On Fri, 17 Mar 2006, Clive D. W. Feather wrote:

In article , Tom Anderson
writes

What might be sensible would be if preparatory work for the change was
done now - for instance, stringing catenary to Shepherd's Bush, but not
wiring it up to the mains.

Do you think it would still be there in 6 years time?

I have to admit that it had never occurred to me that people might steal
it. Okay, scratch that - but could there be other bits of work that could
be done cheaply now?

With any luck, the changeover could then be done just by setting some
jumpers in a cable cabinet somewhere, rather than having to get the
permanent way gang out again.

I would hope it would be deliberately made a lot harder than that. Do
you really want an accident waiting to happen?

You mean like maybe sticking some masking tape over it? Seems a bit
paranoid, but if you insist.

And I do not understand what the hell resignalling of the Hammersmith
and City Line has to do with this at all!

This, i have to admit, is a puzzle - how the hell is the H&C wired to
the WLL?

It isn't, but there are such things as earth leakage and induction.

Righto. I hadn't realised these things were powerful enough that you could
get coupling between two lines which simply cross one another on different
levels at one point.

I know someone involved in the electrification work on CTRL2. He has to
worry about the fact that the Underground tube tunnels, the King's Cross
station structure, the St.Pancras station structure, and the NLL all
have different values for "earth". He reckons that if he gets things
wrong, opening a breaker at Ashford could cause a lethal change in earth
voltage at the KXSP complex.

Eek.

tom

--
Why do we do it? - Exactly!