Belfast four-circuit towers

Contents

• Overview
  • General data
  • Progress
• Lines
• Tower forms
  • Examples
• Examples
• See also

Overview

This is a type of UK electricity pylon (steel lattice transmission tower) used for a dual-voltage line in Belfast. According to NIE Networks, the towers were designed by Callender’s and originally carried dual-voltage 110 kV plus dual-voltage 33 kV; the line is said to date to 1932. The crossarms for the 33 kV circuits have since been removed. In contrast to the Rannoch–Abernethy type, the upper 33 kV crossarm carried two phases per side, with the lower 33 kV crossarm carrying one phase per side.

All the towers have ladders instead of step bolts.

Although the line was energised at 110 and 33 kV, the towers could conceivably be rated for 132/33 kV. Such has been claimed—specifically, that all 110 kV lines in Northern Ireland have 132 kV clearances—but this remains unproven. With standard UK designs, the truth of this claim is evident from the relative size of the insulators compared to the crossarm spacing, but it’s less clear with these towers.

General data

Design contractor	Callender’s
Found
Height (straight line tower)	Unknown
Voltage	2 × 110 kV + 2 × 33 kV (design)
Conductors	Single
Circuit count	Dual voltage double+double
Design conductor	Unknown
Design earthwire	Unknown
Normal span	Unknown

Progress

Lines

The towers are used for a single line in East Belfast that presently runs from Airport Road substation (where it terminates on a PL16 DT) to Rosebank substation. The line has been de-rated and is likely now operating at 33 kV. This includes replacement arcing horns to reduce the arc gap length. The original line ran a little further at the north end, but the last few towers have been demolished and the PL16 DT erected outside Airport Road substation.

Tower forms

Northern Ireland Electricity Networks don’t own the drawings of their own towers: these are the property of National Grid, despite Northern Ireland having never been part of the CEB, CEGB or National Grid. As such, no material is expected to be available and they refuse to provide any clues, such as tower heights. The difficulty in understanding the scale (since the voltage clearances—110 or 132 kV—are not verified) prevents attempting preliminary drawings.

The line tower peak is very similar to the peak of the Callender’s-designed SWE PL1 S2 single-circuit line tower. The line towers are similar to those of SEE PL1(b) (also Callender’s) but this is where the similarity ends.

Examples

The designations and deviation limits of each of the tower types is yet to be determined; the angle tower types are simply numbered here by ascending deviation limit. Angle 3 seems to have a 90° limit however.

Examples

See also

Four-circuit configuration. No response from the copyright holder, so these images are just dumped into a list for your inconvenience …

• Line tower, Beersbridge Road, July 1981
• Line tower, East Bread Street, October 1982
• Line tower, Grand Parade, July 1980
• Line tower obscured by watermark, June 1986
• Line tower, Newtownards Road, March 1982
• 33 kV crossarm detail, June 1984
• Smallest angle, Dee Street Bridge, March 1984
• Smallest angle, Sydenham By-Pass, May 1991
• Largest angle, Mersey Street, June 1981
• Largest angle, Victoria Park Station, September 1981
• Ladder detail, March 1984
• Possible 33 kV termination point, Connswater, August 1987
• Retermination on PL16 DT, Sydenham By-Pass, March 1984