Tom Anderson wrote:
wouldn't it have made sense to build the underground to be
compatible with the rest of the network, as, AIUI, in Tokyo?

Digressing a bit, I've always wondered why the South coast of England
(mainly the South East) uses the 700V DC "third rail" system for electrical
power, when the entire rest of the UK uses the 25000V AC overhead cable
system. Wouldn't it make more sense to have the same used all over the UK?
It means that a lot of national-running trains have to be diesel.

--
"We are now approaching Paisley Gilmour Street"

AyrAlex wrote:
Tom Anderson wrote:

wouldn't it have made sense to build the underground to be
compatible with the rest of the network, as, AIUI, in Tokyo?


Digressing a bit, I've always wondered why the South coast of England
(mainly the South East) uses the 700V DC "third rail" system for electrical
power, when the entire rest of the UK uses the 25000V AC overhead cable
system. Wouldn't it make more sense to have the same used all over the UK?
It means that a lot of national-running trains have to be diesel.

I know little of the history of the Southern Railway, but I believe that
it was decided to let the electrification, parts of which were done back
in the time of Yerkes, to proceed apace - IIRC this electrification
contributed to the sparse tube coverage in South London.

Besides, wasn't 25kVAC thought up well after 700V DC anyway?

Brad

"Alex":
Digressing a bit, I've always wondered why the South coast of England
(mainly the South East) uses the 700V DC "third rail" system for
electrical power, when the entire rest of the UK uses the 25000V AC
overhead cable system. Wouldn't it make more sense to have the same
used all over the UK?

In principle yes, but the Southern network is already pressing the limit
of what is economical as regards both distance and speed for third-rail
trains. Most systems that use it don't have journeys anywhere near as
long as London to Bournemouth or Dover. Low-voltage power requires
frequent substations due to voltage drop, and the amount of current that
can be conveyed is also limited. And if it's DC, it additionally requires
AC-to-DC conversion at every substation.

Besides, wasn't 25kVAC thought up well after 700V DC anyway?

Which completes the story.
--
Mark Brader, Toronto | "When you're up to your ass in alligators, maybe
| you're in the wrong swamp." -- Bill Stewart

My text in this article is in the public domain.

On Wed, 26 May 2004 16:43:32 +0000 (UTC), TheOneKEA
wrote:


I know little of the history of the Southern Railway, but I believe that
it was decided to let the electrification, parts of which were done back
in the time of Yerkes, to proceed apace - IIRC this electrification
contributed to the sparse tube coverage in South London.

Besides, wasn't 25kVAC thought up well after 700V DC anyway?


This last point is the key to it. The technology to make 25kV
possible, in particular the ability to convert the AC supply to a much
lower voltage DC on board a train, only really became available from
around 1945 onwards. A lot of the former Southern Railway was
electrified much earlier than this. Converting it from 3rd rail to
the overhead system would have been very expensive - almost as
expensive as electrifying it from scratch.

Martin

AyrAlex (AyrAlex) wrote in message news:f%0tc.51$YT4.7@newsfe5-win...
Tom Anderson wrote:
wouldn't it have made sense to build the underground to be
compatible with the rest of the network, as, AIUI, in Tokyo?

Digressing a bit, I've always wondered why the South coast of England
(mainly the South East) uses the 700V DC "third rail" system for electrical
power, when the entire rest of the UK uses the 25000V AC overhead cable
system. Wouldn't it make more sense to have the same used all over the UK?
It means that a lot of national-running trains have to be diesel.

No , they could be dual voltage like the Thameslink trains or WAGN services
to Moorgate. Also 750V 3rd rail is used up in Merseyside too. Bear in mind
however that outside of the southeast , merseyside and strathclyde regions,
only a small percentage of the local lines are electrified by any means and
even the midland mainline to nottingham and derby is still diesel powered
past Bedford.

B2003

On Wed, 26 May 2004 13:31:53 +0100, AyrAlex
(AyrAlex) wrote:

It means that a lot of national-running trains have to be diesel.

Or be multi-voltage, as most modern electric trains (at least
potentially) are - Electrostar, Desiros, 319s, 365s, EMUs Silverlink
and WAGN use in London, Eurostars.

I can't think of any services which are diesel because of the two
electrification systems. They are diesel simply because of a lack of
electrification.
--
Arthur Figgis Surrey, UK

It means that a lot of national-running trains have to be diesel.

Or be multi-voltage, as most modern electric trains (at least
potentially) are - Electrostar, Desiros, 319s, 365s, EMUs Silverlink
and WAGN use in London, Eurostars.

I can't think of any services which are diesel because of the two
electrification systems. They are diesel simply because of a lack of
electrification.

I can think of some which used to run: the North-West to Brighton
services via the Trent Valley and the WLL.

James wrote:
It means that a lot of national-running trains have to be diesel.

Or be multi-voltage, as most modern electric trains (at least
potentially) are - Electrostar, Desiros, 319s, 365s, EMUs Silverlink
and WAGN use in London, Eurostars.

I can't think of any services which are diesel because of the two
electrification systems. They are diesel simply because of a lack of
electrification.

I can think of some which used to run: the North-West to Brighton
services via the Trent Valley and the WLL.

Which electrification system is used on the WLL?

Piccadilly Pilot wrote:
James wrote:
It means that a lot of national-running trains have to be diesel.

Or be multi-voltage, as most modern electric trains (at least
potentially) are - Electrostar, Desiros, 319s, 365s, EMUs
Silverlink and WAGN use in London, Eurostars.

I can't think of any services which are diesel because of the two
electrification systems. They are diesel simply because of a lack
of electrification.

I can think of some which used to run: the North-West to Brighton
services via the Trent Valley and the WLL.

Which electrification system is used on the WLL?

750V DC 3rd rail from Clapham Junction to (IIRC) Mitre Bridge Junction,
where it becomes 25KV AC overhead.
--
Richard J.
(to e-mail me, swap uk and yon in address)