I'm visiting London in a few weeks and being an 'electric train' kind of
nut I'm interested in seeing the voltage change over points.

 The Thameslink change over is Farrington isn't it ?. I think i've ridden
train heading north through Farrington and the train set started to make a
loud 50Hz hum after that point.
 Do the trains change over in the station itself while stopped ?

 Farrington is easy to get to, although how well the station staff will
respond to some one standing there with a camera a photographing trains
instead of just hopping on the first one past I don't know.

 I'd also like to see one of the other voltage change points, which I
understand is Kensington Olympia. Where exactly is this point - at the
station I see on my London and Surounds street directory or some other
point along the line ?
 And if the change over point is visible from a near by road or the
station how frequently do the goods trains come through so that I could
see the electric locomotives transition from overhead to 3rd rail or vis ?
 (And is it the kind of area where you would hang around for a while
rather obviously carrying a camera ?)


 A side note, does any one produce a map of the British railway
network that shows the various electrification systems ?. On and off i've
tried to find a map that doesn't just show the lines but shows the
traction system - non electrified, overhead or 3rd rail. Nothing seems to
be online that shows the extent of the electrification.

"Matthew Geier"  wrote in message
news:pan.2005.08.07.21.33.16.127078@wibble.sleeper.apana.org.au...

>
>  I'm visiting London in a few weeks and being an 'electric train' kind of
> nut I'm interested in seeing the voltage change over points.
>
>  The Thameslink change over is Farrington isn't it ?. I think i've ridden
> train heading north through Farrington and the train set started to make a
> loud 50Hz hum after that point.
>  Do the trains change over in the station itself while stopped ?
>

It is while stopped in the station (actually Farringdon).

>
>  I'd also like to see one of the other voltage change points, which I
> understand is Kensington Olympia. Where exactly is this point - at the
> station I see on my London and Surounds street directory or some other
> point along the line ?


It's actually some distance north of Kensington Olympia. AIUI Class 313
trains (on the Clapham Junction - Willesden Junction shuttle) have to stop,
but Class 477 (on the Brighton - Watford Junction service), Eurostars, and
Class 92 freight locos can change over on the move.

IIRC North London Line trains from Richmond to North Woolwich change between
3rd rail DC and 25kV AC OHLE at Acton Central, Camden Road, Dalston
Kingsway, and Hackney Wick.

Peter

On Sun, 7 Aug 2005 21:51:02 +0000 (UTC), "Peter Masson"
 wrote:


>It's actually some distance north of Kensington Olympia. AIUI Class 313
>trains (on the Clapham Junction - Willesden Junction shuttle) have to stop,
>but Class 477 (on the Brighton - Watford Junction service), Eurostars, and
>Class 92 freight locos can change over on the move.


Whenever I've used an Electrostar on this route (that's about twice, I
think) it has stopped and powered down completely to change over.  A
full power-down-and-back-up appears to take a few minutes to complete.

Neil

-- 
Neil Williams in Milton Keynes, UK
When replying please use neil at the above domain
'wensleydale' is a spam trap and is not read.

> I'm visiting London in a few weeks and being an 'electric train' kind of
> nut I'm interested in seeing the voltage change over points.
>
> The Thameslink change over is Farrington isn't it ?. I think i've ridden
> train heading north through Farrington and the train set started to make a
> loud 50Hz hum after that point.
> Do the trains change over in the station itself while stopped ?
>
> Farrington is easy to get to, although how well the station staff will
> respond to some one standing there with a camera a photographing trains
> instead of just hopping on the first one past I don't know.
>
> I'd also like to see one of the other voltage change points, which I
> understand is Kensington Olympia. Where exactly is this point - at the
> station I see on my London and Surounds street directory or some other
> point along the line ?
> And if the change over point is visible from a near by road or the
> station how frequently do the goods trains come through so that I could
> see the electric locomotives transition from overhead to 3rd rail or vis ?
> (And is it the kind of area where you would hang around for a while
> rather obviously carrying a camera ?)
>
>
> A side note, does any one produce a map of the British railway
> network that shows the various electrification systems ?. On and off i've
> tried to find a map that doesn't just show the lines but shows the
> traction system - non electrified, overhead or 3rd rail. Nothing seems to
> be online that shows the extent of the electrification.


Years back when I used the North London Line between Stratford and Kentish 
Town West, I remember the thud of the pantograph going up, the crack of 
arcing electricity and a loud hum at Camden Road.

Yes it is Farringdon on Thameslink and I'm sure they won't mind you
taking photos (but ensure flash is off to be safe).

I think you're right about Kensington Olympia. I don't know the
specifics.

If you're interested in electric trains make sure you check out the
good old Mk1 Slam Door EMUs on SET before they are all scrapped, there
are very few left now. (Victoria is a good place, and you can at least
get to Bromley South on a Travelcard).

>
> A side note, does any one produce a map of the British railway
> network that shows the various electrification systems ?. On and off i've
> tried to find a map that doesn't just show the lines but shows the
> traction system - non electrified, overhead or 3rd rail. Nothing seems to
> be online that shows the extent of the electrification.
>


Try this:

http://bueker.net/trainspotting/maps_british-isles.php
http://bueker.net/trainspotting/maps_london-area.php
http://bueker.net/trainspotting/maps_central-england-area.php
http://bueker.net/trainspotting/maps_glasgow-edinburgh-area.php


Dave

Yorkie wrote:

> Yes it is Farringdon on Thameslink and I'm sure they won't mind you
> taking photos (but ensure flash is off to be safe).
>
> I think you're right about Kensington Olympia. I don't know the
> specifics.


Don't forget Drayton Park, the first changeover point of the lot.

Easy to observe in either direction.

Peter Masson wrote:

> "Matthew Geier"  wrote in
> message
> news:pan.2005.08.07.21.33.16.127078@wibble.sleeper.apana.org.au...
>>
>>  I'm visiting London in a few weeks and being an 'electric train'
>> kind of nut I'm interested in seeing the voltage change over
>> points.
>>
>>  The Thameslink change over is Farrington isn't it ?. I think i've
>> ridden train heading north through Farrington and the train set
>> started to make a loud 50Hz hum after that point.
>>  Do the trains change over in the station itself while stopped ?
>>
> It is while stopped in the station (actually Farringdon).
>>
>>  I'd also like to see one of the other voltage change points,
>> which I understand is Kensington Olympia. Where exactly is this
>> point - at the station I see on my London and Surounds street
>> directory or some other point along the line ?
>
> It's actually some distance north of Kensington Olympia.


I think it's just south of Mitre Bridge Junction.  If you go to
www.streetmap.co.uk and enter the postcode
   W10 6AT
in the search box, you will get a map with the approximate location of
the changeover point arrowed.  I'm not sure whether there is a good
viewing position there, and it's not the friendliest of places to hang
about.

Acton Central and Farringdon are OK for taking photos, but make sure you
don't use flash.

-- 
Richard J.
(to e-mail me, swap uk and yon in address)

I think that you mean Farringdon.  The changeover is made while the trains
are standing in the station.

The North London line has several changeover points.  The route runs from
Richmond, in West London, to North Woolwich, in East London.

Starting at Richmond, the line is electrified on both third and fourth rail
systems.  North London line trains take power from the outside rail and
return it through the running rails. London Underground's District line
trains take power from the outside rail and return the current through the
central, fourth, rail.  The District line and NLL part company after
Gunnersbury.  At the next station, South Acton, the 750 volt, dc, third ends
and 25,000 volt, ac, overhead begins.  The changeover is made in the
station.

At Willesden Junction station the NLL line passes over the West Coast Main
Line, WCML, electrified at 25,000 volt ac overhead and the parallel suburban
lines, which are electrified on both third and fourth rail systems.  There
is a link from the suburban lines to the NLL where the changeover may be
made.  There are no scheduled passenger services over this link.

At Camden Road, NLL passenger trains switch back to third rail.  From Camden
Road to Dalston Kingsland NLL trains run off the third rail.  The double
track passenger line on this section is paralleled by a goods line, part
double part single track, which is electrified on the 25,000 ac o/h system.

The goods and passenger lines merge just before Dalston Kingsland.  The line
from here to just beyond HackneyWick has both 750v dc third rail and 25,000v
ac o/h.  The drivers of NLL passenger trains usually switch to o/h on this
section.  After Hackney Wick, the NLL parts company with the o/h electrified
lines before Stratford station is is the third rail only to the terminus at
North Woolwich.

All changes between ac o/h and dc third rail are made while the trains are
standing at a station.

There is a service from the NLL platforms at Willesden Junction to Clapham
Junction.  This starts as 25,000v ac o/h at the north end, Willesden
Junction, and switches to 750v dc third rail before Kensington Olympia.
This changeover is usually made on the move.  The ac o/h does not extend
into Kensington Olympia station.

Dave Wilcox.

"Matthew Geier"  wrote in message
news:pan.2005.08.07.21.33.16.127078@wibble.sleeper.apana.org.au...

>
>  I'm visiting London in a few weeks and being an 'electric train' kind of
> nut I'm interested in seeing the voltage change over points.
>
>  The Thameslink change over is Farrington isn't it ?. I think i've ridden
> train heading north through Farrington and the train set started to make a
> loud 50Hz hum after that point.
>  Do the trains change over in the station itself while stopped ?
>
>  Farrington is easy to get to, although how well the station staff will
> respond to some one standing there with a camera a photographing trains
> instead of just hopping on the first one past I don't know.
>
>  I'd also like to see one of the other voltage change points, which I
> understand is Kensington Olympia. Where exactly is this point - at the
> station I see on my London and Surounds street directory or some other
> point along the line ?
>  And if the change over point is visible from a near by road or the
> station how frequently do the goods trains come through so that I could
> see the electric locomotives transition from overhead to 3rd rail or vis ?
>  (And is it the kind of area where you would hang around for a while
> rather obviously carrying a camera ?)
>
>
>  A side note, does any one produce a map of the British railway
> network that shows the various electrification systems ?. On and off i've
> tried to find a map that doesn't just show the lines but shows the
> traction system - non electrified, overhead or 3rd rail. Nothing seems to
> be online that shows the extent of the electrification.
>
>
>

DERWENT Re: British electrification - voltage change over points
 Sun, 7 Aug 2005 21:51:02 +0000 (UTC), "Peter Masson"
 


>
>"Matthew Geier"  wrote in message
>news:pan.2005.08.07.21.33.16.127078@wibble.sleeper.apana.org.au...
>>
>>  I'm visiting London in a few weeks and being an 'electric train' kind of
>> nut I'm interested in seeing the voltage change over points.
>>
>>  The Thameslink change over is Farrington isn't it ?. I think i've ridden
>> train heading north through Farrington and the train set started to make a
>> loud 50Hz hum after that point.
>>  Do the trains change over in the station itself while stopped ?
>>
>It is while stopped in the station (actually Farringdon).
>>
>>  I'd also like to see one of the other voltage change points, which I
>> understand is Kensington Olympia. Where exactly is this point - at the
>> station I see on my London and Surounds street directory or some other
>> point along the line ?
>
>It's actually some distance north of Kensington Olympia. AIUI Class 313
>trains (on the Clapham Junction - Willesden Junction shuttle) have to stop,
>but Class 477 (on the Brighton - Watford Junction service), Eurostars, and
>Class 92 freight locos can change over on the move.
>
>IIRC North London Line trains from Richmond to North Woolwich change between
>3rd rail DC and 25kV AC OHLE at Acton Central, Camden Road, Dalston
>Kingsway, and Hackney Wick.
>


You can also try Drayton Park for some 313 pan lowering action.

