electrickery

We watched them pulling a new cable through the high tension power line today. It's a 115kV line. They are replacing the insulators and using a new Aluminium with steel core cable to replace the old only Aluminium cable. The new cable is half the area (2/3 the diameter) and yet carries 400A more (he wasn't sure that actually capacity of the line, though we can assume that it was at least 1kA to begin with, giving a total line capacity of 115MW). Normally they perform the entire operation with helicopters, but due to the difficulty of the location and the proximity to residential areas the whole thing was done with people on cherry pickers and climbing the tower. I got a souvenir:

I think I'll use it as speaker cable. The reason that it is smaller and yet higher capacity is due to the fact that by using a separate tensile support they can use a very high purity Al (it is soft enough to cut with a kitchen knife). For reasons I'm not entirely clear about, impurities dramatically reduce the conductivity of metals (for example, a 10% silver 90% copper alloy is only half the conductivity of copper or silver).

Also randomly today I got a solar panel:

It is from my friend John in NZ who is doing research into solar something. The intent is for me to set it up on a roof somewhere and plug in his control system. I shall await the next installment.

comments

Peter Eckersley: "for reasons I'm not entirely clear on", just imagine an appropriately modified solution to the Schrödinger equation. :)




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