My trains (FCC) were totally FUBAR last night thanks to the overhead
power lines coming down.

It does seem to be a piss poor way to power a railway, this is always
happening, especially in winter when it gets a bit windy.

How many fatalities are there each year on parts of the network
powered by live rails as opposed to OHLs?

Rgds
Ed

On Wed, 2 Jul 2008 03:18:00 -0700 (PDT) someone who may be Ed the
Amateur  wrote this:-

>How many fatalities are there each year on parts of the network
>powered by live rails as opposed to OHLs?

Enough that new installations with unprotected conductor rails are
not permitted (and have not been permitted for a long time), other
than extensions to existing systems.

Even without that restriction, practical conductor rail systems are
not able to deliver sufficient power to drive fast trains. The power
transmitted could be raised by raising the voltage, but this runs
into the practicality of providing sufficient insulation around the
(protected) conductor rail in what is a small space full of
contaminants. Unprotected conductor rails at say 3000V would not be
looked on with favour by most people.

Unless someone wants the expense of dual collection arrangements on
high speed trains, one system of electrification is sensible and
that will be an overhead system. If conductor rail systems could be
swept away with a snap of the fingers that would be even better, but
that is not practical.



-- 
  David Hansen, Edinburgh 
 I will *always* explain revoked encryption keys, unless RIP prevents me
 http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Hi,
Yes if one looks at the power requirements for a class 91 being 6300bhp 
which comes out at 4.7MW, which at 25kV comes out at abouth 188A.

Now for the same power at 750V you would have to draw currents like 6266A.

Now even when using twelve (or even eighteen plus, using poly-thingy 
transformers) pulse rectification which I believe they do to reduce 
harmonics on the (supply) system, you would have to have multiple 
current collection shoes.

I don't like third rail anyway, it's scraggy way of collecting energy
in my view.

Much better to have properly strung knitting, which the ECML has never 
had, because it was done on the cheap by BR with no gov money.

Cheers,

Rob.

David Hansen wrote:
> On Wed, 2 Jul 2008 03:18:00 -0700 (PDT) someone who may be Ed the
> Amateur  wrote this:-
> 
>> How many fatalities are there each year on parts of the network
>> powered by live rails as opposed to OHLs?
> 
> Enough that new installations with unprotected conductor rails are
> not permitted (and have not been permitted for a long time), other
> than extensions to existing systems.
> 
> Even without that restriction, practical conductor rail systems are
> not able to deliver sufficient power to drive fast trains. The power
> transmitted could be raised by raising the voltage, but this runs
> into the practicality of providing sufficient insulation around the
> (protected) conductor rail in what is a small space full of
> contaminants. Unprotected conductor rails at say 3000V would not be
> looked on with favour by most people.
> 
> Unless someone wants the expense of dual collection arrangements on
> high speed trains, one system of electrification is sensible and
> that will be an overhead system. If conductor rail systems could be
> swept away with a snap of the fingers that would be even better, but
> that is not practical.
> 
> 
>

David Hansen wrote:
> Enough that new installations with unprotected conductor rails are
> not permitted (and have not been permitted for a long time), other
> than extensions to existing systems.

Surely though you could "extend" a current system and do the entire 
network with it?

For example (and please no one take this as a serious suggestion) extend 
the electrification from the North London Line at Stratford to high 
level, you could then "extend" that to Norwich, Kings Lynn, Peterborough 
York etc and all lines connected.

Or are there limits on extension lengths?

"Great Eastern"  wrote in message 
news:486b6ab7$0$26087$db0fefd9@news.zen.co.uk...
> David Hansen wrote:
>> Enough that new installations with unprotected conductor rails are
>> not permitted (and have not been permitted for a long time), other
>> than extensions to existing systems.
>
> Surely though you could "extend" a current system and do the entire 
> network with it?
>
> For example (and please no one take this as a serious suggestion) extend 
> the electrification from the North London Line at Stratford to high level, 
> you could then "extend" that to Norwich, Kings Lynn, Peterborough York etc 
> and all lines connected.
>
> Or are there limits on extension lengths?

Network rail's plans apparently include Basingstoke, Eastleigh and Redbridge 
to Salisbury - that's a fairly decent mileage...

Paul

Paul Scott wrote:
> "Great Eastern"  wrote in message 
> news:486b6ab7$0$26087$db0fefd9@news.zen.co.uk...
>> David Hansen wrote:
>>> Enough that new installations with unprotected conductor rails are
>>> not permitted (and have not been permitted for a long time), other
>>> than extensions to existing systems.
>> Surely though you could "extend" a current system and do the entire 
>> network with it?
>>
>> For example (and please no one take this as a serious suggestion) extend 
>> the electrification from the North London Line at Stratford to high level, 
>> you could then "extend" that to Norwich, Kings Lynn, Peterborough York etc 
>> and all lines connected.
>>
>> Or are there limits on extension lengths?
> 
> Network rail's plans apparently include Basingstoke, Eastleigh and Redbridge 
> to Salisbury - that's a fairly decent mileage...
> 
> Paul 
> 
> 
Yes but I think that no new 'isolated' runs of third rail are allowed by 
HMRI.

You can extend as far as you like, which is why the Watercress Line were 
talking about putting in third rail at one time.  Does anyone know if 
this is still an intention?

Rob.

"David Hansen"  wrote
>
> Unless someone wants the expense of dual collection arrangements on
> high speed trains, one system of electrification is sensible and
> that will be an overhead system. If conductor rail systems could be
> swept away with a snap of the fingers that would be even better, but
> that is not practical.
>
At one extreme, LUL won't be going over to 25kV AC OHLE anytime this
century, nor will most of the ex-SR third rail territory, and extensions of
these are likely to utilise existing systems.

But the cost of substations, and the lineside fencing which is now required
for new third rail installations makes it much more expensive than OHLE. It
seemed obvious that, if Bidston - Wrexham was to be electrified it would be
third rail. It now seems that better value would be obtained by using 25kV
OHLE, and timing it for the time when the existing Merseyrail stock has to
be replaced. Through running to Liverpool via the Mersey tunnel would then
be possible, with voltage changeover at Bidston.

Peter

Peter Masson wrote:
> "David Hansen"  wrote
>> Unless someone wants the expense of dual collection arrangements on
>> high speed trains, one system of electrification is sensible and
>> that will be an overhead system. If conductor rail systems could be
>> swept away with a snap of the fingers that would be even better, but
>> that is not practical.
>>
> At one extreme, LUL won't be going over to 25kV AC OHLE anytime this
> century, nor will most of the ex-SR third rail territory, and extensions of
> these are likely to utilise existing systems.
> 
> But the cost of substations, and the lineside fencing which is now required
> for new third rail installations makes it much more expensive than OHLE. It
> seemed obvious that, if Bidston - Wrexham was to be electrified it would be
> third rail. It now seems that better value would be obtained by using 25kV
> OHLE, and timing it for the time when the existing Merseyrail stock has to
> be replaced. Through running to Liverpool via the Mersey tunnel would then
> be possible, with voltage changeover at Bidston.
> 
> Peter
> 
> 
Yes that sounds feasible because the costs of a third rail energy 
delivery system would be far higher than for a 25kV overhead AC system. 
  You have to have much more complicated transformers with dual 
seconadry windings to give you your 60 degree phase shift and then you 
have your converter rectifiers.

Even with the cost of the support steel work for OHLE it would still be 
a lot cheaper.  Much less copper involved because of the lower current, 
and single phase too.


Rob.

"Peter Masson"  wrote in message 
news:GIGdnZ97t8s76_bVnZ2dnUVZ8radnZ2d@bt.com...
>

> But the cost of substations, and the lineside fencing which is now 
> required
> for new third rail installations makes it much more expensive than OHLE. 
> It
> seemed obvious that, if Bidston - Wrexham was to be electrified it would 
> be
> third rail. It now seems that better value would be obtained by using 25kV
> OHLE, and timing it for the time when the existing Merseyrail stock has to
> be replaced. Through running to Liverpool via the Mersey tunnel would then
> be possible, with voltage changeover at Bidston.
>

Would they also be able to fit something like an ex-Thameslink 319 through 
the loop? They could be spruced up in the same way as the 507/8s were...