I don't think there are any bits of 6.25 kV left, but there might be
some voltage boundaries out in the third rail teritory.

You could also see the 4th to 3rd rail boundaries at Gunnerbury,
Wimbledon, East Putney, Farringdon (although the 4th rail isn't live),
Harrow & Wealdstone (or is it Watford Junction?)

There must be some 4th-25 kV OHL transitions in East London as well -
Barking perhaps.

PRAR
-- 
<http://www.i.am/prar/> and <http://prar.fotopic.net/>
As long as people will accept crap, it will be financially profitable to dispense it. --Dick Cavett
Please reply to the newsgroup. That is why it exists.
NB Anti-spam measures in force
 - If you must email me use the Reply to address and not prar@deadspam.com

"David Wilcox"  wrote in message
news:dd61me$48r$1@newsm1.svr.pol.co.uk...

>


<snip most of great message>


> At the next station, South Acton, the 750 volt, dc,
> third ends and 25,000 volt, ac, overhead begins.
> The changeover is made in the station.


Acton Central, I believe.


> The goods and passenger lines merge just before
> Dalston Kingsland.  The line from here to just beyond
> HackneyWick has both 750v dc third rail and 25,000v
> ac o/h.  The drivers of NLL passenger trains usually
> switch to o/h on this section.


I wonder why?

-- 
John Rowland - Spamtrapped
Transport Plans for the London Area, updated 2001
http://www.geocities.com/Athens/Acropolis/7069/tpftla.html
A man's vehicle is a symbol of his manhood.
That's why my vehicle's the Piccadilly Line -
It's the size of a county and it comes every two and a half minutes

"John Rowland"  a crit dans le
message de news:dd6joj$l0b$1$8302bc10@news.demon.co.uk...

> "David Wilcox"  wrote in message
> news:dd61me$48r$1@newsm1.svr.pol.co.uk...
> >
>
> <snip most of great message>
>
> > At the next station, South Acton, the 750 volt, dc,
> > third ends and 25,000 volt, ac, overhead begins.
> > The changeover is made in the station.
>
> Acton Central, I believe.
>
correct.

> > The goods and passenger lines merge just before
> > Dalston Kingsland.  The line from here to just beyond
> > HackneyWick has both 750v dc third rail and 25,000v
> > ac o/h.  The drivers of NLL passenger trains usually
> > switch to o/h on this section.
>
> I wonder why?
>

In the first instance, because there is a big board at the end of the
eastbound platform at Kingsland instructing them to do so (and another board
instructing them do to the opposite at the western end of the westbound
platform). That may be because:
- there is no other suitable place for motive power heading towards the
Graham Rd. chord to change-over
- no risk of 'gapping' or icing problems with 25 kV power
- less risk of galvanic effects if any stray return current paths
- AFAIK, more power is available with 25 kV supply.

Perhaps the question should be why 750 V dc supplies remain operational on
this section.

Regards,

- Alan (in Brussels)
PS - although not actually in London, there is also a 750 V dc /25 kV
changeover for Eurostars near Fawham junction, easily seen from the
overbridge (nearest station: Longfield).

In message , 
at 07:33:16 on Mon, 8 Aug 2005, Matthew Geier 
 remarked:

> The Thameslink change over is Farrington isn't it ?. I think i've ridden
>train heading north through Farrington and the train set started to make a
>loud 50Hz hum after that point.
> Do the trains change over in the station itself while stopped ?


Yes, but there is almost nothing to see. All that happens is that the 
OHL pantograph is gently raised or lowered (depending on which way the 
train is going).
-- 
Roland Perry

"Roland Perry"  wrote in message 
news:oUChbZKwLx9CFAeG@donald.internetpolicynews.co.uk...

> In message , 
> at 07:33:16 on Mon, 8 Aug 2005, Matthew Geier 
>  remarked:
>> The Thameslink change over is Farrington isn't it ?. I think i've ridden
>>train heading north through Farrington and the train set started to make a
>>loud 50Hz hum after that point.
>> Do the trains change over in the station itself while stopped ?
>
> Yes, but there is almost nothing to see. All that happens is that the OHL 
> pantograph is gently raised or lowered (depending on which way the train 
> is going).


In my experience, there's sometimes a bit of arcing visible and there's 
always a crackle and fizz as the pantograph touches. This is apparent even 
from inside the train.

Strangely, Farringdon is the only place where I'm aware of the changeover. 
I've never noticed the crackle and fizz of changeovers on the NLL line - or 
the WLL north of Kensington Olympia.

I've made a few trips on the Watford Jcn - Kensington Olympia - Clapham
Jcn line, and the changeover south of Mitre Bridge Jcn (it's near the
Eurostar depot) is quite noticeable when done on the move (especially
northbound) in a 319 - plenty of humming and a fizz as the pan makes
contact with the OLE.

In article <dd5vo6$cva$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com>,
   Peter Masson  wrote:

> It's actually some distance north of Kensington Olympia. AIUI Class 313
> trains (on the Clapham Junction - Willesden Junction shuttle) have to
> stop, but Class 477 (on the Brighton - Watford Junction service),
> Eurostars, and Class 92 freight locos can change over on the move.


The Watford trains are actually 377; they usually stop but I have, on a
couple of trips, gone straight through southbound - bu never northbound.

-- 
David Wild using RISC OS on broadband

In message <42f71da2$0$3499$ed2619ec@ptn-nntp-reader03.plus.net>, at 
09:53:49 on Mon, 8 Aug 2005, Martin Underwood  remarked:

>Strangely, Farringdon is the only place where I'm aware of the changeover.
>I've never noticed the crackle and fizz of changeovers on the NLL line - or
>the WLL north of Kensington Olympia.


It's "indoors", and the wire is quite close to the top of the carriage.

I'll take my hat off to anyone able to photograph the fizz, though.
-- 
Roland Perry

"David Wilcox"  wrote

>
> At Willesden Junction station the NLL line passes over the West Coast Main
> Line, WCML, electrified at 25,000 volt ac overhead and the parallel
suburban
> lines, which are electrified on both third and fourth rail systems.  There
> is a link from the suburban lines to the NLL where the changeover may be
> made.  There are no scheduled passenger services over this link.
>

The 0600 Willesden Jn LL to North Woolwich, and the 0613 Willesden Jn LL to
Stratford LL use the spur from the Watford New Line to the NLL, as do the
2257 (and the 2236SuO) North Woolwich to Willesden Jn LL.

Peter

Dave wrote:

> >
> > A side note, does any one produce a map of the British railway
> > network that shows the various electrification systems ?. On and off i've
> > tried to find a map that doesn't just show the lines but shows the
> > traction system - non electrified, overhead or 3rd rail. Nothing seems to
> > be online that shows the extent of the electrification.
> >
> Try this:
> http://bueker.net/trainspotting/maps_london-area.php


There's also a map in Baker's Rail Atlas showing which lines are
electrified, and on which system, but it's not very detailed. For
minute detail of exactly which piece of track is wired, and which
crossover, siding etc, you need Quail.

Trackmaps are republishing the Quail series of maps, using colour this
time, and identifying electrification systems. So far though, only the
"Midlands and North West" book has appeared. This does however cover
Euston, St Pancras, Farringdon, and much of the North London Line. GBP
12.95 from most transport bookshops, or go to
<http://www.trackmaps.co.uk/availablesoon.htm>.
-- 
Pat Ricroft, City of Salford, UK
================================

On Sun, 07 Aug 2005 23:06:01 +0100, Dave wrote:


>>
>> A side note, does any one produce a map of the British railway
>> network that shows the various electrification systems ?.

> Try this:
 
> http://bueker.net/trainspotting/maps_british-isles.php
> http://bueker.net/trainspotting/maps_london-area.php
> http://bueker.net/trainspotting/maps_central-england-area.php
> http://bueker.net/trainspotting/maps_glasgow-edinburgh-area.php


 I've spent ages typing various search terms into Google trying to find
something like these maps...

 Just what i'm after.

OK, a few, facts figures and info for this thread:

DC to AC and vice-versa changeovers in the UK:

Drayton Park
Farringdon
Acton Central
Mitre Bridge
Dollands Moor
Scrubbs Lane TSL
Woodyard Close TSL
Camden Road
Kingsland

Oever the years there have been many plans to rid the NLL of the DC
electrification, which incidentally is 650V DC, not 750V DC - many
historical reasons dating back to the original stock. However, the
civil works to get the OLE through the tunnels makes the scheme very
expensive.

The crackle and fizz you hear when the panto is raised is the HV
jumping a centimetre or so and is the charging current for the voltage
transformer mounted on the roof ahead of the main circuit breaker.

Richard

On 8 Aug 2005 09:50:07 -0700 someone who may be RBCatlow@aol.com
wrote this:-


>Oever the years there have been many plans to rid the NLL of the DC
>electrification, which incidentally is 650V DC, not 750V DC - many
>historical reasons dating back to the original stock. However, the
>civil works to get the OLE through the tunnels makes the scheme very
>expensive.


I would ask a different question Richard. Unless the whole of the DC
installation is/was removed, excepting that bit shared with
"underground" trains, is/was there much point in only removing
relatively short bits of the DC installation? While it improves
safety (and perhaps makes electrification and signalling easier) the
downside is several changes of system, something the British don't
seem too good at except in regard to the Channel Tunnel.

Would it not have been better to put up the AC system for the
passenger and freight trains that use it, while leaving the DC
system for those passenger trains that use it? Alternatively would
it not have made sense to spend the money to convert all the line
and the New Line to AC, leaving DC to a few sections shared with
"underground" trains?


-- 
 David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
 I will always explain revoked keys, unless the UK government
 prevents me by using the RIP Act 2000.

Thomas wrote:

>>I'm visiting London in a few weeks and being an 'electric train' kind of
>>nut I'm interested in seeing the voltage change over points.
>>
>>The Thameslink change over is Farrington isn't it ?. I think i've ridden
>>train heading north through Farrington and the train set started to make a
>>loud 50Hz hum after that point.
>>Do the trains change over in the station itself while stopped ?
>>

  snip

Isn't there also a change-over at Finsbury Park when trains go down the 
tunnel to Moorgate?


Dave

wrote

>
> Oever the years there have been many plans to rid the NLL of the DC
> electrification, which incidentally is 650V DC, not 750V DC - many
> historical reasons dating back to the original stock. However, the
> civil works to get the OLE through the tunnels makes the scheme very
> expensive.
>

It'll be possible to get rid of the Network Rail DC electrification at the
eastern end, when the NLL is cut back to Stratford HL and DLR takes over
Stratford International - Stratford LL - Canning Town (and later, if it
comes to pass, Crossrail takes over Custom House - Silvertown). It would
surely make sense for flexibility of operation to have all three tracks
electrified at 25kV OHLE between Dalston Kingsland and Camden Road. But from
Acton Central - Richmond means retaining 4th rail DC electrification for LUL
between Gunnersbury and Richmond. Would the answer here be dual
electrification, or is that now too difficult (i.e. expensive) for signal
immunisation, etc?

Peter

RBCatlow@aol.com wrote:

> Oever the years there have been many plans to rid the NLL of the DC
> electrification, which incidentally is 650V DC, not 750V DC - many
> historical reasons dating back to the original stock. However, the
> civil works to get the OLE through the tunnels makes the scheme very
> expensive.


