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UK electricity pylon series

Contents

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:

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.

SL (secondary line) towers are all but ignored for now as no means has been found to refer to them in a sensible and unambiguous manner. No SL types are known to have an official designation and some were given multiple contract numbers.

Comparisons

See the comparisons page.

Series list

This is a list of most known series; 33 kV is not covered, nor is all of 66 kV. Not all 132 kV is included either.

Earliest known date 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.

Series Voltage Conductors Height (D/D2) Earliest known date Designer
CS-PL1 132 kV Single 1928 Milliken
SS-PL1 132 kV Single 1931 Milliken
SEE PL1a 132 kV Single 1929 GEC?
SEE PL1(b) 132 kV Single 1929 Callender’s
Blaw Knox K721 66 kV 1930 Blaw Knox
Rannoch–Abernethy 2 × 132 kV
2 × 132 kV + 2 × 33 kV
Single ca. 1930 ?
Tummel–Keith 132 kV Single ca. 1930–1939 ?
Blaw Knox K1373 2 × 66 kV
2 × 66 kV + 1 × 33 kV
2 × 132 kV
Single 77′–0″ (23.5 m) (type A) double-circuit line tower
76′–0″ (23.2 m) (type S three-circuit line tower)
1936 Blaw Knox
CE PL3 132 kV Single 1936 Blaw-Knox
PL4/WGR 132 kV Single 26.2 m (86′–0″) 1936 Blaw-Knox
Lydney 132 kV Single Blaw-Knox?
PL7 132 kV Single 26.76 m (87′–958″) 1938 Watshams
Blaw Knox K5735 132 kV Single 27.4 m (89′–9″) (DD2) 1941 Blaw Knox
PL16 132 kV Single 26.4 m (86′–9″) (D2)
26.3 m (86′–3″) (D2S)
1944 Blaw-Knox
L16/L55 132 kV Single 27.1 m (88′–10″) J L Eve
Eve 0.175 132 kV Single 85′–8″ (26.1 m) J L Eve
Blaw Knox K9906 66 kV 1947 Blaw Knox
L34 275 kV Twin 25.9 m (85′–0″) 1950 Milliken or Blaw-Knox
PB 132 kV ca. 1950s Painter Brothers?
L66 275 kV Twin 34.3 m (115′–3″) Blaw-Knox
L2 275 kV/380 kV/400 kV Twin 41.6 m (136′–6″) 1952 Blaw-Knox
L3 275 kV Twin 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
L6 400 kV Triple, quad ca. 50 m (varies) 1960 Balfour Beatty, BICC, Blaw-Knox, J L Eve
L7 132 kV Single, twin 26.9 m BICC and J L Eve
Eve C772 132 kV Single 1957 J L Eve
Inveraray–Taynuilt 132 kV Single ?
Blaw Knox T2175 275 kV Single 38.1 m (125′–0″) 1967 Blaw-Knox
Eve C1415 132 kV Single 1970 J L Eve
Quoich–Broadford 132 kV Single ?
L4(m) 132 kV, 66 kV Single 26.1 m 1975 Blaw-Knox
L8 400 kV, 275 kV Twin 46.4 m (400 kV)
ca. 40 m (275 kV)
Blaw-Knox
L9 400 kV Quad 31.7 m (104′–0″) ?
L12 46.5 m (standard height)
35.3 m (low height)
?
L13 400 kV 49.95 m Babcock
SSE400 400 kV Twin 50.5 m Balfour Beatty

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 kV

One day maybe.

66 kV

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 K9906

K9906 is a 66 kV tower series. Depicted in [NSP/004/030].

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:

K4611? line SEW
K4611? line DEW
K4611? angle SEW
K4611? angle DEW

Double circuit, standard types only:

K1373 A SEW
K1373 A DEW
K1373 A special DEW
K1373 A (no EW crossarm)
K1373 A (85° EW swing)
K1373 B SEW
K1373 B DEW
K4611 DB SEW
K4611 DC SEW, 132 kV
K4611 DB DEW
K4611 DC DEW, 132 kV
K1373 B transposition
K1373 B transposition
K1373 C
K4611 DC SEW
K4611 DC DEW
K1373 C terminal (symmetric)
K1373 C terminal (asymmetric)

Three-circuit, standard types only:

K1373 S SEW
K1373 S DEW
K1373 S 33 kV–only transposition SEW
K1373 S 33 kV–only transposition DEW
K1373 M SEW
K1373 M DEW
K1373 M transposition
K1373 M (four-tier)
K1373 D SEW
K1373 D DEW
K1373 D terminal

132 kV

PL1

See:

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:

CS PL1 A1 / S2
CS PL1 B1 / S10
CS PL1 C1 / S30
CS PL1 D1 / S60/ST

Double circuit:

CS PL1 A2 / D2
CS PL1 A3 / D30
CS PL1 A4 / D60/DT

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:

CE PL1 S2 (Milliken)
SS PL1 S2 (Milliken)
SWE PL1(a)&(b) S2 (Callender’s)
SS PL1 S10
PL1(c) S10

Double circuit:

