Possible third rail electrifications

[GRALISTAIR]

A standalone system like Merseyrail will never change from being completely DC to mixed power.

Never, never say never again. That is what I was taught. A very bold statement indeedico

 

[mr_jrt]

@Gareth

There's other factors to consider as well though - take cost savings from regenerative braking. AC sections are much, much longer, meaning that the power generated is much, much more likely to have a train drawing power at that moment than a much shorter DC section would. This is greatly exacerbated by the low frequencies (by metro standards) of most of the Merseyrail branches. That's my point about OHLE trimming the outer reaches of the 3rd rail areas. They're spaced out, infrequent, and would be much, much better using OHLE than DC.

 

[mcnw35282]

The infrastructure has survived for 112 years with very little issue...so again I ask why fix it if it ain't broke? The money wasted on converting Merseyrail could be better spent electrifying another diesel line more worthy. Electrification schemes are being held back, or worse cancelled altogether because of a lack of funds. Merseyrail works just fine on DC...and has done for over a century.

 

[Philip Phlopp]

Oh dear indeed but not worth responding to considering you're calling people 'third rail fanatics'. You need to read what's actually been said before throwing such barbs.

You've not actually addressed the small matter of you being wrong about possible conversion of part of MerseyRail to 25kV AC being actively investigated by Network Rail.
--- old post above --- --- new post below ---

The infrastructure has survived for 112 years with very little issue...so again I ask why fix it if it ain't broke? The money wasted on converting Merseyrail could be better spent electrifying another diesel line more worthy. Electrification schemes are being held back, or worse cancelled altogether because of a lack of funds. Merseyrail works just fine on DC...and has done for over a century.

Not this yet again.

Life expired DC third rail grid and feeder systems are expensive to replace and relatively expensive to maintain, even with the very latest solid state components, because you've got so many of them to feed every few miles of track. Track maintenance is outrageously expensive when there's third rail and it causes all manner of signalling problems which leads to lower route reliability.

It's now possible to convert lines from 750V DC to 25kV AC and save money in the process, new 25kV feeding arrangements are cheaper than 750V DC like for like, whilst track maintenance becomes cheaper and reliability increases, covering the cost of installing the catenary itself.

We do need to be considering building up a dedicated conversion team though so as to not drain resources from electrification of 'diesel routes'.

 

[Gareth]

Never, never say never again. That is what I was taught. A very bold statement indeedico

Thanks but one I'm more than confident in.

 

[XDM]

Yet current 25kv electrification is outrageously expensive,almost prohibitively so,compared to the past,& it's not just Mr Ford who says so.
Why is it claimed 3rd rail track maintenance is costly? The power can be switched off & track machines can work with a third rail in the way.
Colour light signalling & third rail got along fine together under the Southern railway from the early 1930's & then BR. Signal failures were very rare or not remarked on as a problem.
I would be very interested in electrical engineers,& others, view on the following,which I accept is just a hypothesis from a non electrical engineer.
Every third rail dips towards the ballast when it ends so the shoe can rise up on it. Very many of this dips touch & are surrounded by ballast. Also footballs in urban areas end up bridging the third rail & the ballast. No problem in dry weather but when ballast & footballs are wet surely the current will leak to earth. I have seen steam rising from a third rail touching wet ballast. A year or so ago a Network Rail big wig said he was shocked by third rail power consumption. Is it because NR are boiling water everywhere because ballast is allowed to cover the sides of third rail?

 

[najaB]

Yet current 25kv electrification is outrageously expensive,almost prohibitively so,compared to the past,& it's not just Mr Ford who says so.

GWML electrification has been expensive. In Scotland, not so much so.

 

[Gareth]

@Gareth

There's other factors to consider as well though - take cost savings from regenerative braking. AC sections are much, much longer, meaning that the power generated is much, much more likely to have a train drawing power at that moment than a much shorter DC section would. This is greatly exacerbated by the low frequencies (by metro standards) of most of the Merseyrail branches. That's my point about OHLE trimming the outer reaches of the 3rd rail areas. They're spaced out, infrequent, and would be much, much better using OHLE than DC.

The argument isn't that 3rd rail is better per se; it's whether the supposed benefits of OHLE are worth the faff of partially converting a currently whole 3rd rail system and all the works and disruption that would entail plus trains having to change power when they didn't have to previously. Unless there's intention to run onto lines shared with other services (say extend Chester to Crewe for argument's sake) then I feel the benefits are probably marginal, so I'll be keeping my chips on black.