Paul

Robert Wilson wrote:
> Hi,
> Yes if one looks at the power requirements for a class 91 being 6300bhp 
> which comes out at 4.7MW, which at 25kV comes out at abouth 188A.
> 
> Now for the same power at 750V you would have to draw currents like 6266A.

The Eurostar sets managed 3.4 MW on 3rd rail, which is probably about 
the limit of that method.

> Now even when using twelve (or even eighteen plus, using poly-thingy 
> transformers) pulse rectification which I believe they do to reduce 
> harmonics on the (supply) system, you would have to have multiple 
> current collection shoes.

I'm not sure what the presence of harmonics in the supply has to do with 
the number of shoes.  The number of shoes required will be dependent on 
the current capacity of each shoe and the need to reduce the risk of a 
train getting gapped.  The first issue applies equally to overhead 
lines, particularly on 1500V systems where the current capacity of a 
single pan is often not enough to supply the power requirement.  Staying 
with the Eurostar example, for 1.7 MW per power car, they didn't need an 
excessive number of shoes.

> I don't like third rail anyway, it's scraggy way of collecting energy
> in my view.

But then when was the last time you heard of train service being 
disrupted because of 3rd rail issues?  It is a good system for certain 
purposes, such as metros where speeds are low and trains are frequent. 
It was foolish of the Southern to have persisted with it beyond London 
suburban areas, but if anything can be said of the system, it is reliable.

> Much better to have properly strung knitting, which the ECML has never 
> had, because it was done on the cheap by BR with no gov money.

Though the wires seem to keep coming down at places like Welwyn and 
Stevenage, which were wired in the '70s, presumably to the same spec as 
the northern part of the WCML, rather than the Peterborough - 
Leeds/Edinburgh stretch done on the cheap in the '80s.  This seems to me 
to be a problem of poor maintenance of trains and catenery rather than 
an initial design problem.  After all, how often is the WCML delayed by 
wires being pulled down in Carlisle?

Robin

Robert Wilson wrote:
> Peter Masson wrote:
>> "David Hansen"  wrote
>>> Unless someone wants the expense of dual collection arrangements on
>>> high speed trains, one system of electrification is sensible and
>>> that will be an overhead system. If conductor rail systems could be
>>> swept away with a snap of the fingers that would be even better, but
>>> that is not practical.
>>>
>> At one extreme, LUL won't be going over to 25kV AC OHLE anytime this
>> century, nor will most of the ex-SR third rail territory, and 
>> extensions of
>> these are likely to utilise existing systems.
>>
>> But the cost of substations, and the lineside fencing which is now 
>> required
>> for new third rail installations makes it much more expensive than 
>> OHLE. It
>> seemed obvious that, if Bidston - Wrexham was to be electrified it 
>> would be
>> third rail. It now seems that better value would be obtained by using 
>> 25kV
>> OHLE, and timing it for the time when the existing Merseyrail stock 
>> has to
>> be replaced. Through running to Liverpool via the Mersey tunnel would 
>> then
>> be possible, with voltage changeover at Bidston.
>>
>> Peter
>>
>>
> Yes that sounds feasible because the costs of a third rail energy 
> delivery system would be far higher than for a 25kV overhead AC system. 
>  You have to have much more complicated transformers with dual seconadry 
> windings to give you your 60 degree phase shift and then you have your 
> converter rectifiers.
> 
> Even with the cost of the support steel work for OHLE it would still be 
> a lot cheaper.  Much less copper involved because of the lower current, 
> and single phase too.

Though the fact that ac electrification is single phase can cause 
trouble with balancing the load across the three phases, as an express 
train is a very large unbalanced load.  On dc systems, the substation 
load is balanced across all three phases.

Robin

On 2 Jul., 15:28, "R.C. Payne"  wrote:

> Though the fact that ac electrification is single phase can cause
> trouble with balancing the load across the three phases, as an express
> train is a very large unbalanced load.  On dc systems, the substation
> load is balanced across all three phases.

That is, if the railway is fed from a single phase. Of course if you
use a rotary converter or the static-state equivalent then you load
all three phases equally. This is done for example on 16.7Hz systems
such as in Germany and Switzerland, but could theoretically also be
done for 50Hz systems.

On Wed, 02 Jul 2008 12:48:37 +0100 someone who may be Great Eastern
 wrote this:-

>David Hansen wrote:
>> Enough that new installations with unprotected conductor rails are
>> not permitted (and have not been permitted for a long time), other
>> than extensions to existing systems.
>
>Surely though you could "extend" a current system and do the entire 
>network with it? [snip]
>
>Or are there limits on extension lengths?

I suspect that there are none written down, BICBW.

However, I think that the Railway Inspectorate would have something
to say about the reasonableness of extending conductor rails from
say Watford Junction to Liverpool South Parkway. I imagine the
phrase, "taking the piss", would feature prominently in private.

Safety is a subject which revolves around what is reasonable and
practical.



-- 
  David Hansen, Edinburgh 
 I will *always* explain revoked encryption keys, unless RIP prevents me
 http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"Paul Scott"  wrote:
>
>Network rail's plans apparently include Basingstoke, Eastleigh and Redbridge 
>to Salisbury - that's a fairly decent mileage...


It would make sense, though.  However, what happens when you get to
Salisbury and start thinking about Exeter?  

It has long been stated that the Exeter main line could not be
electrified on the third rail system, I think because of drainage
problems?  Perhaps someone could confirm.

I suppose that dual voltage stock could be used to enable 25kV OHLE to
be installed west of Salisbury.

"Paul Scott"  wrote:

>
>"Peter Masson"  wrote in message 
>news:GIGdnZ97t8s76_bVnZ2dnUVZ8radnZ2d@bt.com...
>>
>
>> But the cost of substations, and the lineside fencing which is now 
>> required
>> for new third rail installations makes it much more expensive than OHLE. 
>> It
>> seemed obvious that, if Bidston - Wrexham was to be electrified it would 
>> be
>> third rail. It now seems that better value would be obtained by using 25kV
>> OHLE, and timing it for the time when the existing Merseyrail stock has to
>> be replaced. Through running to Liverpool via the Mersey tunnel would then
>> be possible, with voltage changeover at Bidston.
>>
>
>Would they also be able to fit something like an ex-Thameslink 319 through 
>the loop? They could be spruced up in the same way as the 507/8s were...


Originally the Loop tunnel was due to be lined with sprayed concrete.
However, after unsuccessful trials, it was decided to provide a much
thicker in-situ concrete lining.   The setting out of the lining was
problematic, even on curves, and the designers of the track alignment
through the as-built tunnel had quite a lot of difficulty making the
trains fit.

I don't think a 319 (or possibly any of the Mk3 based EMU stock) would
fit through the Loop.  The Mk3 design sticks further out at cantrail
level than the 507/508 design, which is PEP-based and is narrower and
lower at this point.  Clearance is at a premium in some places along
the Loop tunnel, even for that stock.

"R.C. Payne"  wrote:
>
>But then when was the last time you heard of train service being 
>disrupted because of 3rd rail issues?


My train service (on the Brighton Line) was disrupted on about 10-12
different occasions as a direct result of conductor rail problems in
the space of five and a half years.  I don't know how that compares
with the reliability of 25kV OHLE but it doesn't seem particularly
good to me.

On 2 Jul, 14:25, "R.C. Payne"  wrote:
> > I don't like third rail anyway, it's scraggy way of collecting energy
> > in my view.
>
> But then when was the last time you heard of train service being
> disrupted because of 3rd rail issues?

Happens on the Southern and on LUL most winters - 3rd rails don't like
freezing. EMU breakdowns caused by broken shoes aren't unknown,
either.

> It is a good system for certain
> purposes, such as metros where speeds are low and trains are frequent.

Broadly agree, although if you were starting afresh today then
something more like the DLR's protected contact rail would be good.

> It was foolish of the Southern to have persisted with it beyond London
> suburban areas, but if anything can be said of the system, it is reliable.

