UK electricity pylon series

Contents

• Overview
  • Designations
  • Coverage
  • Comparisons
• Series list
• 33 and 66 kV
  • Milliken L134
  • Milliken E102
  • Milliken T163
  • SEE SL2
  • Blaw Knox K721
  • SEE SL3
  • J L Eve C15
  • Milliken E177
  • SEE SL4
  • NWE SL7
  • SEE SL8
  • Blaw Knox K1373 and K4611
  • NWE SL4
  • J L Eve C333
  • Abergavenny and Cwmbran
  • Blaw Knox K8790
  • Blaw Knox K9906
  • L4(m) 66
• 110 kV
  • Belfast four-circuit
  • Blaw Knox K1641
• 132 kV
  • PL1
  • CS-PL1
  • SS-PL1
  • NWE PL2
  • PL1(c)
  • Rannoch–Abernethy
  • SEE PL1a
  • SEE PL1(b)
  • Spey Valley Extension
  • CE PL3
  • PL4/WGR
  • Lydney
  • PL7
  • Blaw Knox K5735
  • PL16
  • Blaw Knox K1201
  • Blaw Knox K1420
  • J L Eve C534 (L16, Eve 0.4)
  • J L Eve C670 (Eve 0.175)
  • J L Eve C772
  • Inveraray–Taynuilt
  • J L Eve C1415
  • Quoich–Broadford
  • L7
  • L4(m)
• 275 and 400 kV
  • L34
  • L66/89
  • L2
  • L3
    • Blaw Knox L3
    • J L Eve L3
  • Blaw Knox T1521
  • Blaw Knox T1648
  • 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 the UK. 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: even industry drawings can be inaccurate and at times outright erroneous. 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.

Actual towers may differ from the diagrams here due to enhancements to the design, customisation during construction or subsequent modification (especially strengthening). 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 that are not all covered here.

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 to the remainder of the line. If the towers on a line appear not to all be from the same series, this is quite likely to be the case.

Designations

The series names used on this site are not all official; some have been devised solely for convenience in order to give the tower suite a name within this website. See the guide page for recognition information and more detailed information on tower series designations.

Coverage

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

Coverage of 33 and 66 kV remains low due to the limited amount of material recovered; it appears that there are over 30 separate 33 and 66 kV tower suites, but at present there is not enough information to draw them all to scale. 33 and 66 kV types are collected together as the schematics tend not to indicate the design voltage and the phase and ground clearances overlap between the two voltages.

See the project completeness page for more details on progress to date and the material and details still required in order to achieve complete coverage.

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, such as the oldest date found on a drawing or the year of the specification.

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.

Location flags are only shown for types where it’s reasonably certain what countries they can be found in. A lack of flags indicates uncertainty, not extinct types: extinction is shown instead using faded flags. Locations in brackets denote where towers are found only as a substitute and not used for complete lines.