What I hope most can at least agree on is that the different lines and local systems need looking at specifically and decisions on things such as this made with awareness to local circumstance. What's good for the goose probably is good for the gander most of the time but not necessarily so for a different animal. Merseyrail's quite a different animal to much of the already heterogeneous National Rail network and arguments for changing certain lines in the South East won't necessarily follow even for other lines in the South East, let alone Merseyrail. A dogmatic 'one size fits all policy' would not be a good way to go on this.

 

[najaB]

The argument isn't that 3rd rail is better; it's whether the supposed benefits of OHLE are worth the faff of partially converting a currently whole 3rd rail system and all the works and disruption that would entail plus trains having to change power when they didn't have to previously...

As posted up-thread by a number of posters, there is a presumption against new 3rd rail installations so the argument is about making the case that 3rd rail will have significant enough advantages over an overhead solution to outweigh its efficiency and safety shortcomings. Infill and short extensions of existing systems likely will, but larger-scale extensions (or new lines) almost certainly won't.

And that 'faff' you refer to has been shown to be very little faff at all in existing installations.

 

[XDM]

A third rail benefit which I omitted to flag up in my last post; DC units don't have to drag 2 tonnes of transformer per 4 cars up hill & down dale.
Perhaps there are a thousand 4 car equivalent DC units in the UK. That's 2,000 tons to be dragged around,accelerated & braked all the time,if DC went to AC. The extra energy & rail wear cost?
And since a recent poster mentioned the high cost of small DC trackside transformer/rectifiers, how about the high cost of buying a thousand rail borne transformers if DC is scrapped?.
I wonder if people are not taking everything into account in promoting AC conversion. And they would love DC in Goring,although I accept it can't deliver the power needed for 125mph. Although it might if there were less power losses & lighter trains were allowed.

 

[najaB]

Although it might if there were less power losses...

We'll just change the laws of physics then, shall we?

 

[cjmillsnun]

There will of course be more risk to lineworkers, although I think they try to work with the power off unless it's unavoidable for whatever reason. The 8 times as deadly statistic still doesn't seem credible though, unless a hell of a lot of lineworkers are meeting their maker. It'd be intresting to see the methodology behind the statistic.

Add trespassers (or as I call them, idiots) into the mix. On OHLE and non electified, the main issues are not to trip on a rail or on the ballast, and to avoid trains.

However with DC you now have 750V with thousands of amps available and the slightest contact could cause death.

 

[XDM]

No need to change the laws of physics.
Read my post 98. Perhaps 3rd rail power is being lost through current leaking in wet weather to earth due to ballast touching the third rail. It was a polite suggestion,not a challenge to the laws of physics. But maybe even Einstein got an abrasive post when he successfully challenged 200 years of Newtonian physics.
--- old post above --- --- new post below ---
Sorry my post 96.

 

[najaB]

No need to change the laws of physics.
Read my post 98.

Any losses of the type you describe are going to be insignificant as compared to the losses caused by transmitting power at 750 volts v 25kV. Losses due to resistance increase with the square of the current.

 

[XDM]

Exactly. If I am right about wet ballast providing a path back to the power station the loss in DC is enormous ,i squared r. And for 750volts,the current,i,is 25,000 divided by 750 bigger,about 330 times bigger than overhead 25kv..
So it is crucial the third rail is properly insulated. It would be great if an electrical engineer could confirm what I am saying is right, or point out sensibly what is wrong. It seems to me that Network Rail have fallen down on keeping ballast,& footballs,clear of the third rail.

 

[najaB]

Exactly. If I am right about wet ballast providing a path back to the power station the loss in DC is enormous...

Even if you are, I^R is going to result in huge losses, day in - day out, regardless of wet ballast or dry. 750V DC is just not an efficient way to transmit large amounts of power.

 

[Philip Phlopp]

EIt would be great if an electrical engineer could confirm what I am saying is right.

It's all wrong, and you'll upset Bald Rick by suggesting his lot are piling ballast on the third rail.

The losses come from taking 275kV and 400kV from the National Grid and transforming it down to 33kV then taking that, shifting it around our own grid, powering the 33kV to 750V transformers, and then plugging that into third rail, then using EMUs which need an enormous number of watts, that translates into an enormous number of amps being pulled through the third rail.

High amps pulled through the third rail causes resistance and increases the temperature of the third rail, further increasing resistance and requiring further current draw from the transformer to meet the wattage requirements without causing a voltage drop.

25kV AC provides more watts with less amps, current draw is much less, resistance much lower and heating/increasing resistance with current draw far less.

We've done AC and DC loss reports, they're on the NR website. Well worth reading.

 

[Bald Rick]

Why is it claimed 3rd rail track maintenance is costly?