Again, reliable-ish once you've made the enormous capital investment
in transformers. In the Southern's defence, it's quite hard to know
where you'd draw the line (eg on the SWML you've got a 4-track railway
from Wimbledon to Brookwood with trains that run on the slows from
Wimbledon all the way to Guildford, Basingstoke and Alton - you've not
got the nice self-contained suburban vs urban boundary of the DC lines
or the NLR...)

> > Much better to have properly strung knitting, which the ECML has never
> > had, because it was done on the cheap by BR with no gov money.
>
> Though the wires seem to keep coming down at places like Welwyn and
> Stevenage, which were wired in the '70s, presumably to the same spec as
> the northern part of the WCML, rather than the Peterborough -
> Leeds/Edinburgh stretch done on the cheap in the '80s.  This seems to me
> to be a problem of poor maintenance of trains and catenery rather than
> an initial design problem.  After all, how often is the WCML delayed by
> wires being pulled down in Carlisle?

Not sure what the literal answer is - but it'd be interesting to see
actual delay minutes attributable to wires-coming-down. My suspicion
is that the obvious visibility of de-wirings compared with other track/
signalling/train incidents means they're massively overstated as a
cause of delay...

--
John Band
john at johnband dot org
www.johnband.org

In message <486b6ab7$0$26087$db0fefd9@news.zen.co.uk>
          Great Eastern  wrote:

> David Hansen wrote:
>> Enough that new installations with unprotected conductor rails are
>> not permitted (and have not been permitted for a long time), other
>> than extensions to existing systems.

> Surely though you could "extend" a current system and do the entire
> network with it?

> For example (and please no one take this as a serious suggestion) extend
> the electrification from the North London Line at Stratford to high
> level, you could then "extend" that to Norwich, Kings Lynn, Peterborough
> York etc and all lines connected.

> Or are there limits on extension lengths?

Well, there is talk of extending the MerseyRail system from Bidston to 
Wrexham, but the extension would 25KV OH. And any of these would be 
also.

Michael Bell

--

On Jul 2, 3:04 pm, Tony Polson  wrote:

> It would make sense, though.  However, what happens when you get to
> Salisbury and start thinking about Exeter?

> I suppose that dual voltage stock could be used to enable 25kV OHLE to
> be installed west of Salisbury.

If west of Worting Jn were considered as a single scheme, or to
Salisbury with an optional future extension, all at one go, then it
would be logical to have it all as 25 kV. Only if Salisbury were dealt
with seperately under a ''no plans'' for Exeter scheme would third
rail make sense.

One other factor these days to take into account is that existing
rolling stock of current generation (excuse the pun) with AC motors is
in effect already dual traction fitted or easily capable of
conversion. This would impact on the economics of extending the
Southern Electric zone by 25 kV.


--
Nick

"Tony Polson"  wrote
>
> It has long been stated that the Exeter main line could not be
> electrified on the third rail system, I think because of drainage
> problems?  Perhaps someone could confirm.
>
> I suppose that dual voltage stock could be used to enable 25kV OHLE to
> be installed west of Salisbury.
>
I don't think that there has ever been a serious investigation into the
possibility of electrifying the SR route through to Exeter. AIUI the SR
would have liked to follow up the Bournemouth electrification with adding
juice rails to Basingstoke (Worting Junction) to Salisbury, and would have
operated it in the same way as they did the Weymouth line when the 3rd rail
ran as far as Bournemouth, i.e. REP+TC to Salisbury, with a 33 taking the TC
on to Exeter push-pull.

The decision to downgrade and single the SR Exeter line had been taken
before the decision to electrify to Exeter. In the parallel universe in
which this became the trunk line to the west we might have ended up with
OHLE from Woking/Brookwood to Bournemouth (Weymouth) and Exeter, with dual
voltage REPs running as far as Exeter, switching between 3rd rail and OHLE
between Woking and Brookwood, and with 33s taking on TCs beyond Exeter to
both GW and SR destinations.

On Jul 2, 3:39 pm, Tony Polson  wrote:

> I don't think a 319 (or possibly any of the Mk3 based EMU stock) would
> fit through the Loop.

I concur: AIUI this particluar line is restricted to type 507/508/313
body profile only.


Things may change of course: 508s when on the SR first time around
were absolutely forbidden into CX/CS/BF terminals due to clearances
(not that they ever need to work to those places) but the second time
around with SET 508s work without such limits - presumably due to
ongoing creeping infrastructure changes to do with 319 455 465 375 etc
work. Especially important here was 455/319 which as you rightly say
is wider on some dimensions - so fitting those as a more restirctive
type permitted 508 by default.

I can't imagine though what creeping changes might have taken place on
the Liverpool loop though.

--
Nick

"Robert Wilson"  wrote in message 
news:sfadnSMLEMMp-vbVnZ2dnUVZ8vKdnZ2d@posted.plusnet...
> Hi,
> Yes if one looks at the power requirements for a class 91 being 6300bhp 
> which comes out at 4.7MW, which at 25kV comes out at abouth 188A.
>
> Now for the same power at 750V you would have to draw currents like 6266A.
>
> Now even when using twelve (or even eighteen plus, using poly-thingy 
> transformers) pulse rectification which I believe they do to reduce 
> harmonics on the (supply) system, you would have to have multiple current 
> collection shoes.
>
> I don't like third rail anyway, it's scraggy way of collecting energy
> in my view.
>
> Much better to have properly strung knitting, which the ECML has never 
> had, because it was done on the cheap by BR with no gov money.

From the aesthetic point of view, third rail definitely wins hands down: 
OHLE, gantries, knitting etc looks very unsightly.

But from all other points of view, OHLE is superior.

Both systems can be affected by the weather: the third rail can get coated 
in an insulating layer of ice whereas the OHLE line can be brought down by 
high winds or a faulty pantograph.

On 2 Jul, 12:47, "Mortimer"  wrote:
> "Robert Wilson"  wrote in message
>
> news:sfadnSMLEMMp-vbVnZ2dnUVZ8vKdnZ2d@posted.plusnet...
>
>
>
> > Hi,
> > Yes if one looks at the power requirements for a class 91 being 6300bhp
> > which comes out at 4.7MW, which at 25kV comes out at abouth 188A.
>
> > Now for the same power at 750V you would have to draw currents like 6266A.
>
> > Now even when using twelve (or even eighteen plus, using poly-thingy
> > transformers) pulse rectification which I believe they do to reduce
> > harmonics on the (supply) system, you would have to have multiple current
> > collection shoes.
>
> > I don't like third rail anyway, it's scraggy way of collecting energy
> > in my view.
>
> > Much better to have properly strung knitting, which the ECML has never
> > had, because it was done on the cheap by BR with no gov money.
>
> From the aesthetic point of view, third rail definitely wins hands down:
> OHLE, gantries, knitting etc looks very unsightly.

Eye of the beholder and all that - I rather like the look of a new
electrified mainline like HS1, and it can work even on heritage
structures:
http://www.cintec.com/en/applications/Archtec/documents/royal_border.htm

[which was apparently electrified "for high-speed InterCity 125
trains", presumably to deter people from riding on the roof]

--
John Band
john at johnband dot org
www.johnband.org

"Tony Polson"  wrote
>
> I don't think a 319 (or possibly any of the Mk3 based EMU stock) would
> fit through the Loop.  The Mk3 design sticks further out at cantrail
> level than the 507/508 design, which is PEP-based and is narrower and
> lower at this point.  Clearance is at a premium in some places along
> the Loop tunnel, even for that stock.
>
But the eventual replacements for the 507/508 stock will undoubtedly be
purpose-built to fit the tunnels, and will be dual-voltage if Merseytravel's
aspirations to electrify Bidston - Wrexham, Hunts Cross - Warrington,
Kirkby - Wigan, and Ormskirk - Southport/Preston are to be achieved.

Peter

David Hansen wrote:

> On Wed, 2 Jul 2008 03:18:00 -0700 (PDT) someone who may be Ed the
> Amateur  wrote this:-
> 
>>How many fatalities are there each year on parts of the network
>>powered by live rails as opposed to OHLs?
> 
> Enough that new installations with unprotected conductor rails are
> not permitted (and have not been permitted for a long time), other
> than extensions to existing systems.