Series	Found	Voltage	Height (line tower)	Earliest known date	Designer
Milliken L134		66 kV	20.3 m (66′–6″)	1927	Milliken Brothers
CS-PL1		132 kV	20.2 m (66′–3″) (S2) 23.9 m (78′–3″) (D2)	1928	Milliken Brothers
Milliken E102			14.2 m (46′–6″) (S3)	1929	Milliken Brothers
Milliken T163			18.5 m (60′–9″) (D3)	1929	Milliken Brothers
SEE PL1a	()	132 kV	24.0 m (78′–9″) (D2) 20.3 m (66′–9″) (S2)	1929	GEC/Pirelli-General
SEE PL1(b)		132 kV	23.5 m (77′–0″) (D2) 19.8 m (65′–0″) (S2)	1929	Callender’s
SEE SL2		33 kV		1929	Watsham’s
NWE PL2		132 kV	?	1930	Milliken Brothers
Blaw Knox K721		66 kV		1930	Blaw Knox
SEE SL3		33 kV	48′–9″ (14.9 m) (D3) 42′–9″ (13.0 m) (S3)	1930	Watsham’s
Rannoch–Abernethy		2 × 132 kV 2 × 132 kV + 2 × 33 kV		ca. 1930	?
J L Eve C15		66 kV	15.7 m (51′–5¾″) (0.1″ SCA) 15.3 m (50′–1″) (0.15″ SCA)	1930	J L Eve
SS-PL1		132 kV	20.3 m (66′–9″) (SS PL1 S2) 24.2 m (79′–3″) (EE PL1 D2)	1931	Milliken Brothers
Milliken E177		33 kV	19.2 m (62′–11″) (double circuit) 22.6 m (74′–0″) (quad circuit)	1932	Milliken Brothers
Belfast four-circuit		2 × 110 kV + 2 × 33 kV		1932	Callender’s
SEE SL4			?	1934	Watsham’s
NWE SL7		?	?	?	Watsham’s
SEE SL8		33 kV	?	?	Watsham’s
NWE SL4		66 kV	21.0 m (68′–9″)	1935	Blaw Knox
Spey Valley		132 kV + 33 kV	24.8 m (81′–4″)	1936	Blaw Knox
Blaw Knox K1373		2 × 66 kV 2 × 66 kV + 1 × 33 kV 2 × 132 kV	23.5 m (77′–0″) (type A) double-circuit line tower 23.2 m (76′–0″) (type S three-circuit line tower)	1936	Blaw Knox
CE PL3		132 kV		1936	Blaw Knox
PL4/WGR		132 kV	26.2 m (86′–0″)	1936	Blaw Knox
J L Eve C333		33 kV	18.1 m (59′–6″)		J L Eve
Abergavenny/Cwmbran		66 kV	?	?	?
Lydney		132 kV			Blaw Knox?
PL7		132 kV	26.76 m (87′–95⁄8″)	1938	Watsham’s
Blaw Knox K5735		132 kV	27.4 m (89′–9″) (DD2)	1940	Blaw Knox
PL16		132 kV	26.4 m (86′–9″) (D2) 26.3 m (86′–3″) (D2S)	1944	Blaw Knox
Blaw Knox K8790		66 kV	?	1945	Blaw Knox
Blaw Knox K1201	( )	132 kV	22.6 m (74′–3″)	1947	Blaw Knox
Blaw Knox K1420	)	132 kV	13.0 m (42′–6″) (S10)	1947	Blaw Knox
Blaw Knox K9906		66 kV	19.8 m (65′–0″)	1947	Blaw Knox
J L Eve C534		132 kV	27.1 m (88′–10″)	1950	J L Eve
L34		275 kV	25.9 m (85′–0″)	1950	Milliken or Blaw Knox
L66/L89		275 kV	34.3 m (115′–3″)	1950–52	Blaw Knox
L2		275 kV/380 kV/400 kV	41.6 m (136′–6″)	1952	Blaw Knox
J L Eve C670		132 kV	26.1 m (85′–8″)	1946/1953	J L Eve
L3		275 kV	36.9 m (121′–0″) (Blaw Knox D) 36.1 m (118′–3½″) (J L Eve D, C673) 38.1 m (125′–0″) (Blaw Knox DS) 38.0 m (124′–9″) (J L Eve D, C864)	1953	Blaw Knox, J L Eve
J L Eve C772		132 kV		1957	J L Eve
Inveraray–Taynuilt		132 kV		1959	?
L6		400 kV	ca. 50 m (varies)	1960	Balfour Beatty, BICC, Blaw Knox, J L Eve
Blaw Knox T1521		275 kV	38.1 m (125′–0″)	1960	Blaw Knox
Blaw Knox T1648		275 kV/380 kV	44.0 m (144′–3″)	1961	Blaw Knox
L7	…	132 kV	26.9 m	1963	BICC and J L Eve
L8	()	400 kV, 275 kV	46.4 m (400 kV) ca. 40 m (275 kV)	1966	Blaw Knox
L9		400 kV	31.7 m (104′–0″)	1966	J L Eve
Blaw Knox T2175		275 kV	38.1 m (125′–0″)	1967	Blaw Knox
J L Eve C1415		132 kV	22.3 m (73′–3″)	1970	J L Eve
L4(m)		132 kV	26.1 m	1972	Blaw Knox
Quoich–Broadford		132 kV	22.4 m (73′–6″)	1975	Blaw Knox
L12		400 kV	46.5 m (standard height) 35.3 m (low height)	1984	?
L4(m) 66		66 kV	?	?	Blaw Knox
Coylton–Auchencrosh		275 kV	25.2 m	1992/2001	Balfour Beatty
L13		400 kV	49.95 m		Babcock
SSE400		400 kV	50.5 m		Balfour Beatty
C-IVI-1	–	400 kV	32 m		ESB International

Dashed outlines for suspension insulators are approximations only, added for clarity.

33 and 66 kV

Milliken L134

L134 is a 66 kV type that appears to slightly pre-date the national grid, designed for the power line from Maentwrog hydroelectric power station to Crewe via Legacy substation.

