On Saturday, 18 March 2017 00:07:59 UTC, James Wilkinson Sword wrote:
Despite extensive googling, there seems to be nothing that tells me how much
current flows along wires on a national grid pylon. They only list voltages.
Anybody know?

A 400 kV National Grid circuit may carry 1 kA in each of its three phases, thus transmitting a power of 700 MW.
A 132 kV distribution circuit may carry 300 A in each of its three phases, thus transmitting a power of 70 MW.
An 11 kV distribution circuit may carry 150 A in each of its three phases, thus transmitting a power of 3 MW.
A 400 V final distribution circuit may carry 200 A in each of its three phases, thus transmitting a power of 150 kW.

(Remember, these voltages are phase-to-phase voltages, the phase-to-earth voltages are 1.73 times lower. Thus (400 kV/1.73) x 1kA x 3 = 700 MW.)

http://www.emfs.info/what/terminology/ (site maintained by National Grid)

[Pylon type] L12 is effectively the L6 replacement will take twin conductors up to 850mm2, but all aluminium conductor rather than the heavier steel cored kind formerly used.

http://www.gorge.org/pylons/structure.shtml

Owain