Really? One doesn't hear of many. Last Friday at Clapham Junction, I was
watching an orange-jacketed worker as he made his way across the tracks.
At one point, when he was only about five metres away from me, I would
swear that the back of his trousers brushed against a conductor rail as
he stepped over it. Nothing happened.

-- 
http://gallery120232.fotopic.net/p13309774.html
(50 003 at London Paddington, 29 Nov 1980)

On Wed, 2 Jul 2008 16:32:45 +0100 someone who may be "Peter Masson"
 wrote this:-

>REP+TC to Salisbury, with a 33 taking the TC
>on to Exeter push-pull.

Given that the Western Region generally provided the locomotives for
this service, other than the period when 33s operated it, I suspect
they would not have been keen. Presumably the WR and SR agreed on
this arrangement some time before the abolition of steam on the
route, after some of the line had been transferred to the WR.

Class 42/43 locomotives fitted with SR style MU pipes/cables would
have a certain place in the league table of ugliness. IIRC one was
fitted with at least some ETH components, but it was not considered
worthwhile to convert the class.

>The decision to downgrade and single the SR Exeter line had been taken
>before the decision to electrify to Exeter. In the parallel universe in
>which this became the trunk line to the west we might have ended up with
>OHLE from Woking/Brookwood to Bournemouth (Weymouth) and Exeter, with dual
>voltage REPs running as far as Exeter, switching between 3rd rail and OHLE
>between Woking and Brookwood, and with 33s taking on TCs beyond Exeter to
>both GW and SR destinations.

Consideration was given to making the REPs dual voltage. However,
this was in the context of using a protected conductor rail
energised at IIRC 1500V DC once outside London and its environs
(possibly from Woking/Brookwood). The problems of two sets of
shoegear, including keeping the "other sort" of shoegear off the
conductor rail would certainly have been challenging.



-- 
  David Hansen, Edinburgh 
 I will *always* explain revoked encryption keys, unless RIP prevents me
 http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

amogles@yahoo.com wrote:
> On 2 Jul., 15:28, "R.C. Payne"  wrote:
> 
>> Though the fact that ac electrification is single phase can cause
>> trouble with balancing the load across the three phases, as an express
>> train is a very large unbalanced load.  On dc systems, the substation
>> load is balanced across all three phases.
> 
> That is, if the railway is fed from a single phase. Of course if you
> use a rotary converter or the static-state equivalent then you load
> all three phases equally. This is done for example on 16.7Hz systems
> such as in Germany and Switzerland, but could theoretically also be
> done for 50Hz systems.
There was an earlier discussion about load balancing on OHLE systems and 
is appears that mostly they distribute over different supply phases like 
domestic final distribution at street level.  Ie, every third house 
being on the red phase etc.

Rob.

D7666  wrote:

>On Jul 2, 3:04 pm, Tony Polson  wrote:
>
>> It would make sense, though.  However, what happens when you get to
>> Salisbury and start thinking about Exeter?
>
>> I suppose that dual voltage stock could be used to enable 25kV OHLE to
>> be installed west of Salisbury.
>
>If west of Worting Jn were considered as a single scheme, or to
>Salisbury with an optional future extension, all at one go, then it
>would be logical to have it all as 25 kV. Only if Salisbury were dealt
>with seperately under a ''no plans'' for Exeter scheme would third
>rail make sense.


Of course.  But I think that, in the real world, electrifying to
Exeter would only be considered after electrification to Salisbury had
already been completed.


>One other factor these days to take into account is that existing
>rolling stock of current generation (excuse the pun) with AC motors is
>in effect already dual traction fitted or easily capable of
>conversion. This would impact on the economics of extending the
>Southern Electric zone by 25 kV.


Indeed.  Does the conversion from DC to variable frequency AC consume
a significant amount of power?

Chris Tolley wrote:
> David Hansen wrote:
> 
>> On Wed, 2 Jul 2008 03:18:00 -0700 (PDT) someone who may be Ed the
>> Amateur  wrote this:-
>>
>>> How many fatalities are there each year on parts of the network
>>> powered by live rails as opposed to OHLs?
>> Enough that new installations with unprotected conductor rails are
>> not permitted (and have not been permitted for a long time), other
>> than extensions to existing systems.
> 
> Really? One doesn't hear of many. Last Friday at Clapham Junction, I was
> watching an orange-jacketed worker as he made his way across the tracks.
> At one point, when he was only about five metres away from me, I would
> swear that the back of his trousers brushed against a conductor rail as
> he stepped over it. Nothing happened.
> 
If he'd got damp trousers then you would have seen some fireworks. 
Depends on how high an impedance his boots are too.

If he completes a circuit then you and he would know about it. 
Doubtless so would the rest of us on the news that night.

Rob.

"Peter Masson"  wrote:
>
>I don't think that there has ever been a serious investigation into the
>possibility of electrifying the SR route through to Exeter. AIUI the SR
>would have liked to follow up the Bournemouth electrification with adding
>juice rails to Basingstoke (Worting Junction) to Salisbury, and would have
>operated it in the same way as they did the Weymouth line when the 3rd rail
>ran as far as Bournemouth, i.e. REP+TC to Salisbury, with a 33 taking the TC
>on to Exeter push-pull.
>
>The decision to downgrade and single the SR Exeter line had been taken
>before the decision to electrify to Exeter. In the parallel universe in
>which this became the trunk line to the west we might have ended up with
>OHLE from Woking/Brookwood to Bournemouth (Weymouth) and Exeter, with dual
>voltage REPs running as far as Exeter, switching between 3rd rail and OHLE
>between Woking and Brookwood, and with 33s taking on TCs beyond Exeter to
>both GW and SR destinations.


There was definitely a study done by BR, possibly in Network SouthEast
days but more likely before that.  I recall reading about it in a
magazine, probably Modern Railways (but I'm not sure), and statements
were made about the impracticability of using third rail because of
not-infrequent flooding of the permanent way.  For that reason, 25kV
OHLE would have been preferred. 

The reason I think it was in pre-NSE days is that the Class 319 units
for Thameslink forever changed the perception of routes with dual
third rail and 25kV OHLE electrification.  I know that the Class 313
EMUs had this feature before, but I had the impression that a
widespread acceptance that routinely changing over between systems was
viable did not arrive until the 319s had proved themselves.

"Peter Masson"  wrote:
>"Tony Polson"  wrote
>>
>> I don't think a 319 (or possibly any of the Mk3 based EMU stock) would
>> fit through the Loop.  The Mk3 design sticks further out at cantrail
>> level than the 507/508 design, which is PEP-based and is narrower and
>> lower at this point.  Clearance is at a premium in some places along
>> the Loop tunnel, even for that stock.
>>
>But the eventual replacements for the 507/508 stock will undoubtedly be
>purpose-built to fit the tunnels, and will be dual-voltage if Merseytravel's
>aspirations to electrify Bidston - Wrexham, Hunts Cross - Warrington,
>Kirkby - Wigan, and Ormskirk - Southport/Preston are to be achieved.


Yes, of course you're right, Peter, but I was replying specifically to
Paul Scott's point about the possibility of using refurbished
ex-Thameslink Class 319 units on the Loop.   

Aside from the gauge problem, it would otherwise be an excellent idea.

In message <g4fvkk$4iv$1@gemini.csx.cam.ac.uk>
          "R.C. Payne"  wrote:

[snip]
> 
> But then when was the last time you heard of train service being 
> disrupted because of 3rd rail issues?  

In cold and snowy weather you can get severe arcing that can damage the
collector shoes leaving a train stranded.

-- 
Graeme Wall
This address is not read, substitute trains for rail.
Transport Miscellany at <http://www.greywall.demon.co.uk/rail/index.html>

On Wed, 02 Jul 2008 17:05:21, David Hansen
 wrote:
>
>Class 42/43 locomotives fitted with SR style MU pipes/cables would
>have a certain place in the league table of ugliness. IIRC one was
>fitted with at least some ETH components, but it was not considered
>worthwhile to convert the class.