EE PL1 D2
SWE PL1 D2
SWE PL1 D10
EE PL1 D30
EE PL1 D60
SWE PL1 D60
EE PL1 DT
SWE PL1 DT
SWE PL1 DT60
SWE PL1 DT-type Junction
EE PL1 DT90
SS-PL1 PL1 transposition tower

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:

Line tower, double circuit
Angle tower 1, double circuit
Angle tower 2, double circuit
Transposition tower, double circuit

Double circuit 132 kV plus double circuit 33 kV:

Line tower, quad circuit
Angle tower 1, quad circuit
Angle tower 2, quad circuit
Transposition tower, quad circuit

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 PL1a S2
SEE PL1a S30
SEE PL1a S60
SEE PL1a ST45
SEE PL1a ST90
SEE PL1a D2
SEE PL1a D30
SEE PL1a D60
SEE PL1a D90
SEE PL1a DT/DT45
SEE PL1a DT90
SEE PL1a DX

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).

SEE PL1(b) S2
SEE PL1(b) D2
SEE PL1(b) D30
SEE PL1(b) D60
SEE PL1(b) DX

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:

Line, 132/33 kV single earthwire
Line, 132/33 kV double earthwire
Line, 132/33 kV with spire
Transposition, 132/33 kV
Angle 1, 132/33 kV, single earthwire
Angle 1, 132/33 kV, double earthwire
Angle 2, 132/33 kV, peak 1
Angle 2, 132/33 kV, peak 2

Uprated 132 kV double circuit towers:

Line, 132/132 kV
Line, 132/132 kV with spire
Transposition, 132/132 kV with spire
Angle 1, 132/132 kV, peak 1
Angle 1, 132/132 kV, peak 2
Angle 2, 132/132 kV, peak 1
Angle 2, 132/132 kV, peak 2
Angle 2, 132/132 kV with spire

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.

CE PL3 S2
CE PL3 D30
CE PL3 DD30

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”.

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

Lydney

Lydney” is a temporary designation for towers found around Lydney, Gloucestershire. There is no visual material from which diagrams can be produced. 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.

SEE PL7 D2
SEE PL7 DD2
SEE PL7 D10
SEE PL7 DD10
SEE PL7 D30
SEE PL7 DD30
SEE PL7 D60
SEE PL7 DD60
SEE PL7 DT
SEE PL7 DT (ETC)
SEE PL7 DDT
SEE PL7 DDT (ETC)
SEE PL7 DDT90

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.

K5735 DD2

STL1

See under PL16 below.

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)”).

“Scottish” (K1201) S2
“Scottish” (K1201) S60
“Scottish” (K1201) ST
“Scottish” (K1201) SST
T1073 S30 (rotated base)
T1073 S60 (rotated base)
SWE PL16 D2
STL1 K9857 D2 (PL16 D2S)
SWE PL16 DD2
STL1 K9857 DD2 (PL16 DD2S)
SWE PL16 D10
SWE PL16 DD10
SWE PL16 D30
SWE PL16 DD30
SWE PL16 D60
SWE PL16 DD60
SWE PL16 D90
SWE PL16 DD90
D60 Junction (unconfirmed)
K1124B D90 Junction
SWE PL16 DT
SWE PL16 DT90
SWE PL16 DDT
SWE PL16 DDT90
K1124B DT through-line

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.

Blaw Knox K1420 S10
Blaw Knox K1420 S30
Blaw Knox K1420 S60
Blaw Knox K1420 ST

Associated intermediates:

Steel lattice tower (route XCW)
Suspension pole (SWE region)
Suspension pole (NOSHEB region variant 2)

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 (L16) D2
J L Eve (L16) D10
J L Eve (L16) D30
J L Eve (L16) D60
J L Eve (L16) D90
J L Eve (L16) DT/DT90
J L Eve (L16) DT variant 2
J L Eve (L16) DT variant 2/+1
J L Eve (L16) DT variant 2/+2
J L Eve (L16) DT variant 3
J L Eve (L16) DT variant 4
J L Eve (L16) DT variant 5/+1
J L Eve (L16) DT90
J L Eve (L16) universal crossunder gantry

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.

Eve 0.175 D2
Eve 0.175 D2 (uplift)
Eve 0.175 DD2
Eve 0.175 D10
Eve 0.175 D30
Eve 0.175 D60
Eve 0.175 DT
Eve 0.175 DT variant 2
Eve 0.175 DT90

J L Eve C772

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

Eve C772 D2
Eve C772 D10
Eve C772 D30

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.

Eve C1415 D2
Eve C1415 D10

Quoich–Broadford

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

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.

L4(m) D STD
L4(m) D30 STD
L4(m) D60 STD
L4(m) D90 STD
L4(m) DT STD
L4(m) DJT STD
L4(m) ST STD
L4(m) SF60 STD
L4(m) SF60 M6

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:

L4(m) S (A)
L4(m) S (B)
L4(m) S30 (A)
L4(m) S30 (B)
L4(m) S60 (A)

L7

L7 appears to be another 132 kV type. Unlike other 132 kV types, L7 supports twin conductor bundles.