Milliken E102

E102 is an early secondary line type, designed for the SEE and MEE regions.

Milliken T163

T163 is an early secondary line type, used by the NWE SL2 contract.

SEE SL2

SEE SL2 refers to the towers used on the SEE SL2 33 kV contract; currently it is being grouped under SL2 until we know whether these two types differed in any visible way.

Blaw Knox K721

K721 is a 66 kV tower series. The origin of the type is a mystery; it was also used in the north-east of England, where it can still be found.

SEE SL3

SEE SL3 refers to the towers used on the SEE SL3 33 kV contract. The type given in Marshall 1933 is included as it seems to be all but identical; this type is used to fill in gaps left by unrecovered SEE SL3 drawings. Only one drawing has been recovered for SEE SL2 (D60/DT) and it is identical (above ground) to SEE SL3 D60, suggesting that SEE SL2 and SL3 may be indistinguishable. SEE SL2 is covered under SEE SL3 for now.

J L Eve C15

C15 (also numbered C23) comprises two 66 kV tower sub-series, both designed for the joint NEE SL1–MEE SL2 contract.

J L Eve C15 0.1^□″ SCA type:

J L Eve C15 0.15^□″ SCA type:

Milliken E177

E177 is a 33 kV type notable for having quad circuit towers. This type appears to have been designed for the Wiltshire and Hampshire area, contract SWE SL2 and apparently (not verified) also SWE SL3

SEE SL4

SEE SL4 refers to the towers used on the SEE SL4 contract, taken to be 33 kV. Drawings for the line towers have not been recovered, nor have D30, S60 and ST.

NWE SL7

NWE SL7 refers here to towers used for the NWE SL7 contract. No material has been recovered and the originating contract for the remainder of the towers is unconfirmed. The towers are related to those of SEE SL8.

SEE SL8

SEE SL8 refers here to towers currently assumed to have been designed for the SEE SL8 33 kV contract. Only the terminal tower drawing has been recovered so far; these terminal towers can also be seen on other lines either side of undergrounded section of line. The originating contract for the remainder of the towers is unconfirmed. The towers are related to those of NWE SL7.

Blaw Knox K1373 and K4611

K1373 and K4611 “Christmas Tree” towers are a strange type from the mid-1930s designed for the MIDESCO lines in Derbyshire, Nottinghamshire and Leicestershire. Note that some lines have been upgraded to 132 kV using the existing towers, while the rest have been de-rated to 33 kV or demolished.

Single circuit:

Double circuit, standard types only:

Three-circuit, standard types only:

NWE SL4

NWE SL4 refers to towers used on the NWE SL4 66 kV contract, designed by Milliken Brothers.

J L Eve C333

J L Eve C333 is a 33 kV tower series, used for contracts SWE SL9 (33 kV line from Bath to Melksham) and SWE SL10.

Abergavenny and Cwmbran

Abergavenny/Cwmbran is a 66 kV tower series possibly derived from C333. It is found on a line in Abergavenny and two in nearly Cymbran, South Wales.

Blaw Knox K8790

Blaw Knox K8790 is a 66 kV tower series, seemingly designed for Preston Corporation. Known examples are currently running at 33 kV. Presently there are no expectations of access to any drawings and the diagrams below are just everything found on the set of related lines (drawn to an estimated scale), regardless of what tower suite they originated from, as details are so scarce.

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, seemingly for the purpose of replacing older towers.

110 kV

Belfast four-circuit

Callender’s four-circuit type likely specific to Belfast; ca. 1932.

Blaw Knox K1641

Blaw Knox K1641 is, if understood correctly, a suite of single-circuit, flat formation lattice towers designed for deviation and termination of wood pole lines.

132 kV

PL1

See:

• CS-PL1
• SS-PL1
• SEE PL1a
• SEE PL1(b)
• PL4 (WGR PL1)

CS-PL1

CS-PL1 (“original Milliken”) was the first Milliken Brothers 132 kV design for the UK (L132 66 kV appears to be marginally older). It is known from contracts CS PL1 and SEE PL2.

Single circuit:

Double circuit:

SS-PL1

SS-PL1 (“revised Milliken”) was the second Milliken 132 kV design for the UK. It was used for most of the original PL1 contracts including SS PL1, EE PL1, SWE PL1 and NWE PL1. Amongst the various differences between SS-PL1 and CS-PL1, the most noticeable is the additional of bracing to the line tower peak.