D870 Zulu

Paul Harley

"Graeme Wall"  wrote
>
> In cold and snowy weather you can get severe arcing that can damage the
> collector shoes leaving a train stranded.
>
It has been known for the arcing to weld the shoes to the conductor rail.
When this happens on Sole Street bank it can end up with 5 hour delays.

Peter

Methinks there are a number of comments out of step with the time line
of the real world.

> >The decision to downgrade and single the SR Exeter line had been taken
> >before the decision to electrify to Exeter.

What decision to electrify to Exeter before singling ?

There was no such decision. There was a ''wish list'' plan to
electrify all SR routes east of an arbitrary line drawn through
Salisbury and Bournemouth, thats all.

> Consideration was given to making the REPs dual voltage.

Proof ???

I'll put money on you will not find this anywhere except in uninformed
fantasy ramblings.

The only alternative phase in Rep genesis was four car tractor units
with all four coaches motored by 16 EE507 motors.

The reason was quite simple - there was no dual voltage Rep plan
because 25 kV ideas were abandoned way way before they embarked on
push-pull of the route. Likewise all higher voltage DC ideas had been
dropped first too.

They may well have been devising a dual voltage AC/DC or two-system DC
EMU. But it was an EMU not a tractor. Tractoring the line came quite
late.

--
Nick

On Jul 2, 5:29 pm, Tony Polson  wrote:
> "Peter Masson"  wrote:
> >"Tony Polson"  wrote
>
> >> I don't think a 319 (or possibly any of the Mk3 based EMU stock) would
> >> fit through the Loop.  The Mk3 design sticks further out at cantrail
> >> level than the 507/508 design, which is PEP-based and is narrower and
> >> lower at this point.  Clearance is at a premium in some places along
> >> the Loop tunnel, even for that stock.
>
> >But the eventual replacements for the 507/508 stock will undoubtedly be
> >purpose-built to fit the tunnels, and will be dual-voltage if Merseytravel's
> >aspirations to electrify Bidston - Wrexham, Hunts Cross - Warrington,
> >Kirkby - Wigan, and Ormskirk - Southport/Preston are to be achieved.
>
> Yes, of course you're right, Peter, but I was replying specifically to
> Paul Scott's point about the possibility of using refurbished
> ex-Thameslink Class 319 units on the Loop.
>
> Aside from the gauge problem, it would otherwise be an excellent idea.


One wonders if a varant of LU Bombardier S stock might fit ? Wider but
shorter ?

--
Nick

On 2 Jul, 17:20, Robert Wilson 
wrote:
>
> If he completes a circuit then you and he would know about it.
> Doubtless so would the rest of us on the news that night.
>
> Rob.

There's a report on the RAIB site about a driver wearing shorts who
sadly was electrocuted from a momentary contact on the leg.

On Wed, 2 Jul 2008 07:48:07 -0700 (PDT), John B 
wrote:

>On 2 Jul, 14:25, "R.C. Payne"  wrote:
>> > I don't like third rail anyway, it's scraggy way of collecting energy
>> > in my view.
>>
>> But then when was the last time you heard of train service being
>> disrupted because of 3rd rail issues?
>
>Happens on the Southern and on LUL most winters - 3rd rails don't like
>freezing. EMU breakdowns caused by broken shoes aren't unknown,
>either.
>
It also happens where heavy rain causes localised flooding while
nearby areas are relatively unaffected.

>> It is a good system for certain
>> purposes, such as metros where speeds are low and trains are frequent.
>
>Broadly agree, although if you were starting afresh today then
>something more like the DLR's protected contact rail would be good.
>
>> It was foolish of the Southern to have persisted with it beyond London
>> suburban areas, but if anything can be said of the system, it is reliable.
>
>Again, reliable-ish once you've made the enormous capital investment
>in transformers. In the Southern's defence, it's quite hard to know
>where you'd draw the line (eg on the SWML you've got a 4-track railway
>from Wimbledon to Brookwood with trains that run on the slows from
>Wimbledon all the way to Guildford, Basingstoke and Alton - you've not
>got the nice self-contained suburban vs urban boundary of the DC lines
>or the NLR...)
>
>> > Much better to have properly strung knitting, which the ECML has never
>> > had, because it was done on the cheap by BR with no gov money.
>>
>> Though the wires seem to keep coming down at places like Welwyn and
>> Stevenage, which were wired in the '70s, presumably to the same spec as
>> the northern part of the WCML, rather than the Peterborough -
>> Leeds/Edinburgh stretch done on the cheap in the '80s.  This seems to me
>> to be a problem of poor maintenance of trains and catenery rather than
>> an initial design problem.  After all, how often is the WCML delayed by
>> wires being pulled down in Carlisle?
>
>Not sure what the literal answer is - but it'd be interesting to see
>actual delay minutes attributable to wires-coming-down. My suspicion
>is that the obvious visibility of de-wirings compared with other track/
>signalling/train incidents means they're massively overstated as a
>cause of delay...

Tony Polson wrote:
> D7666  wrote:
> 
>> On Jul 2, 3:04 pm, Tony Polson  wrote:
>>
>>> It would make sense, though.  However, what happens when you get to
>>> Salisbury and start thinking about Exeter?
>>> I suppose that dual voltage stock could be used to enable 25kV OHLE to
>>> be installed west of Salisbury.
>> If west of Worting Jn were considered as a single scheme, or to
>> Salisbury with an optional future extension, all at one go, then it
>> would be logical to have it all as 25 kV. Only if Salisbury were dealt
>> with seperately under a ''no plans'' for Exeter scheme would third
>> rail make sense.
> 
> 
> Of course.  But I think that, in the real world, electrifying to
> Exeter would only be considered after electrification to Salisbury had
> already been completed.
> 
> 
>> One other factor these days to take into account is that existing
>> rolling stock of current generation (excuse the pun) with AC motors is
>> in effect already dual traction fitted or easily capable of
>> conversion. This would impact on the economics of extending the
>> Southern Electric zone by 25 kV.
> 
> 
> Indeed.  Does the conversion from DC to variable frequency AC consume
> a significant amount of power?
> 
Hi,
No not really.  Actually it's more proportionate to the frequency of the 
PWM because IGBT's do not tend to like running at high freqs.  The use 
of higher frequencies in an AC drive tend to improve control stability, 
and the audible noise footprint of said converter.

Losses are more or less a straignthline in proportion to PWM freq.  The 
Vce losses of IGBT's these is much better than it was even a few years ago.

Rob.

contrex wrote:
> On 2 Jul, 17:20, Robert Wilson 
> wrote:
>> If he completes a circuit then you and he would know about it.
>> Doubtless so would the rest of us on the news that night.
>>
>> Rob.
> 
> There's a report on the RAIB site about a driver wearing shorts who
> sadly was electrocuted from a momentary contact on the leg.
Yes it does'nt take alot when your playing with 750v.  Funnily enough 
750v is still considered low voltage in the trade.

Rob.

On Jul 2, 8:32 pm, Robert Wilson 
wrote:

> Yes it does'nt take alot when your playing with 750v.  Funnily enough
> 750v is still considered low voltage in the trade.

Or even 750 V.

--
Nick

In message 
          "Peter Masson"  wrote:

> 
> "Graeme Wall"  wrote
> >
> > In cold and snowy weather you can get severe arcing that can damage the
> > collector shoes leaving a train stranded.
> >
> It has been known for the arcing to weld the shoes to the conductor rail.
> When this happens on Sole Street bank it can end up with 5 hour delays.
> 

-- 
Graeme Wall
This address is not read, substitute trains for rail.
Transport Miscellany at <http://www.greywall.demon.co.uk/rail/index.html>

In message <80fbbb84f%Rail@greywall.demon.co.uk>
          Graeme Wall  wrote:

Nothing

Apologies, I got a phone call at the wrong moment and hit send instead of
cancel.


