On 7 Dec 2006 14:14:32 -0800, Boltar wrote:

LUL trains can still run over 750V lines as they currently do on the
District and Bakerloo lines.

Yes , but arn't those lines set up so that 3rd rail stock gets 750V but
4 rail LU stock still only gets 630V?

No. The 3rd rail is +750V* and the 4th rail is 0V (and is bonded to
the running rails). If the 4th rail were at +120V, it would give the
arrangement you describe.

*Although someone has written on Wikipedia that it's actually 690V - a
"compromise" between the usual voltages for NR and LU stock.