L9
Contents
Overview
L9 is a UK electricity pylon (steel lattice transmission tower) series designed by J L Eve to a 1966 specification (BES-L9-1966, Ministry of Power designation CEGB/400/L9/1966) for low-height lines. L9 is the low-height equivalent to L6 (quad 0.4□″ SCA conductors carrying 400 kV). L9 is similar to the later L12 low-height; the L12 low-height suspension tower (L12 LD) uses standard vertical suspension insulator strings instead of the V-formation pairs used by L9 series. (L9 still needed two insulator strings per phase, just as did L6, but L6 placed both strings side-by-side.)
L9 towers are two-tier in construction, with four phases on the bottom tier and two on the top tier, reducing the height but increasing the width. This arrangement is known as “Donau” (Danube) in Germany and is a popular configuration there, but in Britain three-tier towers are preferred, possibly to reduce wayleave width. L9 and the later L12 low-height towers are rare; when used, it is where the total height of the power line or the towers themselves must be minimised, such as around runways.
L9 towers were designed to be fitted with ladders, for unclear purposes; the ladder is not always present and may not reach as far down as originally designed.
“L9” on this site covers both L9 and L9(c) given that they are visually indistinguishable.
General data
| Designer | J L Eve |
|---|---|
| Found |
|
| Known subtypes | L9, L9(c) |
| Height (straight line tower) | 31.7 m |
| Voltage | 400 kV |
| Dates back to |
1966 (specification) 1976 (L9(c)) |
| Conductors | Quad |
| Circuit count | Double |
| Design conductor | Quad 0.4□″ SCA (now 400 mm² Zebra ACSR) |
| Design earthwire | 0.4□″ SCA (now 400 mm² Zebra ACSR) |
| Normal span | ? |
Tower forms
The following diagram is shown to scale at 12 pixels per metre:
The L9 and L9(c) LD30, LD20 EC, LD60 and LD40 EC tension towers are all identical in outline. All four share the same general arrangement and erection diagram for the crossarms, while the tower body for LD60/LD40 EC has separate drawings from that of LD30/LD20 EC due to differences in the bar and plate dimensions and shapes.
The standard span is not known. The lowest (inner bottom) conductor bundle centre (of all L9 towers) is 16.5 m from the ground, compared to around 20 m for L6 D30, suggesting possibly a shorter span would be needed.
Tower details
See dimensions on the site guide page for a key to the tables.
| Type | Source | Height | Base width | Crossarm width |
|---|---|---|---|---|
| L9 LD | 35/5163 | 104′–0″ (31.7 m) | 22′–0″ (6.7 m) | 111′–0″ (33.9 m) |
| L9(c) LD30 | L9C/58 | 32.0 m | 10.2 m | 28.3 m |
| L9(c) LD20 EC | ||||
| L9(c) LD60 | L9C/101 | |||
| L9(c) LD40 EC |
See also
- L6 and L9, Gloucester (Flickr album)
- L9 LD (Flickr)
- L9 angle tower (Flickr)
- L9 angle tower, alternative angle (Flickr)