-- 
Graeme Wall
This address is not read, substitute trains for rail.
Transport Miscellany at <http://www.greywall.demon.co.uk/rail/index.html>

D7666  wrote:

>On Jul 2, 5:29 pm, Tony Polson  wrote:
>> "Peter Masson"  wrote:
>> >"Tony Polson"  wrote
>>
>> >> I don't think a 319 (or possibly any of the Mk3 based EMU stock) would
>> >> fit through the Loop.  The Mk3 design sticks further out at cantrail
>> >> level than the 507/508 design, which is PEP-based and is narrower and
>> >> lower at this point.  Clearance is at a premium in some places along
>> >> the Loop tunnel, even for that stock.
>>
>> >But the eventual replacements for the 507/508 stock will undoubtedly be
>> >purpose-built to fit the tunnels, and will be dual-voltage if Merseytravel's
>> >aspirations to electrify Bidston - Wrexham, Hunts Cross - Warrington,
>> >Kirkby - Wigan, and Ormskirk - Southport/Preston are to be achieved.
>>
>> Yes, of course you're right, Peter, but I was replying specifically to
>> Paul Scott's point about the possibility of using refurbished
>> ex-Thameslink Class 319 units on the Loop.
>>
>> Aside from the gauge problem, it would otherwise be an excellent idea.
>
>
>One wonders if a varant of LU Bombardier S stock might fit ? Wider but
>shorter ?


Sorry, I am not familiar with that stock.  Is it the new stock for the
Metropolitan and District Lines?

D7666  wrote:

>On Jul 2, 8:32 pm, Robert Wilson 
>wrote:
>
>> Yes it does'nt take alot when your playing with 750v.  Funnily enough
>> 750v is still considered low voltage in the trade.
>
>Or even 750 V.


Mind the gap!  ;-)

On Jul 2, 10:40 pm, Tony Polson  wrote:

> Sorry, I am not familiar with that stock.  Is it the new stock for the
> Metropolitan and District Lines?

Yep.

I've no idea on dimensions actual or c.f. 507/508.

More a cooment to stir things up in here !!!

--
Nick

Robert Wilson wrote:

> Chris Tolley wrote:
>> David Hansen wrote:
>> 
>>> On Wed, 2 Jul 2008 03:18:00 -0700 (PDT) someone who may be Ed the
>>> Amateur  wrote this:-
>>>
>>>> How many fatalities are there each year on parts of the network
>>>> powered by live rails as opposed to OHLs?
>>> Enough that new installations with unprotected conductor rails are
>>> not permitted (and have not been permitted for a long time), other
>>> than extensions to existing systems.
>> 
>> Really? One doesn't hear of many. Last Friday at Clapham Junction, I was
>> watching an orange-jacketed worker as he made his way across the tracks.
>> At one point, when he was only about five metres away from me, I would
>> swear that the back of his trousers brushed against a conductor rail as
>> he stepped over it. Nothing happened.
>> 
> If he'd got damp trousers then you would have seen some fireworks. 
> Depends on how high an impedance his boots are too.
> 
> If he completes a circuit then you and he would know about it. 
> Doubtless so would the rest of us on the news that night.

Well, that's what I've always understood, but er, put it this way, if
*I* ever had to cross an energised third rail, I would take rather
larger steps than this chap was doing. I was rather surprised at his
nonchalance.

-- 
http://gallery120232.fotopic.net/p9632967.html
(43 125 at London Paddington, 1978)

On Wed, 02 Jul 2008 15:54:25 GMT, Chris Tolley wrote:

> David Hansen wrote:
> 
>> On Wed, 2 Jul 2008 03:18:00 -0700 (PDT) someone who may be Ed the
>> Amateur  wrote this:-
>> 
>>>How many fatalities are there each year on parts of the network
>>>powered by live rails as opposed to OHLs?
>> 
>> Enough that new installations with unprotected conductor rails are
>> not permitted (and have not been permitted for a long time), other
>> than extensions to existing systems.
> 
> Really? One doesn't hear of many. Last Friday at Clapham Junction, I was
> watching an orange-jacketed worker as he made his way across the tracks.
> At one point, when he was only about five metres away from me, I would
> swear that the back of his trousers brushed against a conductor rail as
> he stepped over it. Nothing happened.

Many, many moons ago I attended some nightime technical tests at Watford.
At the conclusion of these those of us from outside the area made our way to
the PSB to ascertain the availability of transport 'back to base' (ie a
suitable northbound freight), or to seek a warm dry place, with a kettle, to
bed down until the first service train.

It wasn't long before the signalman announced that he had a liner train on
the board and had replaced the platform-end signal to stop it for us.  Two
of us departed for the station.  

The DC lines are immediately outside the PSB and lie between it and the
station (authorised walking route you say, what's one of those then?).  To
further complicate matters, the layout here contains various bits of complex
P&C, including possibly a scissors crossing (I can't remember exactly, but I
do recall there seemed to be an awful lot of ironwork around).  

In near darkness my colleague, a considerably older and more experienced
gentleman, set off at a smart walking pace, confidently stepping over the
nasty bits, and had almost reached the platforms whilst I was still picking
my way, *very* gingerly, through the maze of rails, and trying not to tangle
with anything hot.

From a 'trackwork' POV, I don't like third rail.  Never have, and never
will!
 
-- 
WZR

On Wed, 02 Jul 2008 20:32:04 +0100, Robert Wilson
 wrote:

>contrex wrote:
>> On 2 Jul, 17:20, Robert Wilson 
>> wrote:
>>> If he completes a circuit then you and he would know about it.
>>> Doubtless so would the rest of us on the news that night.
>>>
>>> Rob.
>> 
>> There's a report on the RAIB site about a driver wearing shorts who
>> sadly was electrocuted from a momentary contact on the leg.
>Yes it does'nt take alot when your playing with 750v.  Funnily enough 
>750v is still considered low voltage in the trade.
>
It is relatively "low" compared with the practical maximum of 440kV.

On Wed, 2 Jul 2008 11:28:03 -0700 (PDT) someone who may be D7666
 wrote this:-

>> Consideration was given to making the REPs dual voltage.
>
>Proof ???

B. K Cooper says pretty much that in "Electric trains in Britain".

>I'll put money on you will not find this anywhere except in uninformed
>fantasy ramblings.

Yawn.

It is true that he does not specifically mention REPs in the
paragraph (I thought he did but was misremembering), but it is at
the end of a section on Class 33s and REPs. The point he is making
is that the reduction of the cost of substations with 1500V (by
halving the number of them) would be outweighed by the cost of more
stock due to lack of flexibility, plus the problems of shoegear. He
also makes the point that the introduction of silicon rectifiers
allowed the number of substations to be reduced anyway, 13 between
Basingstoke and Bournemouth instead of 16 if they had been
mercury-arc ones.

He then goes on to mention that twelve coach trans plus locomotives
would not fit in the platforms at Waterloo and light locomotive
movements at peak hours would not be welcome, hence the method of
working adopted.

So, I'll say, "Consideration was given to making the Bournemouth
Electrification dual voltage.", and leave it at that.



-- 
  David Hansen, Edinburgh 
 I will *always* explain revoked encryption keys, unless RIP prevents me
 http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

WZR wrote:

>Many, many moons ago I attended some nightime technical tests at Watford.

>The DC lines are immediately outside the PSB and lie between it and the
>station (authorised walking route you say, what's one of those then?).  To
>further complicate matters, the layout here contains various bits of complex
>P&C, including possibly a scissors crossing (I can't remember exactly, but I
>do recall there seemed to be an awful lot of ironwork around).  
>
>In near darkness my colleague, a considerably older and more experienced
>gentleman, set off at a smart walking pace, confidently stepping over the
>nasty bits, and had almost reached the platforms whilst I was still picking
>my way, *very* gingerly, through the maze of rails, and trying not to tangle
>with anything hot.
>
>From a 'trackwork' POV, I don't like third rail.  Never have, and never
>will!
> 
So long ago that it seems like another age, I was involved in
regular night time testing of the Brush/GEC class 314 prototype
(converted from a 2-car PEP) on LTS.

The Brush and RTC contingent would rendezvous at Loughborough
station to catch the latest possible train to St Pancras, then
make our way to East Ham.  It would still be far too early for
our midnight start, so the adjacent Indian restaurant was our
next call, followed for some by a cooling lager.