Possibly not an issue as the Woolwich section is tipped for conversion
to DLR, but is it so that the electrification east of Dalston (?) is
very weak? There seems to be only one substation for the whole lot.

RBCatlow@aol.com wrote:

>
> DC to AC and vice-versa changeovers in the UK:
>
> Drayton Park
> Farringdon
> Acton Central
> Mitre Bridge
> Dollands Moor
> Scrubbs Lane TSL
> Woodyard Close TSL
> Camden Road
> Kingsland
>
> Oever the years there have been many plans to rid the NLL of the DC
> electrification, which incidentally is 650V DC, not 750V DC - many
> historical reasons dating back to the original stock. However, the
> civil works to get the OLE through the tunnels makes the scheme very
> expensive.


Adding to the multitude of postings just appearing.....

Sorry to nit-pick, and please correct me if I've got the wrong end of the
stick (which I probably have :-) ), but I didn't think there were any
significant tunnel sections of the NLL left.....?   I realise Hampstead
Tunnel got converted to AC a few years back, so I get the impression that
the remaining DC bits of the NLL are in open air (with the exception of
Connaught Tunnel which may eventually be used by Crossrail).

Also is there still a changeover in Watford Junction on the down fast?

Finally, when the ELL finally gets joined up to the NLL just west of
Dalston, will the ELL stock be dual-voltage or just DC?  If it's the latter
I assume that this bit of the NLL (to Canonbury) will have to remain
DC-capable.

Cheers
Angus

Peter Masson wrote:
 Would the answer here be dual

> electrification, or is that now too difficult (i.e. expensive) for signal
> immunisation, etc?


Dual electrification is an absolute no no. The systems are mutually
incompatible in that the AC system must be earthed, whereas the DC
system must be insulated from earth to prevent stray current corrosion.
Signalling immunisation isn't too much of a problem if you are prepared
to remove all DC or AC track circuits and detection and replace them
with modulated types such as HVIs, FS2600s and TI21s.

The latest thinking on the NLL is only to retain the DC at the western
end if the DLR take over the Stratford - N Woolwich section and thus
get shot of at least two voltage changeover points.

Richard

I can't remember the details now, but when the Graham Road Curve was
built there some serious complications caused by bringing together the
25Hz system on the Great Eastern and the d.c. one on the North London.
I seem to remember that some large resistances had to be installed in
trackside cabinets for some reason to resolve the problem.  Any
electrical engineers here know the details?

I'm sure that you could have long lengths of dual electrified line if
you wanted to, but I'm equally sure that it's something that the
engineers would want to avoid if at all possible.  The added
complication is going to lead to reduced reliability, and increased
costs.  It's probably easier, and cheaper, to do if you are installing
both systems, and replacing the entire signaling system, at the same
time, rather than adding an extra system to an existing railway.

Graham Road must have been another changeover point, but I assume that
anything which goes that way now stays on a.c.

Is there anywhere on Merseyside where a changeover could be made?
There's a short length of cunductor rail under the wires in platform 6
at Watford Junction, presumably used to get 313s onto a.c. for the trip
to Bletchley.

Stephen Furley wrote:

> I can't remember the details now, but when the Graham Road Curve was
> built there some serious complications caused by bringing together the
> 25Hz system on the Great Eastern and the d.c. one on the North London.
> I seem to remember that some large resistances had to be installed in
> trackside cabinets for some reason to resolve the problem.  Any
> electrical engineers here know the details?


Indeed, it was a very complex system engineered by David Bradley, who
wrote a very detailed article in MR sometime in 1988, describing it.
The resistances used were 1 ohm ceramic types rated at 100A continuous
and the stock going round the curve on DC had to do it in notch 1. The
recturn current busbars at Hackney Downs TSC had to be seperated by
resistances as well, splitting the installation into hackney Downs No1
and Hackney Downs No2


> I'm sure that you could have long lengths of dual electrified line if
> you wanted to.


Absolutely not, no way, no, no no. The incompatibility between the
earthing and earth free requirements of AC and DC systems make it a
complete nightmare. The dual electrified stretches at Ashford are
protected by pairs of isolating transformers at each end of each line
and the safety, corrosion and interference issues excercised myself and
some much brainier folk than I for over 18 months - horrendous and only
considered in extremis.


>
> Graham Road must have been another changeover point, but I assume that
> anything which goes that way now stays on a.c.

Yup.
>
> Is there anywhere on Merseyside where a changeover could be made?

No

> There's a short length of cunductor rail under the wires in platform 6
> at Watford Junction, presumably used to get 313s onto a.c. for the trip
> to Bletchley. 


Right again.


Richard

On Sun, 07 Aug 2005 23:54:17 +0100, PRAR  wrote:



>You could also see the 4th to 3rd rail boundaries at Gunnerbury,
>Wimbledon, East Putney, Farringdon (although the 4th rail isn't live),


Why is there 4th rail at Farringdon anyway? Did LU trains ever run
into these platforms?


>Harrow & Wealdstone (or is it Watford Junction?)


The 4th rail here still runs all the way to Watford Junction. I
believe there is, however, a 4th-to-3rd transition (now probably very
rusty) on the defunct Croxley Green branch. There's also one just
south of Kilburn High Road. And there might also be one (just
guessing) between Willesden Jn (low level) and Kensal Rise, if there
is a 3rd-rail-only section before the transition to OHLE.


>There must be some 4th-25 kV OHL transitions in East London as well -
>Barking perhaps.


I think the only connection between LU and NR here is a recently-built
one at Upminster.

asdf wrote:


> The 4th rail here still runs all the way to Watford Junction.


The 4th rail on the Watford line is bonded to the running rails, and
tube stock running on that section requires higher standard insulation
as a result.  This has been the case since the BR stock was converted
from 4th rail to 3rd rail operation in (IIRC) the late 1970s.

The 4th rail north of Harrow and Wealdstone is merely an additional
return path, and some sections are no longer on insulators.  In fact,
I'm pretty sure that at least one bit of 4th conductor has been
replaced with a length of FB rail.

In article <dd84fg$ii1$1$830fa7a5@news.demon.co.uk>,
   David Steele  wrote:

> Isn't there also a change-over at Finsbury Park when trains go down the 
> tunnel to Moorgate?


The changeover is actually in the platforms at Drayton Park.

-- 
David Wild using RISC OS on broadband

In article <dd851m$h95$1@gemini.csx.cam.ac.uk>,
   Angus Bryant  wrote:

> Sorry to nit-pick, and please correct me if I've got the wrong end of the
> stick (which I probably have :-) ), but I didn't think there were any
> significant tunnel sections of the NLL left.....?   I realise Hampstead
> Tunnel got converted to AC a few years back, so I get the impression that
> the remaining DC bits of the NLL are in open air (with the exception of
> Connaught Tunnel which may eventually be used by Crossrail).

> Also is there still a changeover in Watford Junction on the down fast?


Yes there is. There is just a very short section of third rail on Platform
6 to allow DC trains on to the 25000Kv system.

-- 
David Wild using RISC OS on broadband

RBCatlow@aol.com wrote:


> Absolutely not, no way, no, no no. The incompatibility between the
> earthing and earth free requirements of AC and DC systems make it a
> complete nightmare. The dual electrified stretches at Ashford are
> protected by pairs of isolating transformers at each end of each line
> and the safety, corrosion and interference issues excercised myself and
> some much brainier folk than I for over 18 months - horrendous and only
> considered in extremis.


Richard,

There's a considerable length, i.e. far more than just enough to do a
changeover, of dual electrified line from the junction of the No.1 and
No.2 lines East of Canonbury, through Dalston Kingsland, extending as
far as, I think, Channelsea South Junction.  If this can be done then
surely it would be technically *possible* to build a much longer one,
would it not?  In theory, if somebody wanted to build a dual
electrified line from, say, London to Brighton, and was prepared to
throw enough time, money and effort at the problem, could it not be
done?  Obviously, in the real world it never would be because, as you
say, it would be a 'complete nightmare', and 'horrendous', and the
costs would far exceed any possible advantage, but are the reasons not
those of economics and practicality, rather than technical possibility?
 Is it not a problem which is not worth solving, rather than one which
cannot be solved?

Now that the d.c. system has been removed from parts of the North
London Line, so that it can no longer be worked by d.c. only stock, why
has such a long dual electrified section not beed converted to a.c.
only?

With dual Voltage stock now being much more common than it used to be,
I think the chances of anything more than the length required for a
changeover of dual electrified line being built in future are just
about nil.

RBCatlow@aol.com wrote:


> Absolutely not, no way, no, no no. The incompatibility between the
> earthing and earth free requirements of AC and DC systems make it a
> complete nightmare. The dual electrified stretches at Ashford are
> protected by pairs of isolating transformers at each end of each line
> and the safety, corrosion and interference issues excercised myself and
> some much brainier folk than I for over 18 months - horrendous and only
> considered in extremis.


Richard,

There's a considerable length, i.e. far more than just enough to do a
changeover, of dual electrified line from the junction of the No.1 and
No.2 lines East of Canonbury, through Dalston Kingsland, extending as
far as, I think, Channelsea South Junction.  If this can be done then
surely it would be technically *possible* to build a much longer one,
would it not?  In theory, if somebody wanted to build a dual
electrified line from, say, London to Brighton, and was prepared to
throw enough time, money and effort at the problem, could it not be
done?  Obviously, in the real world it never would be because, as you
say, it would be a 'complete nightmare', and 'horrendous', and the
costs would far exceed any possible advantage, but are the reasons not
those of economics and practicality, rather than technical possibility?
 Is it not a problem which is not worth solving, rather than one which
cannot be solved?

Now that the d.c. system has been removed from parts of the North
London Line, so that it can no longer be worked by d.c. only stock, why
has such a long dual electrified section not beed converted to a.c.
only?

With dual Voltage stock now being much more common than it used to be,
I think the chances of anything more than the length required for a
changeover of dual electrified line being built in future are just
about nil.

"asdf" <invalid@invalid.invalid> wrote

>
> The 4th rail here still runs all the way to Watford Junction.


AIUI operation is 3rd rail from Harrow to Watford. The 4th rail is probably
electrically bonded to the running rails for the return path.

Peter

25000Kv!  25 kV, surely  :)

"Stephen Furley"  wrote


> With dual Voltage stock now being much more common than it used to be,
> I think the chances of anything more than the length required for a
> changeover of dual electrified line being built in future are just
> about nil.
>

AIUI the 'keep on switching between ac and dc' on the NLL came about because
the OHLE has always been provided by other users of the railway. Camden
Road - Dalston Kingsland (via the reversible freight line) and on to
Channelsea was fitted with OHLE for freight, while Mitre Bridge - Camden
Road, and on to the ECML via the North London incline was converted
primarily for NoL E*. Willesden Junction to Acton Central was added in to
reach a more suitable changeover point.

Peter

Stephen Furley wrote:


>
> There's a considerable length, i.e. far more than just enough to do a
> changeover, of dual electrified line from the junction of the No.1 and
> No.2 lines East of Canonbury, through Dalston Kingsland, extending as
> far as, I think, Channelsea South Junction.


Plus, of course, the section down Camden Bank and into the suburban
platforms at Euston.  That really must be interesting to maintain,
particularly as it has been converted from 4th to 3rd rail, and is in a
complex area.

