On Tue, 29 Jul 2014 18:42:53 +0100, The Natural Philosopher
wrote:

Mind you the AL ones are wound on steel cores.

Aluminium wound over steel is an older conductor design method commonly used for
supergrid installations until the late 1980's in the UK but these are often a
bottleneck on the network, so as they eventually succumb to corrosion and
internal failure they are not always being replaced like for like. During many
refurbs and upgrades they now use either an all aluminium design or aluminium
over a loose steel core (termed a gap conductor), with grease filling the gap
between the two.

There are developments in the pipeline for aluminium conductors over a composite
core, possible first large scale use in the UK would be on the route of the
upgraded 132kV to 400kV route for Hinkley Point C

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