NG TS 3.04.03 PDF

This document specifies the design and application of lattice steel tower overhead line constructions of the L12 family to be used at 400 kV with twin 700 mm2 or 850 mm2 (all aluminium alloy phase conductors, AAAC).

The L12 constructions for which detailed lattice steel tower designs are currently available are:

L12: The original design of lattice steel towers with design loadings and application criteria which met the requirements of the Electricity (Overhead Lines Regulations) 1970. This construction uses twin 700 mm2 AAAC phase conductors with a single 425 mm2 AAAC earthwire.

L12A: The L12 design of lattice steel towers with design loadings and application in accordance with NGTS 2.4 for twin 700 mm2 phase conductors and a 160 mm2 aluminium alloy conductor steel reinforced (AACSR) or a fibre optic equivalent earthwire as defined in NGTS 3.8.9.

L12A/1: The L12 design of lattice steel towers with design loadings and application in accordance with NGTS 2.4 for twin 850 mm2 AAAC phase conductors and 160 mm2 AACSR or a fibre optic equivalent earthwire.

L12 L: This is a new low height lattice steel construction with design loadings and application in accordance with NGTS 2.4 for the same conductor systems as L12A.

A rotated conductor bundle may be used on L12, L12A and L12A/1 where conductor galloping is a problem. A suffix R shall be appended to the line designation.

The design details of the original L12 steel lattice towers are included in this Specification to allow the procurement of new conductor systems, insulators or fittings for existing lines. The design loadings should be calculated using the L12A parameters.

If any of the above constructions are considered for other conductor arrangements, advice on the application should be obtained from The National Grid Company.