By this time, the last up train would have run, so only the down
platform was open.  We marched onto the station, donning our
hi-vi as we went, straight off the ramp and across the
underground lines.  Stepping gingerly over two singles and a
double - rather like show jumping, the doubles were the hardest. 
One of the BR guys (ex SR) was much more at home, but being
rather short confessed to being concerned about catching the back
of his standard-issue coat on a wet night.

All we had to do then was cross the LTS running lines and we were
on route to the depot, ready to spend the night shuttling between
East Ham and Southend.

Chris

D7666 wrote:
> On Jul 2, 8:32 pm, Robert Wilson 
> wrote:
> 
>> Yes it does'nt take alot when your playing with 750v.  Funnily enough
>> 750v is still considered low voltage in the trade.
> 
> Or even 750 V.
> 
> --
> Nick
Yes thank you for that.  An old boss of mine was very particular about 
such things so I should know better.

Rob.

Robert Wilson wrote:
> amogles@yahoo.com wrote:
>> On 2 Jul., 15:28, "R.C. Payne"  wrote:
>>
>>> Though the fact that ac electrification is single phase can cause
>>> trouble with balancing the load across the three phases, as an express
>>> train is a very large unbalanced load.  On dc systems, the substation
>>> load is balanced across all three phases.
>>
>> That is, if the railway is fed from a single phase. Of course if you
>> use a rotary converter or the static-state equivalent then you load
>> all three phases equally. This is done for example on 16.7Hz systems
>> such as in Germany and Switzerland, but could theoretically also be
>> done for 50Hz systems.
> There was an earlier discussion about load balancing on OHLE systems and 
> is appears that mostly they distribute over different supply phases like 
> domestic final distribution at street level.  Ie, every third house 
> being on the red phase etc.

Though what is the load provided by a single house?  It is unlikely that 
you will have all the "red" houses drawing lots of current while the 
yellow and blue ones sit there dormant.  On the other hand, with a 
single train drawing as much as 3 MW routinely, and every possibility of 
no balancing trains on the other phases, the degree of imbalance is much 
greater for a railway than for a domestic situaion.  Clearly (by 
demonstration) it is possible to deal with this problem, but it is a 
problm that DC systems to not exhibit.

Robin

Charles Ellson wrote:
> On Wed, 02 Jul 2008 20:32:04 +0100, Robert Wilson
>  wrote:
> 
>>contrex wrote:
>>>On 2 Jul, 17:20, Robert Wilson 
>>>wrote:
>>>>If he completes a circuit then you and he would know about it.
>>>>Doubtless so would the rest of us on the news that night.
>>>>
>>>>Rob.
>>>There's a report on the RAIB site about a driver wearing shorts who
>>>sadly was electrocuted from a momentary contact on the leg.
>>Yes it does'nt take alot when your playing with 750v.  Funnily enough 
>>750v is still considered low voltage in the trade.
>>
> It is relatively "low" compared with the practical maximum of 440kV.

When I (briefly) worked in the high voltage industry, we (corporate) had 
supplied 525 kV, but systems above about 400 kV are uncommon.  I didn't 
deal with the subsea side of things, where high voltage DC is often 
used, and I don't know how high they went.

Note that these voltages are all between phases, not from phase to 
earth, which is a factor of SQRT(3) less, so doesn't sound so impressive.

Robin

R.C. Payne wrote:
> Robert Wilson wrote:
>> amogles@yahoo.com wrote:
>>> On 2 Jul., 15:28, "R.C. Payne"  wrote:
>>>
>>>> Though the fact that ac electrification is single phase can cause
>>>> trouble with balancing the load across the three phases, as an express
>>>> train is a very large unbalanced load.  On dc systems, the substation
>>>> load is balanced across all three phases.
>>>
>>> That is, if the railway is fed from a single phase. Of course if you
>>> use a rotary converter or the static-state equivalent then you load
>>> all three phases equally. This is done for example on 16.7Hz systems
>>> such as in Germany and Switzerland, but could theoretically also be
>>> done for 50Hz systems.
>> There was an earlier discussion about load balancing on OHLE systems 
>> and is appears that mostly they distribute over different supply 
>> phases like domestic final distribution at street level.  Ie, every 
>> third house being on the red phase etc.
> 
> Though what is the load provided by a single house?  It is unlikely that 
> you will have all the "red" houses drawing lots of current while the 
> yellow and blue ones sit there dormant.  On the other hand, with a 
> single train drawing as much as 3 MW routinely, and every possibility of 
> no balancing trains on the other phases, the degree of imbalance is much 
> greater for a railway than for a domestic situaion.  Clearly (by 
> demonstration) it is possible to deal with this problem, but it is a 
> problm that DC systems to not exhibit.
> 
> Robin
No actually even domestic supplies tend to balances out.  A house is 
restricted to 22kW based on the supply being 220V and the Consumer Unit 
current being 100A or thereabouts.

Even on a Railway, there will be sufficient traffic to balance out the 
load.  The network is designed with these requirements in mind.  There 
are special transformers around that help in this regard.

The people who were involved in the original correspondence can help 
here...if only I could remember their names.

Sincerely,
Rob.

R.C. Payne wrote:
> Charles Ellson wrote:
>> On Wed, 02 Jul 2008 20:32:04 +0100, Robert Wilson
>>  wrote:
>>
>>> contrex wrote:
>>>> On 2 Jul, 17:20, Robert Wilson 
>>>> wrote:
>>>>> If he completes a circuit then you and he would know about it.
>>>>> Doubtless so would the rest of us on the news that night.
>>>>>
>>>>> Rob.
>>>> There's a report on the RAIB site about a driver wearing shorts who
>>>> sadly was electrocuted from a momentary contact on the leg.
>>> Yes it does'nt take alot when your playing with 750v.  Funnily enough 
>>> 750v is still considered low voltage in the trade.
>>>
>> It is relatively "low" compared with the practical maximum of 440kV.
> 
> When I (briefly) worked in the high voltage industry, we (corporate) had 
> supplied 525 kV, but systems above about 400 kV are uncommon.  I didn't 
> deal with the subsea side of things, where high voltage DC is often 
> used, and I don't know how high they went.
> 
> Note that these voltages are all between phases, not from phase to 
> earth, which is a factor of SQRT(3) less, so doesn't sound so impressive.
> 
> Robin
Where were you working with 525kV?  Nothing like that here is there?

Rob.

Robert Wilson wrote:
> R.C. Payne wrote:
>> Charles Ellson wrote:
>>> On Wed, 02 Jul 2008 20:32:04 +0100, Robert Wilson
>>>  wrote:
>>>
>>>> contrex wrote:
>>>>> On 2 Jul, 17:20, Robert Wilson 
>>>>> wrote:
>>>>>> If he completes a circuit then you and he would know about it.
>>>>>> Doubtless so would the rest of us on the news that night.
>>>>>>
>>>>>> Rob.
>>>>> There's a report on the RAIB site about a driver wearing shorts who
>>>>> sadly was electrocuted from a momentary contact on the leg.
>>>> Yes it does'nt take alot when your playing with 750v.  Funnily 
>>>> enough 750v is still considered low voltage in the trade.
>>>>
>>> It is relatively "low" compared with the practical maximum of 440kV.
>>
>> When I (briefly) worked in the high voltage industry, we (corporate) 
>> had supplied 525 kV, but systems above about 400 kV are uncommon.  I 
>> didn't deal with the subsea side of things, where high voltage DC is 
>> often used, and I don't know how high they went.
>>
>> Note that these voltages are all between phases, not from phase to 
>> earth, which is a factor of SQRT(3) less, so doesn't sound so impressive.
>>
> Where were you working with 525kV?  Nothing like that here is there?

While there was no 525 kV stuff while I was working there, the company 
had supplied some in the past to somewhere in the US, I think Washington 
State in connection with some sort of hydro project.  I saw photographs 
of the equipment under test.

