K1420

Blaw Knox K1420 is a suite of flat formation towers. There is no known line tower. Wood poles are used for intermediates instead.

Associated intermediates:

L16/L55

L16 and L55 are designations applied to what appears to be a single J L Eve tower series. Eve appeared not to use series designations and it seems likely that L16 and L55 are both external designations for the same series. The design is similar to SWE PL16, but the crossarms are open instead of braced. “L132” appears to be another designation that is applied to these towers.

J L Eve drawing C534/273C (JE35/35693) demonstrates that the DT/DT90 tower is highly customisable according to requirements, hence the variations observed above. These variations are likely not official types but examples of adaptation according to specific requirements at each substation and cable sealing end.

Eve 0.175

Eve 0.175 is similar to L16 but was designed for 0.175^□″ SCA conductors—the same as PL16—instead of the 0.4^□″ SCA conductors of L16. No official designation is known.

Strengthened towers on the line between Nairn and Keith, Scotland:

J L Eve C772

J L Eve C772 is a very small tower type designed for 0.125^□″ SCA conductors.

Inveraray–Taynuilt

The towers used for Inveraray–Taynuilt may be a derivative of Eve C772 but no details are known.

J L Eve C1415

J L Eve C1415 is a very small tower type designed for 0.125^□″ SCA conductors. It is a revision of Eve C772.

Quoich–Broadford

The tower type used for Quoich–Broadford is a derivative of the type used for Inveraray–Taynuilt; no details are known.

L7

L7 is a higher-capacity 132 kV type: unlike other 132 kV types, L7 supports twin conductor bundles. L7 is used for replacement towers on L16 lines due to its ability to take the heavier conductors.

L4(m)

L4(m) is distinctive for its use of open, nearly isosceles crossarms instead of the conventional right triangle shape; this arrangement can also be found on the much larger 400 kV L12 and SSE400 types. D60 and D90 bear a horizontal projection at the top for the earth wire.

The bracing in red in the D60 diagram represents how D60 towers appear in reality; possibly it was mistakenly omitted from the diagram, or the design could have changed.

Although not known from any official material, there are also specially-adapted single-circuit towers. The formal designations are not known, and the diagrams depict simply the visual changes:

275 and 400 kV

L34

L34 is a flat single-circuit 275 kV type.

L66

L66 is a rare type similar to L2 and L3.

L2

L2 towers take twin conductor bundles and operate at 275 kV or 400 kV. Contrast the smaller L3 below. The T1648 line tower is included here as it was used in conjunction with L2 angle towers.

L3

Blaw Knox L3 is a scaled-down, 275 kV–only version of L2. As with L2, it is twin conductor, but designed for 0.175^□″ instead of 0.4^□″ conductors. There is also an Eve version of L3.

Blaw Knox L3

J L Eve L3

Blaw Knox T2175

Blaw Knox T2175 is a derivative of L3.

L6

L6 appears to be the joint tallest series in the UK along with SSE400. L6 towers are reported to have been instigated to allow quad conductor bundles (four cables strung from each crossarm), and this extra cable weight necessitated taller and stronger towers than L2.

Balfour Beatty L6

BICC L6

SF60 omitted due to chart errors.

Some towers were re-used in L6(c) below.

Reduced-height, “headless” towers can be found at Dungeness; the drawing below is approximate due to the lack of a good BICC L6 chart:

Blaw-Knox L6

J L Eve L6

Some drawings pending chart availability. Some towers were re-used in L6(c) below.

L6(c)

L6m

L8

L8 is a 275 kV and 400 kV tower series. Standard 400 kV towers:

Smaller 275 kV towers:

Like L4, L8 has been adapted into single-circuit form; as with L4, the designations are not known and those given below are only suggestions:

L9

L9 is a low-height series, specifically the low-height version of L6. L9 is very similar to L12 low-height, but L9 towers suspend the cables from pairs of insulator strings in a V formation, while L12 uses simple suspension insulators.

L12

L12 is the other well-known series with near-isosceles crossarms (shared by the L12-derived SSE400). L12 however has braced crossarms and is vastly larger than L4. Note the lower deviation angles of D25 and D55 compared to the convention of D30 and D60. L12 standard height:

L12 low height:

Coylton–Auchencrosh

Coylton–Auchencrosh is a custom type used for a single line in Scotland.

L13

L13 is another replacement for L6. Information on L13 is incomplete and contradictory.

SSE400

SSE400 is a 400 kV type derived from L12 designed for the Beauly–Denny line across the Scottish highlands.

C-IVI-1

C-IVI-1 (also CIVI-1) is a single circuit 400 kV type.