Stephen Furley wrote:


>
> There's a considerable length, i.e. far more than just enough to do a
> changeover, of dual electrified line from the junction of the No.1 and
> No.2 lines East of Canonbury, through Dalston Kingsland, extending as
> far as, I think, Channelsea South Junction.


Plus, of course, the section down Camden Bank and into the suburban
platforms at Euston.  That really must be interesting to maintain,
particularly as it has been converted from 4th to 3rd rail, and is in a
complex area.

Stephen Furley wrote:


>
> There's a considerable length, i.e. far more than just enough to do a
> changeover, of dual electrified line from the junction of the No.1 and
> No.2 lines East of Canonbury, through Dalston Kingsland, extending as
> far as, I think, Channelsea South Junction.


Plus, of course, the section down Camden Bank and into the suburban
platforms at Euston.  That really must be interesting to maintain,
particularly as it has been converted from 4th to 3rd rail, and is in a
complex area.

"Matthew Geier"  wrote in message 
news:pan.2005.08.08.13.01.44.247737@wibble.sleeper.apana.org.au...

> On Sun, 07 Aug 2005 23:06:01 +0100, Dave wrote:
>
>>>
>>> A side note, does any one produce a map of the British railway
>>> network that shows the various electrification systems ?.
>
>> Try this:
>
>> http://bueker.net/trainspotting/maps_british-isles.php
>> http://bueker.net/trainspotting/maps_london-area.php
>> http://bueker.net/trainspotting/maps_central-england-area.php
>> http://bueker.net/trainspotting/maps_glasgow-edinburgh-area.php
>
> I've spent ages typing various search terms into Google trying to find
> something like these maps...
>
> Just what i'm after.
>
>


I was looking for something similar a while back, but was in the same boat 
as you and all but forgot about it. Then around January a conversation came 
up on m.t.r.e about Spain and someone posted the Spanish version of that 
map. A few weeks later it crossed my mind to backtrack the URL and sure 
enough there were maps covering the whole of Europe. Your question jogged my 
memory...

Not sure why the entry pages don't index properly.

Dave

Upon the miasma of midnight, a darkling spirit identified as Stephen 
Furley  gently breathed:

>25000Kv!  25 kV, surely  :)


I'd like to see the unit that ran on 25,000kV!  I'd like to see how far 
above the carriage roofs the wire had to be too...

:-)

-- 
  - Pyromancer Stormshadow.
http://www.inkubus-sukkubus.co.uk   <-- Pagan Gothic Rock!
http://www.littlematchgirl.co.uk    <-- Electronic Metal!
http://www.revival.stormshadow.com  <-- The Gothic Revival.

Stephen Furley wrote:


>
> There's a considerable length, i.e. far more than just enough to do a
> changeover, of dual electrified line from the junction of the No.1 and
> No.2 lines East of Canonbury, through Dalston Kingsland, extending as
> far as, I think, Channelsea South Junction.


Plus, of course, the section down Camden Bank and into the suburban
platforms at Euston.  That really must be interesting to maintain,
particularly as it has been converted from 4th to 3rd rail, and is in a
complex area.

> >
> > Is there anywhere on Merseyside where a changeover could be made?
>
> No

There is. The up and down electric line from Hunts Cross West to a
point just before Hunts Cross station has 3rd rail and 25kv overhead.So
in theory a 313 could come from Allerton junc on the 25Kv overhead drop
on to the Electic line Change ends and switch to 3rd rail running and
run onto the Merseyrail Northen Line.

In article ,
   asdf <invalid@invalid.invalid> wrote:

> >Harrow & Wealdstone (or is it Watford Junction?)

> The 4th rail here still runs all the way to Watford Junction.


Not now, it doesn't. There are several gaps where the centre conductor has
been removed.

-- 
David Wild using RISC OS on broadband

In article ,
   Stephen Furley  wrote:

> 25000Kv!  25 kV, surely  :)

It depends on the weather. :-))

-- 
David Wild using RISC OS on broadband

wrote in message 
news:1123524463.055361.59080@z14g2000cwz.googlegroups.com...

>
> Stephen Furley wrote:
>> I can't remember the details now, but when the Graham Road Curve was
>> built there some serious complications caused by bringing together the
>> 25Hz system on the Great Eastern and the d.c. one on the North London.
>> I seem to remember that some large resistances had to be installed in
>> trackside cabinets for some reason to resolve the problem.  Any
>> electrical engineers here know the details?
>
> Indeed, it was a very complex system engineered by David Bradley, who
> wrote a very detailed article in MR sometime in 1988, describing it.
> The resistances used were 1 ohm ceramic types rated at 100A continuous
> and the stock going round the curve on DC had to do it in notch 1. The
> recturn current busbars at Hackney Downs TSC had to be seperated by
> resistances as well, splitting the installation into hackney Downs No1
> and Hackney Downs No2


25 Hz? Do some 25 kV systems use 25 Hz rather than 50 Hz? If so, how is this 
generated from the 50 Hz National Grid feed?

On Mon, 08 Aug 2005 12:15:28 -0700, Stephen Furley wrote:


> 
> RBCatlow@aol.com wrote:
> 
>> Absolutely not, no way, no, no no. The incompatibility between the
>> earthing and earth free requirements of AC and DC systems make it a
>> complete nightmare. The dual electrified stretches at Ashford are
>> protected by pairs of isolating transformers at each end of each line
>> and the safety, corrosion and interference issues excercised myself and
>> some much brainier folk than I for over 18 months - horrendous and only
>> considered in extremis.



 But does the problem have to solved from scratch each time ?. Once you
have a system worked out, is each location so different that it requires
lots of new work each time ?



> would it not?  In theory, if somebody wanted to build a dual electrified
> line from, say, London to Brighton, and was prepared to throw enough
> time, money and effort at the problem, could it not be done? 


 As they are currently throwing lots of money at the 3rd rail system due
to it's inablity to run new high power trains with high power
air-conditioning, I always thought that what they should do is commit to
long term re-electrification to AC, make ALL new EMU stock dual voltage
and dual electrify the poorly supplied sections on the DC network with 25k
overhead, with the new trains switching on the fly to the AC supply where
available.

 Over time, the DC only stock disappears and you disconnect the 3rd rail
in those areas and slowly convert more and more over as the DC system
either needs reinforcement or becomes 'life expired'.

 Interestingly the Dutch seem to have made a long term commitment to
convert from 1500DC overhead to 25KAC overhead and now all new rolling
stock is dual or easily convertable and all new OHL work is done in such
a way to be AC compatable. Could take them 20 years, but if you make sure
all new stock is compatable with such a plan, and just work at it slowly
over a long period.

 The only real problem I can see with converting the DC lines to overhead
are the nearby NIMBYs complaining about the 'visual pollution' caused by
the addition of overhead wires and the masts to the railway.

RBCatlow@aol.com wrote:


> Absolutely not, no way, no, no no. The incompatibility between the
> earthing and earth free requirements of AC and DC systems make it a
> complete nightmare. The dual electrified stretches at Ashford are
> protected by pairs of isolating transformers at each end of each line
> and the safety, corrosion and interference issues excercised myself and
> some much brainier folk than I for over 18 months - horrendous and only
> considered in extremis.


Richard,

There's a considerable length, i.e. far more than just enough to do a
changeover, of dual electrified line from the junction of the No.1 and
No.2 lines East of Canonbury, through Dalston Kingsland, extending as
far as, I think, Channelsea South Junction.  If this can be done then
surely it would be technically *possible* to build a much longer one,
would it not?  In theory, if somebody wanted to build a dual
electrified line from, say, London to Brighton, and was prepared to
throw enough time, money and effort at the problem, could it not be
done?  Obviously, in the real world it never would be because, as you
say, it would be a 'complete nightmare', and 'horrendous', and the
costs would far exceed any possible advantage, but are the reasons not
those of economics and practicality, rather than technical possibility?
 Is it not a problem which is not worth solving, rather than one which
cannot be solved?

Now that the d.c. system has been removed from parts of the North
London Line, so that it can no longer be worked by d.c. only stock, why
has such a long dual electrified section not beed converted to a.c.
only?

With dual Voltage stock now being much more common than it used to be,
I think the chances of anything more than the length required for a
changeover of dual electrified line being built in future are just
about nil.

On Tue, 09 Aug 2005 07:51:05 +1000, Matthew Geier
 wrote:


>make ALL new EMU stock dual voltage


Isn't the newer third rail stock (Electrostar, Desiro, Juniper) fairly
easy to convert if the need arises by sticking a pantograph in the
hole on the roof and tweaking the software etc? There are examples of
each type with one, the other or (except Junipers?) both voltages out
there.  

Converting a Pendolino for DC could be trickier :-)


-- 
Arthur Figgis                Surrey, UK

On 8 Aug 2005 10:38:11 -0700, RBCatlow@aol.com wrote:


>Dual electrification is an absolute no no. 


I've heard that before - but there are a few bits of Merseyrail where
both exist, such as around the Allerton junctions, as well as several
platforms at Euston (as I recall).

Is there some complicated switching going on there?

Neil

-- 
Neil Williams in Milton Keynes, UK
When replying please use neil at the above domain
'wensleydale' is a spam trap and is not read.

On 8 Aug 2005 10:56:32 -0700, "Stephen Furley"
 wrote:


>Is there anywhere on Merseyside where a changeover could be made?


Maybe, but I couldn't say for certain if it'd be of any use to get
anywhere, at Allerton Junction.  That's the only bit I can think of -
the rest of the lines the system interfaces with are diesel.

Neil

-- 
Neil Williams in Milton Keynes, UK
When replying please use neil at the above domain
'wensleydale' is a spam trap and is not read.

David Wilcox wrote:


> 
> There is a service from the NLL platforms at Willesden Junction to Clapham
> Junction.  This starts as 25,000v ac o/h at the north end, Willesden
> Junction, and switches to 750v dc third rail before Kensington Olympia.
> This changeover is usually made on the move. 


Whenever I've got on that service (or walked past the changeover point, 
which is next to Scrubs Lane) the train has stopped for the changeover, 
it only takes about 30 seconds and IIRC it co-incides with a set of 
points so often the train has to stop there anyway

Stephen Furley wrote:

>
> There's a considerable length, i.e. far more than just enough to do a
> changeover, of dual electrified line from the junction of the No.1 and
> No.2 lines East of Canonbury, through Dalston Kingsland, extending as
> far as, I think, Channelsea South Junction.  If this can be done then
> surely it would be technically *possible* to build a much longer one,
> would it not?  In theory, if somebody wanted to build a dual
> electrified line from, say, London to Brighton, and was prepared to
> throw enough time, money and effort at the problem, could it not be
> done?  Obviously, in the real world it never would be because, as you
> say, it would be a 'complete nightmare', and 'horrendous', and the
> costs would far exceed any possible advantage, but are the reasons not
> those of economics and practicality, rather than technical possibility?


Indeed, there is a dual electrified strecth as you describe, the DC
system is very weak, hence the 3 and 6 cat formations which use it, as
opposed to more powerful types. There are no precautions taken to
prevent stray current corrosion and this has caused problems with the
structures, cables and utilities on the line. It would not meet any of
the present requirements for the control of corrosion, nor signalling
immunisation and as such it (together with the Euston - Watford
stretches of dual electrification) would never be considered today.

