d wrote:
I read about this in wikipedia but is it actually going to happen? If
so what will happen on sections where tube and sub surface stock run
on the same track - ie raynors lane to uxbridge and acton town to
ealing common. Will these sections be kept at 630V or will the
piccadilly stock be able to handle 750V anyway?

There is definitely a power supply upgrade going on, just announced he

http://www.tfl.gov.uk/corporate/medi...tre/15249.aspx

but they don't explicitly say they are raising the system voltages - it
wouldn't necessarily follow anyway, the regulated voltage could stay the
same but with a higher current draw being allowed.

Related to this, there are apparently Network Rail projects going on at the
moment to separate out all the mainline and 'tube' supplies where they are
connected, to allow the NR third rail voltage to be raised to a standard 750
volts, and to allow regenerative braking. An example is the Waterloo and
City, still fed off the SR for obvious historic reasons.

What I'm wondering is that if LU adopted a 750 volt standard on the SSR, NR
wouldn't necessarily need to do this - unless they want to have separate
billing anyway - there's also practicalities such as isolations for
maintenance.

Paul S