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?

B2003

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

On Mon, 12 Apr 2010 14:50:26 +0100
"Paul Scott" wrote:
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.

Raising the voltage does seem an odd thing to do not least because they dropped
the voltage from 640V years ago citing power saving reasons (which sounds like
rubbish TBH , lower voltages are less efficient , not more).

B2003

"Paul Scott" wrote in message
...
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

The Central Line is already 750V - it was converted with the last upgrade.

There is still a difference between nominal voltages on LUL (4 rail) & NR (3
rail).

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK

On 12/04/2010 14:56, d wrote:

Raising the voltage does seem an odd thing to do not least because they dropped
the voltage from 640V years ago citing power saving reasons (which sounds like
rubbish TBH , lower voltages are less efficient , not more).

.... unless the lower voltages leak less.

On Mon, 12 Apr 2010 14:57:36 +0100
"Peter Corser" wrote:
The Central Line is already 750V - it was converted with the last upgrade.

Does that mean the western central line can't be used for stock moves any
more except for 92 stock?

B2003

Basil Jet wrote:
On 12/04/2010 14:56, d wrote:

Raising the voltage does seem an odd thing to do not least because
they dropped
the voltage from 640V years ago citing power saving reasons (which
sounds like
rubbish TBH , lower voltages are less efficient , not more).

... unless the lower voltages leak less.

Lower voltage means a higher current draw for the same power, and
transmission losses are proportional to I^2.

Rgds

Denis McMahon

On 12 Apr, 15:28, wrote:
On Mon, 12 Apr 2010 14:57:36 +0100

"Peter Corser" wrote:
The Central Line is already 750V - it was converted with the last upgrade.

Does that mean the western central line can't be used for stock moves any
more except for 92 stock?

B2003

Doesn't Bakerloo tube stock run on 750 V beyond Queens Park?

On Apr 12, 2:33*pm, 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?

B2003

The issue on LUL is that at a nominal voltage of 750 V, the maximum
voltage that could be seen at the train could be 900 V (under light
loading conditions) and equipment in some of the older stock could be
vulnerable to damage at such a voltage (eg by flashover). This
particularly applies to starting resistances. It is for this reason
that the Southern's line voltage is kept to 660 V in the inner
suburban area (to about 15 miles from London, plus branches like
Tattenham Corner and Epsom Downs), owing to the interfaces at Waterloo
(W&C), East Putney, Wimbledon, Gunnersbury and Richmond, and the
complexity of the inner suburban network.

(Although not used by Southern trains, the Richmond - Gunnersbury
section is part of the SR electrification system and is separated from
the NLL system at Gunnersbury Junction by a gap in the con-rail. A
similar gap also exists on the District Line.)

The line voltage is graded upwards outside the suburban area; on the
Brighton Line, for example, the last 660 V substation is Coulsdon
North (IIRC).

The NLL and Euston - Watford DC electrification remains at 650 V owing
to the inteface with the Bakerloo Line at Queen's Park. Beyond there,
instead of the standard LU +400 and -230 V arrangement, the outside
conductor rail is at 650 V and the centre one is bonded to the running
rails; these cross-bonds can be seen at regular intervals. Beyond
Harrow and Wealdstone, the redundant centre rail is retained to reduce
the resistance of the traction return circuit, as the DC lines only
use single-rail track circuits, unlike the Southern which uses double
rail.

I understand that LUL has a long-term strategy to upgrade the line
voltage to 750 V, and all new stock is capable of this, but until the
last of the older stock is withdrawn (I believe that the D stock
cannot operate at 750 V but subsequent builds can), this will not be
possible across the complete network.

HTH.

On Mon, 12 Apr 2010 08:20:25 -0700 (PDT), MIG
wrote:

On 12 Apr, 15:28, wrote:
On Mon, 12 Apr 2010 14:57:36 +0100

"Peter Corser" wrote:
The Central Line is already 750V - it was converted with the last upgrade.

Does that mean the western central line can't be used for stock moves any
more except for 92 stock?

B2003

Doesn't Bakerloo tube stock run on 750 V beyond Queens Park?

According to :-
http://www.statemaster.com/encyclope...-Great-Britain

the DC line is 650v which ISTR has been stencilled on many trackside
cabinets for years. OTOH the native trains have been able to run on
750v since at least the c.501 if not also the immediately preceding
LMS trains. ATM there doesn't seem to be an "official" confirmation
which leaps to the front of the Google queue.