OHLE 25kV or 750V DC third-rail

[Jordy]

It's also cos French overhead takes a different pan tension to ours (i can't remember whether it is higher or lower).

I think its Higher - but i'm not sure why :?

Jordy

 

[tramboy]

Having had a quick look around the internet, and a think...French high speed lines have a pan tension which is higher, as the level of overhead never changes (ie TGVs run with the pan at a fixed height whilst on high speed lines) giving a constant contact pressure of 70N.

On British rail, and every other domestic line (including France) pan tension has to vary, along with height, as the contact wire is either higher or lower depending on crossings and the like.

Regards

Dave

 

[Tom B]

OHLE. Safer (you're more likely to be near a 3rd rail and slip - you'd need to be deliberately up there to get a shock from the OHLE) and faster. Plus it's more standard - I'm surprised the remaining 3rd rail systems haven't been converted yet - nonstandard OHLE (such as Newcastle, LTS and Woodhead) have long since gone.

 

[Simming]

Arc-ing, so its called, is more commen on 3rd rail than it is on OHLE. OHLE arcing Is only really noticeable at night, and is usually only happends where two lengths of OH wire are connected, by that solid metal frame thingy.

 

[TomCrame]

Over head, safer, and you get better trains running of it (92s 8) )

But as 92's are dual voltage, your argument falls down immediately.

 

[Julian G]

Another thing - I was standing at Stratford. A 10 coach mk2 90 formation passed. When the 90 passed, it emitted a huge spark and it smelt really bad. That is one disadvantage of OHLE!

Pendos do it at Harrow too, they spark a lot

 

[Sprog]

The sparking is caused by dirty contact (panto/overhead) and it also can occur at neutural sectons, where current tries to arc across from one live section to another...

When i first encountered OHLE at brimingham new street when i was a child, i was quite fearfull of it, especially after being told how much current was flowing through it. I also cringe at the sight of trackworkers stepping over 3rd rails like it isnt even there. On one occasion at Ramsgate stn. i have seen the bottom of a PW workers trousers brush the live rail but thankfully, they where non-conductive.

I'd have to say OHLE. But not the crap stuff that BR put on the ECML.

The CTRL is an example of how well OHLE can be constructed well and be efficient. Out of curiosuty, does anyone know if there have been any line-down incidents on CTRL 1 yet??

I think both though, are suited to their purpose. The LU for example, is a good example of use of 3rd rail, as is the South-London suburban network.

 

[Tom C]

The major problem with 3rd Rail is the introduction of new units with a branch of Dixons attached to it. 357's are running extreamly well now they have had time to settle down but 375's & 377's (especially 377's) are all still miles behind the 357's and a million miles behind the 400 series stock they replaced and this is after an enomous power supply upgrade. All this technology is an enormous strain on the system and the same goes for Desiro's which are now less reliable than the 377's hock:

Voted for 3rd Rail because it means no ugly power lines and you don't get an endless hum throughout your journey just nice musical traction motor unless it is a Electrostar, Networker or Desiro.

 

[NumptyDriver]

It's when you touch the running & conductor rails at once that you want to be worried hock: .

Running rails have pretty much no electricity in them at all - only a few volts to operate the track circuits.

not necessarily - all it takes is one broken traction return current bond and you'd be toast before you knew it.

i have to say third rail is a primitive, dangerous thing, not at all eco-friendly and it seems every week stories are in the paper about kids being electrocuted by live rails, not to mention the wildlife. it must be like driving round a morgue. ohle is much safer and more advanced, yes it will arc up to 9 feet (nearly 3 metres) but only if conditions are absolutely right, which is rare, otherwise it'd be arcing all over and trains would never get anywhere. i have seen with my own eyes many things which have bit the dust after coming to grief on the third rail, but only ever seen one thing electrocuted by ohle. Also because it's a lower voltage compared to ohle and third rails ore often made of aluminium (relatively poor conductor of electricity) as opposed to the copper used on ohle, energy is lost as heat. This is why electricity transmitted in pylons on the national grid is often 440,000v or 275,000v to save enegry waste. Indeed, one of the old rules questions used to be 'how do you recognise the third rail in third rail areas?' to which there were a number of answers, one of which was 'it is warm to the touch' (obviously when the juice has just been switched off, otherwise that would be a bit of an understatement).

 

[metrocammel]

I voted OHLE, I agree that is it "safer" than Third Rail, for the obvious reasons you can't get frazzled by OHLE unless you jump off a bridge onto the wires (and even then your OK until you earth yourself by attempting to climb down!) whereas with 3rd rail, it takes an idiot to retrieve his football or somthing, and your a gonner.