L7 or L7(c) D (BICC)
L7(c) D30 (J L Eve)
L7(c) D60 (J L Eve)
L7(c) D90 (BICC)
L7(c) DT (J L Eve)
L7(c) DT (basic crossarms)
L7(c) DJT (BICC)
L7(c) ST (J L Eve)
L7(c) SF60 0–30°
L7(c) SF60 30–60°

275 and 400 kV

L34

L34 is a flat single-circuit 275 kV type.

L34 S1
L34 S10
L34 S30
L34 S60

PB

PB” is a single circuit, flat formation 132 kV tower series alleged to be from Painter Brothers. Painter Brothers was a steelwork fabricator not presently known to have designed towers, but it is not impossible for them to have done so. “PB” is probably not a real designation either.

L66

L66 is a rare type similar to L3 and L3.

L66 D2 STD
L66 D30 STD
L66 D60 STD

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.

L2 D
L2 D DMC
T1648 D
L2 D10
L2 D15 EWCO
L2 D30
L2 D30 DMC
L2 D40 EWCO
L2 D60
L2 D60 DMC
L2 D90
L2 DJ
L2 DJX
L2 DT
L2 DTU (0–5° entry)
L2 DT45
L2 ST
L2 STX
L2 380ST
L2 SFX MH
L2 SFX E16

L3

Blaw Knox L3 is a scaled-down version of L2 that is 275 kV only. As with L2, it is twin conductor. There is also an Eve version of L3.

Blaw Knox L3

Blaw Knox L3 D
Blaw Knox L3/L3(c) DS
Blaw Knox L3/L3(c) D10
Blaw Knox L3/L3(c) D30
Blaw Knox L3/L3(c) D40 EWCO
Blaw Knox L3/L3(c) D60
Blaw Knox L3 DJ
Blaw Knox L3 DJX
Blaw Knox L3 DT
Blaw Knox L3 DT45?
Blaw Knox L3 DTV45/DTU45 (0-5° entry)
Blaw Knox L3 ST

J L Eve L3

J L Eve L3 D (C673)
J L Eve L3 D (C864)
J L Eve L3 D10
J L Eve L3 D30
J L Eve L3 D60
J L Eve L3 DT

Blaw Knox T2175

Blaw Knox T2175 is a derivative of L3.

T2175 D STD
T2175 D10 STD
T2175 D30 STD
T2175 D60 STD

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.

BES L6 D (1960)
BEBS L6 D (1966)

Balfour Beatty L6

L6 BB D STD
L6 BB D20EC STD
L6 BB D30 STD
L6 BB D40EC STD
L6 BB D60 STD
L6 BB D90 STD
L6 BB DJT STD
L6 BB DT STD
L6 BB ST STD
L6 BB SF60 5–30° STD

BICC L6

SF60 omitted due to chart errors.

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

L6 BICC D STD
L6 BICC D20EC STD
L6 BICC D30 STD
L6 BICC D40EC STD
L6 BICC D60 STD
L6 BICC D90 STD
L6 BICC DT STD
L6 BICC DJT STD
L6 BICC ST STD

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

Dungeness “headless” L6 BICC D30 M20′

Blaw-Knox L6

L6 BK D STD
L6 BK D30 STD
L6 BK D60 STD
L6 BK D90 STD
L6 BK DT STD
L6 BK DJT STD
L6 BK ST STD
L6 BK SF60 STD

J L Eve L6

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

L6 JLE D STD
L6 JLE D20EC
L6 JLE D30
L6 JLE D40EC STD
L6 JLE D60 STD
L6 JLE D90 STD
L6 JLE DJT STD
L6 JLE SF60

L6(c)

L6(c) D STD (BICC)
L6(c) D30 STD (J L Eve)
L6(c) D60 STD (BICC)
L6(c) D90 STD (J L Eve)
L6(c) DJT STD (J L Eve)
L6(c) DT STD (BICC)
L6(c) SF60 STD 0–15° (BICC)
L6(c) SF60 STD 15–45° (BICC)
L6(c) SF60 STD 45–60° (BICC)

L6m

L6m D STD
L6m D30 STD
L6m D60 STD
L6m DJT STD
L6m ST STD

L8

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

L8(c) D STD 400 kV
L8(c) D30 STD 400 kV
L8(c) D60 STD 400 kV
L8(c) D90 STD
L8(c) DT STD 400 kV
L8(c) DJT STD
L8(c) ST M7.3 (M24′)
L8(c) SF60 STD 0–20°
L8(c) SF60 STD 20–60°

Smaller 275 kV towers:

L8 RD STD
L8 RD M4.9 (M16′)
L8 RD M7.3 (M24′)

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:

L8 S STD

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.

L9 D2

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 D 400 kV
L12 D10 400 kV
L12 D25 400 kV
L12 D55 400 kV
L12 D90 400 kV
L12 DT Mk 1
L12 DT 400 kV

L12 low height:

L12 LD

L13

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

L13 D
L13 D60
L13 LD

SSE400

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

SSE400 D/DL
SSE400 D (lower strength)
SSE400 D10
SSE400 D25
SSE400 D55
SSE400 D90
SSE400 DT