Sure if some complete dolts wanted to build a dual electrified railway
for miles and miles, it could be done, but the costs, complexity,
ongoing maintenance and so on would render it completely unviable. It's
also quite interesting if you get a 25kV short onto the con rail. Once
the smoke and fire subside, you fill in the form for all of the new
equipment needed!


>
> Now that the d.c. system has been removed from parts of the North
> London Line, so that it can no longer be worked by d.c. only stock, why
> has such a long dual electrified section not beed converted to a.c.
> only?


It has been on the drawing board for some time and the railway would
dearly love to get shot of the DC along the NLL west of Kingsland.
Watch the press, it may just happen.


>
> With dual Voltage stock now being much more common than it used to be,
> I think the chances of anything more than the length required for a
> changeover of dual electrified line being built in future are just
> about nil.


I'd agree

Richard

Whoops, 25Hz should have read 25kV.

In article , 
Chippy  writes

>Plus, of course, the section down Camden Bank and into the suburban
>platforms at Euston.  That really must be interesting to maintain,
>particularly as it has been converted from 4th to 3rd rail, and is in a
>complex area.


Thinking about it, 4th rail plus AC may well be *easier* to handle than 
3rd rail plus AC, because there needn't be any electrical connection 
between the two systems.

-- 
Clive D.W. Feather                       | Home: 
Tel: +44 20 8495 6138 (work)             | Web:  <http://www.davros.org>
Fax: +44 870 051 9937                    | Work: 
Please reply to the Reply-To address, which is:

Martin Underwood wrote:

>  wrote in message 
> news:1123524463.055361.59080@z14g2000cwz.googlegroups.com...
> 
>>Stephen Furley wrote:
>>
>>>I can't remember the details now, but when the Graham Road Curve was
>>>built there some serious complications caused by bringing together the
>>>25Hz system on the Great Eastern and the d.c. one on the North London.
>>>I seem to remember that some large resistances had to be installed in
>>>trackside cabinets for some reason to resolve the problem.  Any
>>>electrical engineers here know the details?
>>
>>Indeed, it was a very complex system engineered by David Bradley, who
>>wrote a very detailed article in MR sometime in 1988, describing it.
>>The resistances used were 1 ohm ceramic types rated at 100A continuous
>>and the stock going round the curve on DC had to do it in notch 1. The
>>recturn current busbars at Hackney Downs TSC had to be seperated by
>>resistances as well, splitting the installation into hackney Downs No1
>>and Hackney Downs No2
> 
> 
> 25 Hz? Do some 25 kV systems use 25 Hz rather than 50 Hz? If so, how is this 
> generated from the 50 Hz National Grid feed? 


Not the answer you were looking for, but in the US there were (are?) 
parts of the North East Corridor electrified at 25 Hz.  They rely(ied) 
upon their own independent supply system a la the German 16.7 Hz system.

Robin

Stephen Furley wrote:

> RBCatlow@aol.com wrote:
> 
> 
>>Absolutely not, no way, no, no no. The incompatibility between the
>>earthing and earth free requirements of AC and DC systems make it a
>>complete nightmare. The dual electrified stretches at Ashford are
>>protected by pairs of isolating transformers at each end of each line
>>and the safety, corrosion and interference issues excercised myself and
>>some much brainier folk than I for over 18 months - horrendous and only
>>considered in extremis.
> 
> 
> Richard,
> 
> There's a considerable length, i.e. far more than just enough to do a
> changeover, of dual electrified line from the junction of the No.1 and
> No.2 lines East of Canonbury, through Dalston Kingsland, extending as
> far as, I think, Channelsea South Junction.  If this can be done then
> surely it would be technically *possible* to build a much longer one,
> would it not?  In theory, if somebody wanted to build a dual
> electrified line from, say, London to Brighton, and was prepared to
> throw enough time, money and effort at the problem, could it not be
> done?  Obviously, in the real world it never would be because, as you
> say, it would be a 'complete nightmare', and 'horrendous', and the
> costs would far exceed any possible advantage, but are the reasons not
> those of economics and practicality, rather than technical possibility?
>  Is it not a problem which is not worth solving, rather than one which
> cannot be solved?


I'd have thought the use of axle counters would help solve a lot of the 
signalling issues with dual electrification.  There's still the stray 
current earthing problem, though.

Robin

In article ,
   Neil Williams  wrote:

> >Dual electrification is an absolute no no. 

> I've heard that before - but there are a few bits of Merseyrail where
> both exist, such as around the Allerton junctions, as well as several
> platforms at Euston (as I recall).


Platforms 9 and 10 at Euston have both third rail and overhead, as do the
slow lines on Camden bank.

-- 
David Wild using RISC OS on broadband

Thanks for the correction Richard; I did, of course, mean 25kV, 50Hz.

Martin, the only low frequency systems in this country were the LBSC
system from London Bridge to Victoria and down to Coulsdon North etc.,
and the Midland (I think) ine between Lancaster, Morecambe and Heysham;
both converted to other systems long ago, and the Heysham line since
de-electrified.  There are still some low frequency systems operating
in other countries.  In early days the railways generally had their own
power stations, so they could generate the required frequency directly,
later rotary converters were used to convert the frequency, and today
it can be done electronically.

There was a hand-painted warning of 25000 kV cables along the trackside
somewhere on the North London, near Camden Road, I think.  I'd like to
see the insulators required!

On Mon, 8 Aug 2005 22:26:30 +0100 someone who may be "Martin
Underwood"  wrote this:-


>25 Hz? Do some 25 kV systems use 25 Hz rather than 50 Hz?


Not any more. It was used a long time ago for a few lines and some
railway distribution systems.




-- 
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 I will always explain revoked keys, unless the UK government
 prevents me by using the RIP Act 2000.

On 8 Aug 2005 11:07:43 -0700 someone who may be RBCatlow@aol.com
wrote this:-


>Absolutely not, no way, no, no no. The incompatibility between the
>earthing and earth free requirements of AC and DC systems make it a
>complete nightmare.


Is there a difference between three and four rail systems in this
respect Richard?


-- 
 David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
 I will always explain revoked keys, unless the UK government
 prevents me by using the RIP Act 2000.

"Stephen Furley"  wrote:


>There was a hand-painted warning of 25000 kV cables along the trackside
>somewhere on the North London, near Camden Road, I think.  I'd like to
>see the insulators required!



Occasionally, you will see a model railway (at a show) with a warning
sign stating: 

DANGER - 12,000 mV

;-)

Clive D. W. Feather wrote:

> In article ,
> Chippy  writes
> >Plus, of course, the section down Camden Bank and into the suburban
> >platforms at Euston.  That really must be interesting to maintain,
> >particularly as it has been converted from 4th to 3rd rail, and is in a
> >complex area.
>
> Thinking about it, 4th rail plus AC may well be *easier* to handle than
> 3rd rail plus AC, because there needn't be any electrical connection
> between the two systems.


At first sight it would seem so.

I'd be interested to know what the situation is regarding inducted
currents in conductor rails.  After all, if the OLE can induce several
thousand volts in an isolated but not earthed wire over an adjacent
line, one would expect some similar effect in a conductor rail.  This
would presumably apply to both rails in a 4th rail system.

On Mon, 08 Aug 2005 23:21:49, Arthur Figgis 
wrote:

>
>Converting a Pendolino for DC could be trickier :-)


Indeed it would.  "Disgusted of Tunbridge Wells" et al would write
umpteen letters to The Times complaining about them!  ;-)

Paul Harley

-- 
Remove "eeek" to contact me!

Upon the miasma of midnight, a darkling spirit identified as Paul Harley
 gently breathed:

>On Mon, 08 Aug 2005 23:21:49, Arthur Figgis 
>wrote:

>>Converting a Pendolino for DC could be trickier :-)

>Indeed it would.  "Disgusted of Tunbridge Wells" et al would write
>umpteen letters to The Times complaining about them!  ;-)


I thought it was "Disgusted of Hove", and he already had?

-- 
 - Pyromancer Stormshadow.
http://www.inkubus-sukkubus.co.uk   <-- Pagan Gothic Rock!
http://www.littlematchgirl.co.uk    <-- Electronic Metal!
http://www.revival.stormshadow.com  <-- The Gothic Revival.

To be fair, the Dutch use overhead lines not a third rail, so it is a
lot easier to increase the electrical clearances required to operate at
25 kV overhead as opposed to 1500 V dc overhead, as was shown many
years ago when the lines from Liverpool Street (and in more recent
times Manchester - Hadfield) were converted. In any case, I believe
(can anyone confirm?) that the Dutch have got cold feet at the cost of
conversion to 25 kV and it is unlikely to happen for a long time.

To convert the Southern Region (as was) to 25 kV would be a very
expensive business as it would be necessary to increase clearances in
the many cuttings and tunnels that exist by about two to three feet.
Bear also in mind that many tunnels on the Southern run through chalk,
not an easy material to tunnel in.

In addition, the transition from DC to AC would require a number of new
changeovers and as has been described on this thread, these are not
simple to provide.

It would also be necessary to consider the effects on the National Grid
as at present the DC power supply is taken from the Grid (or
Distribution Network Operator) typically at 132 kV at sites around the
Region and stepped down to 33 kV (sometimes 22 or 11 kV) and cabled
along the track to the substations. (This is why it is usual to see two
concrete troughing runs by the trackside - one for traction power and
one for signalling). The Grid/DNO supply points have been selected both
to optimise the supply to the railway and to optimise the loading on
the Grid. Replacing 750 V dc with 25 kV ac would mean that the entire
traction power supply system would also have to be redesigned, as an ac
system would need more 132/25 kV feeder stations than the present
system and in many of the more rural areas, there is no suitable
transmission line available. In addition, this would result in changing
load patterns on the Grid, which may require strengthening in some
areas.

So, all in all, a non-starter.

yyOn 8 Aug 2005 10:38:11 -0700, RBCatlow@aol.com wrote:


>
>Peter Masson wrote:
> Would the answer here be dual
>> electrification, or is that now too difficult (i.e. expensive) for signal
>> immunisation, etc?
>
>Dual electrification is an absolute no no. The systems are mutually
>incompatible in that the AC system must be earthed, whereas the DC
>system must be insulated from earth to prevent stray current corrosion.


The 3rd-rail supply on the DC line and NLL is earthed on the negative
side of the supply; it is the LU 4-rail system which is nominally not
earthed (but actually loosely tied to earth via a resistor network
with monitoring circuits used to detect any full earth contacts).
Electrical supplies are generally required to have one side of the
supply connected to earth unless further precautions are taken or the
results of earth leakage are minimised by other means or
characteristics of the supply. The use of unearthed power supplies is
generally deprecated due to the variable and possibly disastrous
results of coming into contact with other supplies or the reduced
opportunity for protection against unintentional contact by people or
animals.
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

On Tue, 23 Aug 2005 17:38:56 +0000 (UTC) someone who may be "Peter
Masson"  wrote this:-


>Most of Southern's (i.e the former LB&SCR) suburban network used to be
>electrified at 6.6kV AC OHLE. If it was possible between 1909 and 1929 it
>ought to be possible now, even at the current standard voltage.


I'm glad you reminded us of this. I suspect that current clearances
around energised parts are a bit less than they were in 1909. The
insulators were smaller on the LBSCR but other clearances are quite
small now, as people have got to know electricity better.


-- 
 David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
 I will always explain revoked keys, unless the UK government
 prevents me by using the RIP Act 2000.