So, really 3rd rail is a bit archiaic, and I'm surprised the Southern system has been retained, but I imagine the costs to install overhead would be rather phohibitive. But I cant imagine, once the "plastic" era of EMU's are due to be withdrawn in what... 20 years say (if they can last that long!) ... 3rd rail will be on it's last legs.

I suppose the way forward is some sort of electricity transfer with no "bare" contacts that cant cause electrocution. Though, I wonder why they have never used a "conduit" system on the mainline, like the Feltham trams had for central London working, that appeared to be a pretty safe, fool-proof system?- and the conduits can still be seen in London - on the northern slope of the Kingsway tram tunnel, which leads onto Southampton Row if I remember correctly... near Holborn

 

[TheSlash]

Numpty driver, i strongly disagree with your post regarding 3rd rail.
I work with the 3rd rail every day, the last time i heard of anybody being eletrocuted by it was at least a year ago. I read the paper most days and watch the daily national and local news broadcasts on tv
Yes wildlife does come to grief with it, but this is rare and most certainly not like a morgue.
The 3rd rail is very rarely made of aluminium. My job covers from Ashurst in the New Forest, across to Portchester which is near Portsmouth, up through Eastleigh and Winchester to Micheldever and we only have 1 short stretch of ally con rail, which is a single line between Fareham and Botley, on the Portsmouth to Eastleigh branch
As for hot to touch, it's normally the same temperature as the running rails, even when its switched on.
At least 3rd rail doesn't stop the job everytime the wind gets up abit
If i am doing work close to the 3rd rail and i don't feel happy with the safety situation, i can put a plastic cover over 3 of the 4 faces of the con rail {top and sides}, i can then do the job without worrying about the con rail, when i am finished, or called out for a train, i can simply lift the cover off and walk away.
I hold full AC and DC PTS, but i am much happier working on 3rd rail lines because i know that if i treat the 3rd rail properly, it will leave me alone.

 

[ChrisM]

3rd rail for me as i grew up watching it take over my local non-electricfied lines,also looks neater.

 

[Tomnick]

Apart from anything else - can you imagine wiring the approches to the likes of London Bridge and Waterloo with OHLE? That could be a minor nightmare!

 

[AlexS]

Well, part of Clapham Junction was done, Birmingham New Street is all done and so on, so it's challenging, but certainly possible!

 

[Tomnick]

Oh yeah, it's possible! Neither Clapham Junction nor New Street really come too close to some South London locations in terms of complexity though! Also bear in mind that there's a complex network as opposed just the few key routes on most electrification schemes - there's a surprisingly high number of route miles.

 

[Coxster]

Well, part of Clapham Junction was done, Birmingham New Street is all done and so on, so it's challenging, but certainly possible!

Only the LBSCR route was done which is only four platforms (don't think the WLL connection was around all those years ago) so that isn't really as challenging as it first sounds.

 

[Ascot]

Overhead i say but none electric is my option with the added "ying ying clang clang" noise

 

[Tom B]

I suppose the way forward is some sort of electricity transfer with no "bare" contacts that cant cause electrocution.

And how is the electricity meant to be transferred? Two contacts must touch each other in order for the electricity to flow - it's a simple as that!

 

[Tomnick]

What about transformers? There's no electrical connection between the two coils in a transformer!

 

[voyagerdude220]

I was equally drawn between the two options, but I have voted for 3rd rail, simply because overhead wires IMO often look a mess, but 3rd rail doesn't.

As for sparks.. I personally think that the biggest/worse spark I've seen was from a 3rd rail EMU, although I'm not sure.

 

[Tom B]

What about transformers? There's no electrical connection between the two coils in a transformer!

Pass us a slice of humble pie... I'd forgotten about using magnetism. Err why am I doing Electrons & Photons?

Though would electricity transfer by magnetism be practical in such a situation?

 

[Met Driver]

Though would electricity transfer by magnetism be practical in such a situation?

You'd need one heck of a coil wouldn't you (in place of the wires)...

 

[Techniquest]

OHLE for me if I have to have electrics. There's something with third rail I don't like. What I don't know. It seems like the baby, kiddy, immature to do electrification. Which might not make sense to you, but that's the best way to describe my feelings on third rail.

Mind, OHLE makes it impossible to get a decent, clear 3/4-profile from the top shot. From a bridge, OHLE really buggers up the shot. But that's being fussy.

In any case, I still prefer my diesels.

