Crossing towers

Contents

• Overview
• Standard types
  • PL1 crossings
  • PL16 crossings
• Custom types

Overview

Special tall towers are required when crossing wide rivers. Their height makes many examples impractical to show at this site’s scale of 12 pixels per metre, as they would not fit on the monitor. They are collected together on this page for that reason and because many are one-off types that do not warrant a dedicated page each.

Standard types

There are at least two designs of crossing tower used widely across the UK. Named “PL1” and “PL16” here, both appear to be contemporary 1930s original grid types, although the “PL16” type is so-named as it is prevalent on PL16 lines. While considerably slimmer than the “PL1” type, this apparently does not reflect any difference in age, and there may be some other technical reason for the differences in profiles.

PL1 crossings

Multiple PL1 lines share the same type of crossing tower, shown below at estimated sizes to scale at 12 pixels per metre:

The basic design accepts double circuit crossarms with a maintenance platform below. Most of the examples discovered instead are single circuit, with the spare side of the top crossarm used to carry the earthwire.

In Dumfries it has been built to around 160 feet tall for the River Nith crossing, just south of Kingholm Quay. The towers are around 730 feet (223 m) apart, a comparatively short span. Two more towers are used for a long span crossing in Plymouth; this span is around 2,226 feet (678 m), over twice the standard span of a 132 kV tower. This span uses triple vibration dampers at each end due to its exceptional length. These towers are closer to 96 feet tall (around 29 m), maybe only 10–15 feet taller than typical standard height for 132 kV.

The towers at Dumfries and Plymouth are used on PL1 single-circuit lines (SS PL1 and SWE PL1 respectively). The same type can be found in Exeter with the missing third crossarm.

The tower adjacent to the Gloucester and Sharpness canal is on an SWE PL1 single-circuit line. The lowest height extension is subtly different (in terms of bracing) to that used at Exeter.

Another double-circuit example (with work platform) can be found in Skewen, Wales, alongside the Tennant Canal and River Neath. This is also on an SWE PL1 line.

There is a crossing over the River Severn on the SWE PL1 line that leads to Lydney; the two towers appear to be this type, single circuit form with working platforms.

PL16 crossings

Multiple PL16 lines share the same type of crossing tower. This type is considerably slimmer than the “PL1” type. All indications are that these towers are PL1-era; the reason for the narrower profile compared to the “PL1” type is not known. Two such towers existed in Avonmouth prior to their removal; according to National Grid, they had been there since the 1930s, which appears to be borne out by historic aerial photography.

Based on the examples below, it appears that this type remained current into the PL16 era.

Size estimated and shown at a scale of 12 pixels per metre.

Examples, all D2S-type PL16 lines unless otherwise stated:

• Two towers spanning the River Welland east of Fosdyke and Fosdyke Bridge, Lincolnshire; route HW
• Two more towers on the same line, spanning the River Nene south of Sutton Bridge
• Two towers spanning the River Great Ouse north of King’s Lynn, Norfolk
• Four towers (parallel routes PD and PKB) crossing the Swale between mainland Kent and the Isle of Sheppey, near Kingsferry Bridge
• Two towers spanning the River Medina, north of Newport, Isle of Wight
• Two can be seen side-by-side south of Arlingham on (at this location) the north bank of the River Severn; one line is SWE PL1 and the other is 33 kV. These are extra-tall towers with the working platforms fitted. The tower type(s) on the far bank remain unidentified.
• The crossing over the River Usk in Newport (South Wales) uses two extra-tall towers, both fitted with working platforms; the east tower is a D60 carrying a deviation of around 40°. This short line uses a mixture of towers, including PL16, SWE PL1 and L4(m).
• One of the four lines crossing the River Ribble west of Preston, Lancashire.

Custom types

The Clyde, Cart and Forth crossing diagrams are from [Grid 1929]. The Roding crossing diagram is from [Marshall] (1933). None of the crossings depicted still exist, and it’s unlikely that the original drawings will be unearthed now.

The diagrams are to half scale at 6 pixels per metre.

The River Clyde crossing was unusual in that Yoker substation was on the inside of the crossing span. On the far bank, there were two (presumably single circuit) anchor towers, with the line dividing at the crossing tower. The anchor tower therefore had a special crossarm configuration.

The River Roding crossing carried four 66 kV circuits.