On Tue, 23 Aug 2005 20:54:23 +0100, David Hansen  
 wrote:


> On Tue, 23 Aug 2005 17:38:56 +0000 (UTC) someone who may be "Peter
> Masson"  wrote this:-
>
>> Most of Southern's (i.e the former LB&SCR) suburban network used to be
>> electrified at 6.6kV AC OHLE. If it was possible between 1909 and 1929  
>> it
>> ought to be possible now, even at the current standard voltage.
>
> I'm glad you reminded us of this. I suspect that current clearances
> around energised parts are a bit less than they were in 1909. The
> insulators were smaller on the LBSCR but other clearances are quite
> small now, as people have got to know electricity better.


Dont forget that in 1909 most of this area would have been rural. I  
suspect that most of the overbridges have been built since conversion to  
dc.

I cant really see much advantage in converting the Southern to AC given  
the nature of the services run, i think dc is actually a more reliable  
system.

paul



-- 
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

>I cant really see much advantage in converting the Southern to AC given
>the nature of the services run, i think dc is actually a more reliable
>system.



Gawd, imagine the chaos of the wires falling off every day added to the
existing scope for knock-on effects in this web of intensely operated
routes.

On Tue, 23 Aug 2005 16:36:43 +0100, Terry Harper
 wrote:


>Bearing in mind the clearance at Farringdon, and the possibility of
>dropping the floor of tunnels, it ought not to be too difficult.
>Changing to double-deck trains is the hard bit.


I remain to be convinced that DD is an appropriate solution to the
UK's problem, or indeed to the problem that Germany thinks it has when
it actually hasn't, that causes it to buy more of the damned things.

Neil

-- 
Neil Williams in Milton Keynes, UK
When replying please use neil at the above domain
'wensleydale' is a spam trap and is not read.

"paul Hutchinson"  wrote in message
news:op.svza4buxo3mvp0@paul-nn189bzj1r...

> On Tue, 23 Aug 2005 20:54:23 +0100, David Hansen
>  wrote:
>
> > On Tue, 23 Aug 2005 17:38:56 +0000 (UTC) someone who may be "Peter
> > Masson"  wrote this:-
> >
> >> Most of Southern's (i.e the former LB&SCR) suburban network used to be
> >> electrified at 6.6kV AC OHLE. If it was possible between 1909 and 1929
> >> it
> >> ought to be possible now, even at the current standard voltage.
> >
> > I'm glad you reminded us of this. I suspect that current clearances
> > around energised parts are a bit less than they were in 1909. The
> > insulators were smaller on the LBSCR but other clearances are quite
> > small now, as people have got to know electricity better.
>
> Dont forget that in 1909 most of this area would have been rural. I
> suspect that most of the overbridges have been built since conversion to
> dc.
>

ITYF that the lines included in the LBSCR AC electrification ran through
areas which were fully built up by the time the wires were put up. The
Greater London volume of 'A Regional History of the Railways of Greater
London' includes a map showing that the built up area extended to Purley in
1914. Coulsdon North and Sutton weren't wired until 1925, by when these
areas would have been built up.

Peter

Peter

On Tue, 23 Aug 2005 21:56:25 +0100 someone who may be "paul
Hutchinson"  wrote this:-


>Dont forget that in 1909 most of this area would have been rural.


Not the bits that were electrified on the AC system.


>I  
>suspect that most of the overbridges have been built since conversion to  
>dc.


I suspect that most were there before AC electrification, but this
is only a suspicion.


>I cant really see much advantage in converting the Southern to AC given  
>the nature of the services run, i think dc is actually a more reliable  
>system.


The advantages would be in terms of safety, ease of working on the
line and bad weather reliability. Some of these advantages could be
gained with a protected conductor rail and thought was given to this
before the 1967 Bournemouth electrification. It would have meant
other complications, but a slow transition to a protected conductor
rail would then have been possible.




-- 
 David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
 I will always explain revoked keys, unless the UK government
 prevents me by using the RIP Act 2000.

Considering some of the points raised:

1. The LBSCR's system only went as far out as Coulsdon North and Sutton
and did not run through any long tunnels. Lowering track through
tunnels is a costly and difficult business, especially when they run
through chalk, a material prone to falls. Bear in mind that it took 12
months to open out Higham and Strood tunnels to line them (previously
they had been unlined). A similar blockade would probably be necessary
on each and every major tunnel on the Brighton and South Eastern lines,
eg Quarry, Merstham, Clayton, Polhill, Sevenoaks, with consequent major
disruption.

2. The LBSCR had to leave frequent neutral sections in areas of
restricted clearance (source, "Southern Electric 1909-79" by G T
Moody), which would probably not be permissible today. Although neutral
sections are necessary on a 25 kV AC system, their number is optimised
to a minimum.

3. Third rail DC systems (and overhead DC systems such as tramways) are
NOT directly earthed. If they were, the traction return current would
leave the running rails (causing electrolytic corrosion to the rail at
the point where it did so) and then try to find some buried conductive
material such as a pipe to flow along back to its substation, thence
causing more corrosion when it leaves the conductor to flow back to the
substation. If you can get near a Southern substation (without
trespassing, of course), you will see the negative busbar is raised on
insulators and has no direct connection to earth. On the Tyne and Wear
Metro, the OHLE structures are mounted on insulated bases and then
bonded to the running rails for the same reason.

The system is a historical compromise, in that the resistance between
the running rails and earth via the sleepers and ballast is
sufficiently high to minimise the risk of stray currents and
sufficiently low to ensure that the risk of an electric shock from
anyone touching both the rail (or anything metallic connected to it)
and anything connected directly to earth is as low as reasonably
practicable. If you look at tram tracks, where the rails are set in the
street, the rails are often set in rubber or some other insulating
material to minimise stray current corrosion.

Stray current corrosion, as mentioned elsewhere on this thread, is a
serious problem, hence the difficulties associated with dual AC/DC
electrification.

To restate, there are no engineering reasons why the Southern could not
be converted to AC, but the cost and logistics of it and the resulting
severe disruption over many years mean that even if the money was
available, it would better be spent elsewhere. It's like changing the
rule of the road in UK to driving on the right - simple in theory but
in practice, the logistics and likely increase in the number of road
accidents make it a non-starter. (When Sweden changed in 1967, there
was a significant increase in the number of fatal RTAs for many years
afterwards.)

yyOn 24 Aug 2005 12:58:48 -0700,
billetelic_ferroequinologist@hotmail.com wrote:


>
>3. Third rail DC systems (and overhead DC systems such as tramways) are
>NOT directly earthed. If they were, the traction return current would
>leave the running rails (causing electrolytic corrosion to the rail at
>the point where it did so) and then try to find some buried conductive
>material such as a pipe to flow along back to its substation, thence
>causing more corrosion when it leaves the conductor to flow back to the
>substation. If you can get near a Southern substation (without
>trespassing, of course), you will see the negative busbar is raised on
>insulators and has no direct connection to earth. On the Tyne and Wear
>Metro, the OHLE structures are mounted on insulated bases and then
>bonded to the running rails for the same reason.
>

The power supplies are (with rare exceptions) earthed on one pole. The
presence of insulation on the 0v line does not mean that a supply is
not earthed, the most common example being domestic mains supplies (a
"neutral" wire would not be "neutral" if it wasn't earthed at some
point). The absence of an earthed pole is one thing which will
increase the danger of persistent and/or dangerous stray currents due
to the uncertainty of the route that such currents will take. Reasons
for insulating the 0v/neutral conductor include:-
-under fault conditions (e.g. a break close to the power source) a 
 neutral conductor can itself be live - prevention of lethal contact 
 requires either insulation or local bonding to earth
-if it is not separated from surrounding conductive materials it can 
 itself become part of the return path for stray currents

Power supplies running with neither pole earthed are in practice
treated as if all wires are at the maximum available voltage which is
clearly not the case with railway and tramway supplies where for
electrical purposes at least one rail will have little or no effective
insulation from the ground.

LU power supplies (not NR supplies used by LU trains) are a special
case - neither conductor rail is directly earthed but the supply at
the substation is loosely tied to earth via a resistor network and
monitoring circuits are used to detect either pole becoming earthed on
the load side.
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

On 22 Aug 2005 13:34:50 -0700,
billetelic_ferroequinologist@hotmail.com wrote:


>To convert the Southern Region (as was) to 25 kV would be a very
>expensive business as it would be necessary to increase clearances in
>the many cuttings and tunnels that exist by about two to three feet.
>Bear also in mind that many tunnels on the Southern run through chalk,
>not an easy material to tunnel in.


Bearing in mind the clearance at Farringdon, and the possibility of
dropping the floor of tunnels, it ought not to be too difficult.
Changing to double-deck trains is the hard bit.
-- 
Terry Harper
Website Coordinator, The Omnibus Society
http://www.omnibussoc.org

> If the availability of clearances and AC-ready rolling stock coincides
> with future decrepitude of the power supply sytem then it might be
> just another form of ongoing maintenance on some individual lines.



Or, with today's visionless railway an excuse to dieselise completely.

Charles Ellson wrote:

>> >
> The power supplies are (with rare exceptions) earthed on one pole. The
> presence of insulation on the 0v line does not mean that a supply is
> not earthed, the most common example being domestic mains supplies (a
> "neutral" wire would not be "neutral" if it wasn't earthed at some
> point). The absence of an earthed pole is one thing which will
> increase the danger of persistent and/or dangerous stray currents due
> to the uncertainty of the route that such currents will take. Reasons
> for insulating the 0v/neutral conductor include:-
> -under fault conditions (e.g. a break close to the power source) a
>  neutral conductor can itself be live - prevention of lethal contact
>  requires either insulation or local bonding to earth
> -if it is not separated from surrounding conductive materials it can
>  itself become part of the return path for stray currents


Contrary to your assertion, DC traction supplies which use the running
rails for carrying the return current are NOT deliberately earthed and
do indeed float. As the biletelic_ferroequinologist said, the rails are
insulated from earth, the resistance itself may not be very large and
may vary with the soil resistance.

Consider what would happen if you earthed one pole - you would actively
encourage the flow of stray currents towards the earth electrode from
wherever they emanate. Flows of several hundreds of amperes have been
noted when the running rails have been accidentally earthed.

With each site at which the current leaves the rails for a detour via
the earth/utility/cable armour/pipeline/structural reinforcement back
to the earth electrode an anodic region is formed, which strips
electrons from the parent material (usually a metal). Electrons are
deposited back at the earth electrode in a cathodic region (assuming
the neagtive pole is earthed, as it would be in any system with the
rumored exception of the former eastern part of the Berlin S Bahn which
was said to have the positive pole connected to the running rails).

In a perfect electrolyte, for each ampere flowing for one year, it is
possible to liberate 9.14kg of iron. Thus it doesn't take very long
with 100s of amperes flowing to rapidly destroy a utility, structural
reinforcement, pipeline and so on.

By deliberately insulating the running rails and thus one pole from
earth, the stray current flows become much less well defined, diffuse
and variable and the overall stray current burden is reduced.

Ask any utility if they wish a railway undertaking to deliberately
earth one pole of a DC traction system, then take cover.


> Power supplies running with neither pole earthed are in practice
> treated as if all wires are at the maximum available voltage which is
> clearly not the case with railway and tramway supplies where for
> electrical purposes at least one rail will have little or no effective
> insulation from the ground.