 

[TheSlash]

In any case, I still prefer my diesels.

Carrot cruncher

 

[Techniquest]

EH?! Never heard that term before!

But diesels still reign supreme overall, more so when it comes to freight.

Note the fact this is opinion...

 

[O L Leigh]

Hi Gang!!

There's no reason why OHLE needs to be ugly. The only reason is that it has been designed by engineers to be cheap to build and easy to maintain. However, there are no practical reasons why the lineside structures couldn't be more "sculptural".

If I remember my A-Level Physics, electric traction using magnetic induction would be expensive and even more risky than using OHLE. The strength of the magnetic fields and the size of the coils required to generate sufficient traction current would be enormous and would cause problems with electrical and electro-magnetic interference.

Probably the best way forward is to do away with on-train traction equipment altogether and have a system that drives a low-friction vehicle along a trackway. A Maglev system similar to the one in China is currently the best option using existing technology. It would be an ideal basis for high speed passenger services. On the downside, it wouldn't work as an integrated passenger and freight transport system in the same way as the current railways do.

Thoughts...?

one TN

 

[Techniquest]

Interesting idea, but as you say it wouldn't integrate so well as the current system does. Would be interesting to see Maglev-style routes here. Would take the boredom out of the ECML! London to Edinburgh would be so much quicker!

 

[Nick W]

Hi Gang!!

There's no reason why OHLE needs to be ugly. The only reason is that it has been designed by engineers to be cheap to build and easy to maintain. However, there are no practical reasons why the lineside structures couldn't be more "sculptural".

The OHLE on the ONE WA lines seems to look nicer than the GEML. Do you know why it is. I asume that they were more interested in making it look better for your lines.

If I remember my A-Level Physics, electric traction using magnetic induction would be expensive and even more risky than using OHLE. The strength of the magnetic fields and the size of the coils required to generate sufficient traction current would be enormous and would cause problems with electrical and electro-magnetic interference.

Probably the best way forward is to do away with on-train traction equipment altogether and have a system that drives a low-friction vehicle along a trackway.

Yes, it would definitely be better to use a linaer motor to propel the train and then use magnetic induction to power train doors, screens, heating, air con etc.

A Maglev system similar to the one in China is currently the best option using existing technology. It would be an ideal basis for high speed passenger services. On the downside, it wouldn't work as an integrated passenger and freight transport system in the same way as the current railways do.
Thoughts...?

With passenger levels rising and if the predictions for increaed frieght by 2020 are correct we might as well have some passenger only networks to creae room for more freight.

As for in intergrated why not have something like this:

Steel on Steel rail | Platform | Maglev | Platform | Steel on Steel | Platform | Maglev | Platform | Cycle lane | Curve | Bus/tram lane | Curve | Bus/tram lane | Curve | Bus/tram lane | Curve | Bus/tram lane | Curve | Cycle lane | Platform | Maglev | Platform | Steel on Steel | Platform | Maglev | Platform | Stee on Steel

Sure it would cost a lot for the fly overs, dive unders, road cycle ramps but it would be intergrated.

The platform can have stairs or esculators with a ramps for bikes and lifts for disabled to a concourse below.

High capacity interchange or what?

Of course it relies on public transport being free or guards on every train to check tickets.

 

[O L Leigh]

The OHLE on the ONE WA lines seems to look nicer than the GEML. Do you know why it is. I asume that they were more interested in making it look better for your lines.

Not at all. The design of OLE has never taken aesthetics into account, which is my point.

Exactly which bit of the WA are you comparing to what part of the GE? Half the problem with each sector is that electrification was done in stages. LST to Shenfield and eventually to Southend was the old 1500V DC system. From Shenfield to Colchester and from Bethnal Green up the WA to Chingford, Enfield, Hertford and Bishops Stortford via Seven Sisters only was all done to 25kV AC during the 1960's (at which time the old 1500V DC system was converted). The rest was all done progressively during the 1980's and 90's. Consequently it is all a hotch-potch mix of old and new, with lattice gantries or round post stanchions carrying both stitched and compound wiring rubbing up against the more modern simple system on "H" section masts or headspan structures. None of it is pretty and all of it is designed with one purpose in mind; to transmit power to the trains.

And this is my point. For a few bob more, the railways could design and install a better designed system of OLE that could be both more pleasing to the eye and, just possibly, more robust. It could be something that would enhance the landscape and the railway architecture as well as serving it's more mundane purpose.

one TN

 

[Nick W]

Hmm I've only seen the OHle from Stansted to Totenham Hale, comparing to ipswich to colchester.