SEE SL3

Contents

• Overview
  • General data
• Lines
• Tower forms
  • Single circuit
  • Double circuit
  • Examples
• Tower details

Overview

SEE SL3 is 33 kV distribution tower series designed by Watshams in 1930. SEE SL3 D60/DT appears to be identical to SEE SL2 D60/DT, although no other drawings from SEE SL2 have been recovered. This page also incorporates the variant depicted in [Marshall] as the standard 33 kV type in 1933, which seems to be virtually identical to SEE SL3, as well as the variant type used on the line between Luton and Aylesbury.

Unfortunately, Watshams appear not to have meaningful drawing number ranges or identifiable contract numbers and with SEE SL3 being the only (albeit partial) set of drawings recovered, this is the identity being used at present. The identity listed here may be changed at a later date should more detailed information come to light.

The bend line for the D3, D20, S3 and S20 towers is at ground level, making these narrow base towers; these types use earth foundations. The 60° and terminal towers are more characteristic wide base towers with concrete pyramid foundations.

Also covered on this page are some related types, derivatives and precursors of SEE SL3 where almost identical in design.

Per [Marshall], the design conductor is given to be 0.1^□″ SCA. (SEE SL3 is not named, but the illustrations match SEE SL3.)

General data

Lines

Known lines include:

• Luton–Aylesbury (almost identical type to SEE SL3)
• Reading–Basingstoke–Hook ring (suggested to be SEE SL3)

Tower forms

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

Single circuit

There are also variants of these towers with earthwire peaks, for example this (likely height-extended) tower at New Mills in Derbyshire (originally a line from Buxton to New Mills):

Double circuit

The line from Luton to Aylesbury appears to use a D3 tower that has a slightly larger peak and slightly broader top crossarm than that of SEE SL3. Details on this type are not known.

SEE SL2 general arrangement drawing 1156 covers type D60 and DT; details for the DT top hamper are covered by drawing 1159, not recovered. D60 parts have an “H” suffix to the erection marks, while DT parts have a “J” suffix; the erection diagram should indicate the differences between the two. [Marshall] shows the DT as being the type with integrated cable sealing ends, while the recovered drawings imply downleads. The general arrangement drawing for SEE SL3 D60 bears a handwritten inscription “SL3 D60+DT” but does not offically mention “DT”.

Examples

Pending.

Tower details

Crossarm width is the total width across the longest crossarm on each side.

Phase clearances do not take into account the length of the suspension insulator strings or earthwire suspension shackle length (hence crossarm-to-crossarm only) and are for comparison within class only.