SWE PL1 used a Callender’s S2 tower; the remainder of the tower types were of the Milliken type.

Single circuit:

Double circuit:

NWE PL2

Contract NWE PL2 contains special towers for NWE PL1.

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

Contracts SEE PL1a and MEE PL1 used a slimmer design than the contemporary Milliken towers, designed by a group led by GEC. This type was also used for Mid-East England (MEE) contract PL1.

SEE PL1(b)

Contract SEE PL1(b) used a Callender’s type.

Spey Valley Extension

Blaw Knox K1576 covered the towers for the Spey Valley Extension in Scotland, constructed circa 1936–1939 between Tummel Bridge and Keith.

Original dual voltage towers:

Uprated 132 kV double circuit towers:

CE PL3

CE PL3 refers to what appears to be the short-lived precursor to the towers used for contract CE PL4. Very few PL3 drawings have been recovered, and very few PL3 lines ever existed.

PL4/WGR

PL4 is a tower suite created for contract CE PL4, subsequently used during World War II for the Wartime Grid Reinforcement (or War Time Grid) contracts, gaining it the alternative name “WGR”. 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.

Modified line towers, Barrow-in-Furness:

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

The PL7 tower suite is a type believed to have originated with contract SWE PL7. It was also used (in whole or in part) for contracts EE PL3; NWE PL6; MEE PL9, PL12 and PL13; SWE PL10 and PL11.

Blaw Knox K5735

Blaw Knox K5735 appears to have been designed for the line between Preston and Thornton-Cleveleys, since demolished. National Grid understood it to be “PL7”, which suggests that the line it was designed for was contract NWE PL7, still pending confirmation. It is an evolutionary step between PL4/WGR and PL16.

PL16

PL16 was designed for (and named after) the SWE PL16 contract, Andover to Bournemouth via Salisbury. It was adopted as the UK’s standard 132 kV single Lynx type between the 1940s and the 1970s, when it was superseded by L4(m). Most PL16 lines use the revised line towers designed for NoSHEB in Scotland as part of contract K9857 (designated D2S and DD2S outside of NoSHEB), while the original line towers can also be found in Scotland. The exact scope of the term “PL16” is hopelessly unclear.

Classed as PL16 for now:

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

Blaw Knox K1201

Blaw Knox K1201 is a single-circuit companion suite to K9857 designed for Scotland.

Strengthened towers:

Blaw Knox K1420

Blaw Knox K1420 is a suite of single circuit towers; orignally designed for NoSHEB, they were also adopted for use in England and Wales, but not Northern Ireland where a different type was selected for the same purpose. The line tower is triangular formation and is not used on most lines; wood pole intermediates are typically used instead. The angle towers are flat formation.

Example associated wood pole intermediates:

J L Eve C534 (L16, Eve 0.4)

J L Eve C534 is Eve’s single Zebra 132 kV tower suite.

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.

J L Eve C670 (Eve 0.175)

J L Eve C670 is similar to C534 but was designed for 0.175^□″ SCA conductors—the same as PL16—instead of the 0.4^□″ SCA conductors of C534. It appears that the line towers were designed first (for Tummel–Garry) as C432 in 1946, and the remainder of the type as C670 in 1953.

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

J L Eve C772

J L Eve C772 is a light construction type designed for 0.125^□″ SCA conductors, for the line between Clachan and Carradale, Scotland. See also C1415.

Inveraray–Taynuilt

Blaw Knox T1498 is a light construction type designed for 0.125^□″ SCA conductors, for the line between Inveraray and Taynuilt, Scotland.

J L Eve C1415

J L Eve C1415 is a light construction type designed for 0.125^□″ SCA conductors. It is a derivative of Eve C772. The recovered drawings are mostly C1824 which appears to be metricated C1415.

Quoich–Broadford

The tower type used for Blaw Knox T2639 is a light construction type designed for 0.125^□″ SCA conductors, for the line between Quoich (mainland Scotland) and Broadford (Skye). It is derived from the Inveraray–Taynuilt type (Blaw Knox T1498).

L7

L7 is a higher-capacity 132 kV type: unlike other 132 kV types, L7 supports twin Lynx 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.

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.

L66/89

L66/89 is the precursor 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 T1521

Blaw Knox T1521 may just be a contract for an enhanced L3 line tower.

Blaw Knox T1648

Blaw Knox T1648 may just be a contract for an enhanced L2 line tower.

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(m), L8 has been adapted into single-circuit form, with the series name “L8(c) Modified”:

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.