In a DC traction system using the running rails to carry the return
current, the running rails float on a resistance to earth that varies
with the prevailing weather conditions. It can be as good as 40kilo
ohms or more, and as bad as a few tens of ohms.

However, because such a system is not deliberately earthed, it is
referenced to the negative pole, or 0V part of the system and earth
references become meaningless in the context of the normal DC current
flows. In practice, the running rails may operate above and below earth
potential by about 60V under normal conditions and in excess of 400V
under short circuit conditions.

Because the insulation to earth can be very good, it is possible to
introduce a hazard when you then introduce earthed metalwork within
touching distance of the running rails. Measures are taken within the
design of the system to either:

A) Prevent direct simultaneous contact by either placing the equipment
out of reach, or by insulating it

Or

B) Limiting the voltage that can be developed between the earthed
metalwork and the negative poles to values in BSEN50123(?) (Control of
accessible and touch voltages)

You will notice at stations that you shouldn't be able to
simultaneously touch the body of a train (at running rail potential)
and a metal lighting standard for instance.


> LU power supplies (not NR supplies used by LU trains) are a special
> case - neither conductor rail is directly earthed but the supply at
> the substation is loosely tied to earth via a resistor network and
> monitoring circuits are used to detect either pole becoming earthed on
> the load side.


Correct.


Richard

On 25 Aug 2005 11:41:50 -0700, RBCatlow@aol.com wrote:


>
>Charles Ellson wrote:
>>> >
>> The power supplies are (with rare exceptions) earthed on one pole. The
>> presence of insulation on the 0v line does not mean that a supply is
>> not earthed, the most common example being domestic mains supplies (a
>> "neutral" wire would not be "neutral" if it wasn't earthed at some
>> point). The absence of an earthed pole is one thing which will
>> increase the danger of persistent and/or dangerous stray currents due
>> to the uncertainty of the route that such currents will take. Reasons
>> for insulating the 0v/neutral conductor include:-
>> -under fault conditions (e.g. a break close to the power source) a
>>  neutral conductor can itself be live - prevention of lethal contact
>>  requires either insulation or local bonding to earth
>> -if it is not separated from surrounding conductive materials it can
>>  itself become part of the return path for stray currents
>
>Contrary to your assertion, DC traction supplies which use the running
>rails for carrying the return current are NOT deliberately earthed and
>do indeed float.


The tone of e.g. RGS GL/RT1254 is that while the return _conductors_
are not to be deliberately earthed there appears to be no prohibition
on the supplies adhering to the standard electrical practice of having
one pole earthed at the origin (AC supplies OTOH appear to involve
deliberate multiple earthing/bonding of the return conductor away from
the supply origin.)


> As the biletelic_ferroequinologist said, the rails are
>insulated from earth, the resistance itself may not be very large and
>may vary with the soil resistance.
>
>Consider what would happen if you earthed one pole - you would actively
>encourage the flow of stray currents towards the earth electrode from
>wherever they emanate.

No you wouldn't. By earthing one side of the supply at source and
keeping that side at as low a resistance as possible between the
source and the load stray currents are minimised as the "proper" route
will tend to short-circuit any undesirable route. Keeping the return
conductor efficiently isolated wherever possible takes away the
opportunity for stray currents to leave (or enter or return) at any
points other than those where the system is designed to cope. While
"earth" should be 0v this isn't true for a nominally "neutral"
conductor.


>Flows of several hundreds of amperes have been
>noted when the running rails have been accidentally earthed.
>

That would suggest that either there's a heck of a lot of stray paths
between there and the substation neutral conductor or that in common
with non-railway practice the return conductor's origin is connected
to earth.

<snip>

>By deliberately insulating the running rails and thus one pole from
>earth, 
>

A steel rail on an iron chair on an often wet sleeper is hardly an
example of "insulating", although some better degree of insulation is
presumably used with modern FB fixings..


>the stray current flows become much less well defined, diffuse
>and variable and the overall stray current burden is reduced.
>

i.e. you don't know where the electrons are going until something
catches fire, breaks or blows up. 

<snip>

>You will notice at stations that you shouldn't be able to
>simultaneously touch the body of a train (at running rail potential)
>and a metal lighting standard for instance.
>

But you can quite easily simultaneously touch the train and metalwork
at the ends of many platforms or where there are e.g. inspection
covers or adjacent footbridges. You can't touch the lamp-posts because
they're placed where they don't get in the way of the passengers.
<snip>

I have deliberately avoided mentioning tramways as these appear to
involve both the possibility of deliberate isolation (to some
practical extent) of the supply from earth (Manchester Metrolink) or
deliberate connection of running rails to earth (HSE Railway safety
principles and guidance - running rails in tram depots) with each
system doing things its own way.
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

Charles Ellson wrote:

> On 25 Aug 2005 11:41:50 -0700, RBCatlow@aol.com wrote:
>
> >
> >Charles Ellson wrote:
>
> The tone of e.g. RGS GL/RT1254 is that while the return _conductors_
> are not to be deliberately earthed there appears to be no prohibition
> on the supplies adhering to the standard electrical practice of having
> one pole earthed at the origin (AC supplies OTOH appear to involve
> deliberate multiple earthing/bonding of the return conductor away from
> the supply origin.)


I can assure you quite categorically that DC Traction supplies Do NOT
have one pole earthed. On AC traction systems, there is quite
deliberate earthing of the return side at the traction transformer and
earthing of the return rail through the footings of each mast.

>

.. By earthing one side of the supply at source and

> keeping that side at as low a resistance as possible between the
> source and the load stray currents are minimised as the "proper" route
> will tend to short-circuit any undesirable route.


Consider a DC traction system whereby the voltage at the rails (casued
by their resistance and the current flowing through them) is 60V above
earth potential at some point along the route. As previously stated,
the rails are lightly insulated from earth.

Case 1: Substation negative NOT earthed. To create a stray current
path, the current has to leak out from the rails and back into the
rails at some point (because the substation negative connection is
heavily insulated from earth) to complete the circuit. Thus the
resistance it has to overcome is effectively two paths in series.

Case 2: Substation negative is earthed. In this case, the current has
to leak out of the rails and then find its way back to the substation
earth electrode. The overall resistance for the stray current path is
lower than for an insulated return.

I think you have to bear in mind that the resistance via the rails from
a distant point on the system is typically 40 or so milliohms, whereas
stray current path resistances may be 1000 times that. So only a small
proportion of current leaves the running rails, compared to that which
returns via the designed path.


>
> >Flows of several hundreds of amperes have been
> >noted when the running rails have been accidentally earthed.
> >
> That would suggest that either there's a heck of a lot of stray paths
> between there and the substation neutral conductor or that in common
> with non-railway practice the return conductor's origin is connected
> to earth.


Yes, potentially many, many stray paths. No, substation negatives are
not deliberately connected to earth.


> >By deliberately insulating the running rails and thus one pole from
> >earth,
> >
> A steel rail on an iron chair on an often wet sleeper is hardly an
> example of "insulating", although some better degree of insulation is
> presumably used with modern FB fixings


Whilst an insulation level of say 1000 ohms is hardly massive in
comparison with what normal electrical practice states is an insulator,
it is some 10,000 times greater than the designed current return path.


>
> >the stray current flows become much less well defined, diffuse
> >and variable and the overall stray current burden is reduced.

> i.e. you don't know where the electrons are going until something
> catches fire, breaks or blows up.


It is true that stray current paths are completey ill defined. The
majority of cases where utilities are affected occur when an accidental
earth is placed on the negative rail of the system and the current
follows that stray current path.


> >You will notice at stations that you shouldn't be able to
> >simultaneously touch the body of a train (at running rail potential)
> >and a metal lighting standard for instance.
> >
> But you can quite easily simultaneously touch the train and metalwork
> at the ends of many platforms or where there are e.g. inspection
> covers or adjacent footbridges. You can't touch the lamp-posts because
> they're placed where they don't get in the way of the passengers.


That doesn't necessarily mean that such items of miscellaneous metal
are deliberately earthed though, for a DC traction system. Placing
beyond reach is a recognised means of preventing direct simultaneous
contact between two systems, as is insulation.


>
> I have deliberately avoided mentioning tramways as these appear to
> involve both the possibility of deliberate isolation (to some
> practical extent) of the supply from earth (Manchester Metrolink) or
> deliberate connection of running rails to earth (HSE Railway safety
> principles and guidance - running rails in tram depots) with each
> system doing things its own way.


I'm glad you mentioned Metrolink, I was closely involved with the
design of the stray current prevention measures for that system. Tram
systems are a much tougher nut to crack from the persepctive of
ensuring that tough potentials are maintained within safe limits, given
the close proximity of other services earthed metalwork and that high
concentrations of utilities that exist within city centres are
protected to some extent from stray currents.

The system adopted for Metrolink and several other tram systems uses
the following principles:

A) Insulate the rails from earth as well as possible - achieved by the
encapsulation of the rails in a polymer - gives better acoustic as well
as electrical insulation.

B) Ensure that the return circuit resistance is as low as possible -
achieved by ensuring good cross bonding and the use of parallel return
conductors.

C) The use of a stray current collection mat of steel mesh placed about
30cm beneath the rails, connected in 300m sections back to a stray
current collector conductor and then connected to the negative
connection of the substation via diodes such that  any stray current
flow into the mesh could be returned in a controlled manner to the
negative. The downside of this has been failure of the diodes after
lightning strikes and so on, earthing the negative by means of the
short circuited diode. A monitoring system has been installed to detect
high, persistent and reverse current flows caused by such faults.

D) Prevention of excessive touch voltages by means of non linear
resistors connected between the negative and earth. Again, stray
current flows increase when these fail short circuit. The original
devices have been replaced by ones with a protechnic disconnector such
that persistent current flows then cause the device to go open circuit.

All of these measures have proven reasonably sucessful, but require a
lot of maintenance. They are not generally employed outside of the city
centre, where the opportunities to affect utilities are considerably
reduced. Item (D) is used wherever there is a danger of excessive touch
voltages.

Such measures are not in widespead use for DC traction systems on main
line railways.


Richard

yyOn 25 Aug 2005 23:25:59 -0700, RBCatlow@aol.com wrote:


>
>Charles Ellson wrote:
>> On 25 Aug 2005 11:41:50 -0700, RBCatlow@aol.com wrote:
>>
>> >
>> >Charles Ellson wrote:
>>
>> The tone of e.g. RGS GL/RT1254 is that while the return _conductors_
>> are not to be deliberately earthed there appears to be no prohibition
>> on the supplies adhering to the standard electrical practice of having
>> one pole earthed at the origin (AC supplies OTOH appear to involve
>> deliberate multiple earthing/bonding of the return conductor away from
>> the supply origin.)
>
>I can assure you quite categorically that DC Traction supplies Do NOT
>have one pole earthed. On AC traction systems, there is quite
>deliberate earthing of the return side at the traction transformer and
>earthing of the return rail through the footings of each mast.
>>

Having gone through GL/RT 1254 (and preceding standards) this looks a
bit like a score draw. My observations are mainly based on the
workings of the DC line which is for nearly all its length either
sharing AC tracks or adjacent to them (the NLL would presumably
involve similar treatment). If the above standard has been adhered to
then one pole will be earthed because it is required to be treated in
the same manner as AC electrified lines due to the proximity/sharing.
The SR can be expected to have settled into a near enough network-wide
standard between grouping and nationalisation and produced the BR
"standard" living on in GL/RT1254 but not all the rest of the
country/world belongs to the SR. LU electrification has already been
gone through on several occasions in this group. Other DC
electrification schemes have existed and still exist in isolation from
the Sarf of England and (barring "standardisation" during more recent
upgrading) there should be no surprise if the designers concerned
produced their own electrical arrangements.
<snip>
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

Charles Ellson wrote:


> Having gone through GL/RT 1254 (and preceding standards) this looks a
> bit like a score draw. My observations are mainly based on the
> workings of the DC line which is for nearly all its length either
> sharing AC tracks or adjacent to them (the NLL would presumably
> involve similar treatment). If the above standard has been adhered to
> then one pole will be earthed because it is required to be treated in
> the same manner as AC electrified lines due to the proximity/sharing.