Robin

"John B"  wrote in message 
news:6a1c8e7e-e967-4ea8-bf3f-1fa5731ec6f1@m73g2000hsh.googlegroups.com...
> On 2 Jul, 14:25, "R.C. Payne"  wrote:
>>
>> But then when was the last time you heard of train service being
>> disrupted because of 3rd rail issues?
>
> Happens on the Southern and on LUL most winters - 3rd rails don't like
> freezing. EMU breakdowns caused by broken shoes aren't unknown,
> either.
>
I once spent a long night in a 4XX unit that lost a shoe - the departing 
shoe punched a hole in the braking system and we shuddered to halt, and 
remained there for about 3 hours.

The new generation of units seem to be a lot more resistant to icy weather, 
maybe because they have twice as many collector shoes than the types they 
replaced. OTOH we probably haven't had the wrong kind of snow in the last 3 
years.

D A Stocks

On Wed, 02 Jul 2008 15:54:25 GMT, Chris  Tolley 
wrote:

>Really? One doesn't hear of many. Last Friday at Clapham Junction, I was
>watching an orange-jacketed worker as he made his way across the tracks.
>At one point, when he was only about five metres away from me, I would
>swear that the back of his trousers brushed against a conductor rail as
>he stepped over it. Nothing happened.

I assume it was dry weather.  If it had been raining, he would have felt
it (but lived to tell the tale).

Most people who work or have worked on the 3rd rail have received belts,
but anything that actually injures is rare.  I had several; the worst
was in the pouring rain when water coming off my long overcoat made
contact with the juice rail.  The current must have run up the (rubber)
mac as it felt as if somebody had hit me in the back of the neck. I
suppose that if it had been a lot stronger and knocked me off my feet it
could have been a lot worse, but as it was I confined myself to a few
expletives and just carried on.

However, knowing what 750v can do, I would be most reluctant to work on
a system where it was much higher.  750v seems to be a good compromise
between performance and safety, and the third rail has proved an
excellent system for suburban systems over the last 100 years. But it
isn't suitable for speeds over 90mph, and is best suited to 75mph or
less.



-- 
Bill Hayles
http://www.rossrail.com
md@rossrail.com

On Jul 3, 8:12 am, David Hansen 
wrote:

> It is true that he does not specifically mention REPs in the
> paragraph (I thought he did but was misremembering), but it is at
> the end of a section on Class 33s and REPs. The point he is making
> is that the reduction of the cost of substations with 1500V (by
> halving the number of them) would be outweighed by the cost of more
> stock due to lack of flexibility, plus the problems of shoegear. He
> also makes the point that the introduction of silicon rectifiers
> allowed the number of substations to be reduced anyway, 13 between
> Basingstoke and Bournemouth instead of 16 if they had been
> mercury-arc ones.
>
> He then goes on to mention that twelve coach trans plus locomotives
> would not fit in the platforms at Waterloo and light locomotive
> movements at peak hours would not be welcome, hence the method of
> working adopted.
>
> So, I'll say, "Consideration was given to making the Bournemouth
> Electrification dual voltage.", and leave it at that.

Indeed,
but all the above were the reasons on balance that eliminated AC/DC
and 750/1500 V working prior to decisions about push-pull working.
Decisions taken in or around 1961 - Reps were not worked out until
1963/1964.


--
Nick

In article <g4ii9a$ge5$1@news.albasani.net>, David A Stocks
 scribeth thus
>
>"John B"  wrote in message 
>news:6a1c8e7e-e967-4ea8-bf3f-1fa5731ec6f1@m73g2000hsh.googlegroups.com...
>> On 2 Jul, 14:25, "R.C. Payne"  wrote:
>>>
>>> But then when was the last time you heard of train service being
>>> disrupted because of 3rd rail issues?
>>
>> Happens on the Southern and on LUL most winters - 3rd rails don't like
>> freezing. EMU breakdowns caused by broken shoes aren't unknown,
>> either.
>>
>I once spent a long night in a 4XX unit that lost a shoe - the departing 
>shoe punched a hole in the braking system and we shuddered to halt, and 
>remained there for about 3 hours.
>
>The new generation of units seem to be a lot more resistant to icy weather, 
>maybe because they have twice as many collector shoes than the types they 
>replaced. OTOH we probably haven't had the wrong kind of snow in the last 3 
>years.
>

No we've hardly had any snow for quite some time now, at least around
this way the snow of what was it.. 13st Jan 2005 caused absolute
gridlock in South Cambs and that was only half an inch or so...

I bet some accountant has worked out it would be cheaper to shut the
networks down rather than try to run them;!...

-- 
Tony Sayer

Robert Wilson wrote:
> R.C. Payne wrote:
>> Robert Wilson wrote:
>>> amogles@yahoo.com wrote:
>>>> On 2 Jul., 15:28, "R.C. Payne"  wrote:
>>>>
>>>>> Though the fact that ac electrification is single phase can cause
>>>>> trouble with balancing the load across the three phases, as an express
>>>>> train is a very large unbalanced load.  On dc systems, the substation
>>>>> load is balanced across all three phases.
>>>>
>>>> That is, if the railway is fed from a single phase. Of course if you
>>>> use a rotary converter or the static-state equivalent then you load
>>>> all three phases equally. This is done for example on 16.7Hz systems
>>>> such as in Germany and Switzerland, but could theoretically also be
>>>> done for 50Hz systems.
>>> There was an earlier discussion about load balancing on OHLE systems 
>>> and is appears that mostly they distribute over different supply 
>>> phases like domestic final distribution at street level.  Ie, every 
>>> third house being on the red phase etc.
>>
>> Though what is the load provided by a single house?  It is unlikely 
>> that you will have all the "red" houses drawing lots of current while 
>> the yellow and blue ones sit there dormant.  On the other hand, with a 
>> single train drawing as much as 3 MW routinely, and every possibility 
>> of no balancing trains on the other phases, the degree of imbalance is 
>> much greater for a railway than for a domestic situaion.  Clearly (by 
>> demonstration) it is possible to deal with this problem, but it is a 
>> problm that DC systems to not exhibit.
>>
>> Robin
> No actually even domestic supplies tend to balances out.  A house is 
> restricted to 22kW based on the supply being 220V and the Consumer Unit 
> current being 100A or thereabouts.
> 
> Even on a Railway, there will be sufficient traffic to balance out the 
> load.  The network is designed with these requirements in mind.  There 
> are special transformers around that help in this regard.
> 
> The people who were involved in the original correspondence can help 
> here...if only I could remember their names.
> 
> Sincerely,
> Rob.

The UK 25kV ac OLE network does *not* have any specific measures to 
load-balance, other than the previously mentioned alternating of the 
phase connections at consecutive feeder stations along the route. The 
imbalance is limited to something like 0.5% by the national grid 
companies, although I believe the railway exceeds these limits on 
occasion at specific high load locations. Phase balancers are 
*available*, but are expensive and not used in the UK. I believe they 
are on other railways.

As others have stated, the DC network is load-balanced by the use of a 
three phase ac supply rectified to DC.

> >David Hansen wrote:
>
> I suspect that there are none written down, BICBW.
>
> However, I think that the Railway Inspectorate would have something
> to say about the reasonableness of extending conductor rails from
> say Watford Junction to Liverpool South Parkway. I imagine the
> phrase, "taking the piss", would feature prominently in private.
>
> Safety is a subject which revolves around what is reasonable and
> practical.
I would suggest Watford Stoke Man Picc Warrington Central Hunts Cross
would work better.

Bill Hayles wrote:

> On Wed, 02 Jul 2008 15:54:25 GMT, Chris  Tolley 
> wrote:
> 
>> Last Friday at Clapham Junction, I was watching an orange-jacketed
>> worker as he made his way across the tracks. At one point, when he
>> was only about five metres away from me, I would swear that the back
>> of his trousers brushed against a conductor rail as he stepped over
>> it. Nothing happened.
> 
> I assume it was dry weather.  

Yes, it was. 

<snip interesting comments>

-- 
http://gallery120232.fotopic.net/p12598505.html
(25 124 and 25 168 at Nuneaton, 20 Apr 1980)

On 3 Jul, 22:53, Hans-Joachim Zierke  wrote:
> than a big toy train. As soon as you want real acceleration with long
> passenger trains, or want to move real freight trains, the amperage gets
> too

In English, one says "current".

HTH, HAND.

--
John Band
john at johnband dot org
www.johnband.org