Why would proximity require the DC return to be bonded to earth?  So
far as sharing (dual electrified sections) is concerned, we have
already had a quite comprehensive explanation of the difficulties
affecting this unusual arrangement, including the difficulty of
accomodating the varying earthing requirements.

On 26 Aug 2005 07:47:25 -0700, "Chippy"  wrote:


>Charles Ellson wrote:
>
>> Having gone through GL/RT 1254 (and preceding standards) this looks a
>> bit like a score draw. My observations are mainly based on the
>> workings of the DC line which is for nearly all its length either
>> sharing AC tracks or adjacent to them (the NLL would presumably
>> involve similar treatment). If the above standard has been adhered to
>> then one pole will be earthed because it is required to be treated in
>> the same manner as AC electrified lines due to the proximity/sharing.
>
>Why would proximity require the DC return to be bonded to earth?  

-To cater for unwanted contact with misbehaving wet string. When the 
 knitting goes "twang" it can spread in all directions. If you have an
 unearthed DC supply which happens to be well isolated from earth at 
 the time (e.g. during a prolonged spell of dry weather) it would
 otherwise be in danger of becoming alive at up 25kV.
-Ditto with wayward OHLE structures some of which can span the whole 
 width of the railway not just AC-equipped tracks.
-Avoiding the dangers caused by a rise in local earth potential 
 arising from events on the AC line which result in the DC return
 rail's voltage difference to local earth exceeding safe limits.

And assorted other reasons which on public supplies are prevented by a
greater degree of insulation than can be achieved with exposed
traction supplies and also by earthing one pole at the supply origin.
<snip>
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

yyOn 26 Aug 2005 11:16:22 -0700, "Chippy"  wrote:


>Charles Ellson wrote:
>
>> -To cater for unwanted contact with misbehaving wet string. When the
>>  knitting goes "twang" it can spread in all directions.
>
>Do you find the English language insufficient for your needs?
>

No, it has enough words and they are there to be used.


>>  If you have an
>>  unearthed DC supply which happens to be well isolated from earth at
>>  the time (e.g. during a prolonged spell of dry weather) it would
>>  otherwise be in danger of becoming alive at up 25kV.
>> -Ditto with wayward OHLE structures some of which can span the whole
>>  width of the railway not just AC-equipped tracks.
>> -Avoiding the dangers caused by a rise in local earth potential
>>  arising from events on the AC line which result in the DC return
>>  rail's voltage difference to local earth exceeding safe limits.
>>
>> And assorted other reasons which on public supplies are prevented by a
>> greater degree of insulation than can be achieved with exposed
>> traction supplies and also by earthing one pole at the supply origin.
>> <snip>
>
>Fine, except that a respected electric traction supply engineer has
>taken the trouble to explain the situation. 

And very detailed and informative it was too and (unless the post
hasn't reached you) I no longer dispute what he explains as the norm.
The way that Metrolink has done it however suggests that the current
method is no longer regarded as good enough (notwithstanding that the
same could be said to apply to DC electrification in general) which
RBC has presumably quoted to show that the industry recognises that.


> Can you point to any
>actual examples that support your assertions?  In the absence of such
>support, I'll stick with the professional view.

Which "assertions" would those be ? If you are referring to my
suggested reasons for why GL/RT1254 effectively requires a
DC-electrified railway common with or adjacent to an AC-electrified
railway to be earthed in the same manner perhaps you can come up with
other reasons. Those which I have suggested would seem to be
reasonably foreseeable mishaps.

 
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

On 26 Aug 2005 12:42:59 -0700, RBCatlow@aol.com wrote:


>Eeeek, this is gitting a mite more complicated.
>

Agreed.
<snip>

>Contrary to Charles' assertions, I am unaware of any DC traction system
>in this country where one pole of the DC supply is deliberaely earthed,
>with the exception of dedicated depot substations at certain (not all)
>light rail depots. In these situations, measures are taken to prevent
>vehicles bridging the block joints and earthing the main line system.
>

Where AC and DC share the same track (e.g. Camden to Euston, sections
of the North London Line and Farringdon station) it's going to be
impossible for the DC supply not to be earthed without some fancy (and
presumably not provided) switching. 

Railway Group Standard GL/RT1254 requires that:-

"4.3 Dual AC / DC electric traction systems
Where AC and DC electric traction systems are either installed on the
same tracks, or installed on different tracks close to one another,
then the requirements of Clause 4.1 shall be met, and additional
control measures shall be taken such that DC stray currents are
restricted to a level as low as reasonably practicable."

The requirements of 4.1 are:
"4.1 AC electric traction systems
4.1.1
AC electric traction systems shall be designed, installed and
maintained to ensure connection of the traction return circuits to the
general mass of earth."

This doesn't contradict your previous explanation WRT to "usual"
arrangements and would seem to be in accord with my understanding that
on the DC and NL lines an earthed supply is used (at least on the
common sections of the latter). There was mention of corrosion
problems (in Railway World?) at the time that the DC line was
converted from 4-rail to 3-rail which would also seem to back up the
arrangements on that line not conforming to what happens elsewhere.
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

Charles Ellson wrote:


> yyOn 26 Aug 2005 11:16:22 -0700, "Chippy"  wrote:
>
> >Charles Ellson wrote:
> >
> >> -To cater for unwanted contact with misbehaving wet string. When the
> >>  knitting goes "twang" it can spread in all directions.
> >
> >Do you find the English language insufficient for your needs?
> >
> No, it has enough words and they are there to be used.


Indeed.  However, sensible people try to use them in a meaningful way.



> And very detailed and informative it was too and (unless the post
> hasn't reached you) I no longer dispute what he explains as the norm.
> The way that Metrolink has done it however suggests that the current
> method is no longer regarded as good enough (notwithstanding that the
> same could be said to apply to DC electrification in general) which
> RBC has presumably quoted to show that the industry recognises that.


He doesn't intimate any such thing.  What he does is give an
explanation of the different method adopted for light rail systems with
street running (note the bit about encapsulating the rails).  As
clearly stated, this need is brought about by the special conditions in
city centres.


>
> > Can you point to any
> >actual examples that support your assertions?  In the absence of such
> >support, I'll stick with the professional view.
> Which "assertions" would those be ? If you are referring to my
> suggested reasons for why GL/RT1254 effectively requires a
> DC-electrified railway common with or adjacent to an AC-electrified
> railway to be earthed in the same manner perhaps you can come up with
> other reasons. Those which I have suggested would seem to be
> reasonably foreseeable mishaps.


You are the one arguing with the expert - you provide the examples.

On 26 Aug 2005 14:43:22 -0700, "Chippy"  wrote:


>Charles Ellson wrote:
>
>> yyOn 26 Aug 2005 11:16:22 -0700, "Chippy"  wrote:
>>
>> >Charles Ellson wrote:
>> >
<snip>
>
>> And very detailed and informative it was too and (unless the post
>> hasn't reached you) I no longer dispute what he explains as the norm.
>> The way that Metrolink has done it however suggests that the current
>> method is no longer regarded as good enough (notwithstanding that the
>> same could be said to apply to DC electrification in general) which
>> RBC has presumably quoted to show that the industry recognises that.
>
>He doesn't intimate any such thing.  What he does is give an
>explanation of the different method adopted for light rail systems with
>street running (note the bit about encapsulating the rails).  As
>clearly stated, this need is brought about by the special conditions in
>city centres.
>

Richard has covered with no little detail both tramway and railway
electrification. It seems as if you are on a slower or less reliable
newsfeed than the rest of us.

>>
>> > Can you point to any
>> >actual examples that support your assertions?  In the absence of such
>> >support, I'll stick with the professional view.
>> Which "assertions" would those be ? If you are referring to my
>> suggested reasons for why GL/RT1254 effectively requires a
>> DC-electrified railway common with or adjacent to an AC-electrified
>> railway to be earthed in the same manner perhaps you can come up with
>> other reasons. Those which I have suggested would seem to be
>> reasonably foreseeable mishaps.
>
>You are the one arguing with the expert - you provide the examples.


I'm not arguing with the expert. I have taken heed of his advice and
followed up by reading other information (which I have identified in
other posts) and which WRT the general provision of DC electrification
on railways reinforces what he has said. There are however exceptions
to many rules (in this case the Euston-Watford DC line which in
various ways has always been "non-conformist") which do not disprove
the general rules but which for some reason you have chosen to
interpret as me totally contradicting the advice from someone rather
closer to the subject under discussion.
As for examples, those which I suggested are easily foreseeable events
which which would be made more harmless by taking the measures in the
document referred to. Perhaps you can enlighten us with why you think
the events I suggested have no relevance to varying the standard
methods of bonding and earthing (where used) on DC electrified lines
where high voltage lines are in the vicinity ? 
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|

Charles Ellson wrote:


> On 26 Aug 2005 14:43:22 -0700, "Chippy"  wrote:

> >He doesn't intimate any such thing.  What he does is give an
> >explanation of the different method adopted for light rail systems with
> >street running (note the bit about encapsulating the rails).  As
> >clearly stated, this need is brought about by the special conditions in
> >city centres.
> >
> Richard has covered with no little detail both tramway and railway
> electrification. It seems as if you are on a slower or less reliable
> newsfeed than the rest of us.


You are not making sense.  I have obviously seen the posting in order
to comment upon the fact that it doesn't intimate what you suggested
that it did.

Please refrain from further foolishness.

On 22 Aug 2005 13:34:50 -0700 someone who may be
billetelic_ferroequinologist@hotmail.com wrote this:-


>So, all in all, a non-starter.


Converting the "Southern Region" to 25kV may not be the best use of
money, but it is certainly feasible.


-- 
 David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
 I will always explain revoked keys, unless the UK government
 prevents me by using the RIP Act 2000.

yyOn Tue, 23 Aug 2005 06:58:43 +0100, David Hansen
 wrote:


>On 22 Aug 2005 13:34:50 -0700 someone who may be
>billetelic_ferroequinologist@hotmail.com wrote this:-
>
>>So, all in all, a non-starter.
>
>Converting the "Southern Region" to 25kV may not be the best use of
>money, but it is certainly feasible.


If the availability of clearances and AC-ready rolling stock coincides
with future decrepitude of the power supply sytem then it might be
just another form of ongoing maintenance on some individual lines.
-- 
                                                             _______
 +---------------------------------------------------+      |\\   //|
 | Charles Ellson: charles@e11son.demon.co.uk        |      | \\ // |
 +---------------------------------------------------+      |  > <  |
                                                            | // \\ |
                                              Alba gu brath |//___\\|