Because you have to switch the damn thing off. It's not as simple as flicking a switch and saying "awight mate, good to go"; there are very careful procedures to make absolutely sure that the correct sections are isolated and protected in the event of an accidental recharge or bridging from a nearby live section. This takes 45-60 minutes to put in place, and another 45 minutes or so to unpick at the end of the job.

Simplifying matters, when there's only 4 hours overnight to do the work, and half of it is taken up sorting out the conductor rail, your productivity is half of that on a non electrified or AC electified line, so it costs twice as much.


--- old post above --- --- new post below ---

A third rail benefit which I omitted to flag up in my last post; DC units don't have to drag 2 tonnes of transformer per 4 cars up hill & down dale.

Except they do. Leaving aside the dual voltage units which obviously do have the transformer, all DC only electrostars have a big lump of concrete in the place where the transformer goes so that the design of suspension etc is standardised with the AC units, and makes future conversion more straightforward. I don't know about the Siemens units but suspect they have something similar.

Besides, 2t of transformer on a 150t unit is a minor issue compared to the power loss in the conductor rail through resistance.

 

[Altnabreac]

We'll just change the laws of physics then, shall we?

Ye cannae change the laws of physics Jim.

 

[Philip Phlopp]

Besides, 2t of transformer on a 150t unit is a minor issue compared to the power loss in the conductor rail through resistance.

I've never actually asked, but what's the total weight of shoe gear and wiring on a 750V DC unit anyway ? It has to add up to something, even if it's not quite 2 tonnes.

 

[najaB]

I've never actually asked, but what's the total weight of shoe gear and wiring on a 750V DC unit anyway ? It has to add up to something, even if it's not quite 2 tonnes.

Given that it has to be beefy to handle the current, I wouldn't be surprised if it was pretty close.

 

[Bald Rick]

I've never actually asked, but what's the total weight of shoe gear and wiring on a 750V DC unit anyway ? It has to add up to something, even if it's not quite 2 tonnes.

I don't know. But then a transformer weighs more than 2 tonnes.

 

[contrex]

The infrastructure has survived for 112 years with very little issue...so again I ask why fix it if it ain't broke? .

Yes I love the sound of all those rotary converter substations whining away, run up and down by their proud attendants, not to mention the quaint old paper insulated cables, the Edwardian transformers and switchgear, the AC side still on 25 cycles. Yet another reason to get out of Europe! Oh and I forgot Durnsford Road power station proudly belching smoke.

Even 90 years ago not everybody favoured 3rd rail. If, at Grouping, the Southern Railway's management structure had not been top-heavy with LSWR men, the picture could have been very different south of the Thames. The LBSCR had already started its 6.7 kV AC overhead system, and the SECR had plans for 3000 V DC (overhead of course!).

 

[najaB]

Yes I love the sound of all those rotary converter substations whining away, run up and down by their proud attendants, not to mention the quaint old paper insulated cables, the Edwardian transformers and switchgear, the AC side still on 25 cycles. Yet another reason to get out of Europe!.

Okay, I've been trying not to bite but I give in - what on Earth does this have to do with Europe?

(Apologies all, I just had to ask.)

 

[Flying_Turtle]

Any losses of the type you describe are going to be insignificant as compared to the losses caused by transmitting power at 750 volts v 25kV. Losses due to resistance increase with the square of the current.

Well... for a flat suburban stretch of double track with roughly 20 miles you may need 6 or 7 substations. For the same stretch with a
25 kv ac feed you only need one and can still feed further 20 to 40 miles of track, depending on the configuration of the network....

 

[thenorthern]

Don't know if anyone has mentioned it but there was talk of electrifying the Marshlink line with 3rd rail but I can't see it happening.

I can't see any more third rail happening though, there hasn't been any major expansion since Weymouth in 1988 and most of the network was installed pre-1956 when British Rail decided the French 25kV AC was the best option. In the 1930s as well I think there was still a large amount of DC generation nearly all of which has ceased now meaning current has to be generated, rectified and then many times inverted again for the train motors which costs a large amount of money.

 

[Flying_Turtle]

Don't know if anyone has mentioned it but there was talk of electrifying the Marshlink line with 3rd rail but I can't see it happening.

I can't see any more third rail happening though, there hasn't been any major expansion since Weymouth in 1988 and most of the network was installed pre-1956 when British Rail decided the French 25kV AC was the best option. In the 1930s as well I think there was still a large amount of DC generation nearly all of which has ceased now meaning current has to be generated, rectified and then many times inverted again for the train motors which costs a large amount of money.

French / Russian / Portuguese / British all in the same boat with a wee hand of zee Germans (which already had their 15 kv 16 2/3 hz (a third of 50 hz) up and running for decades

 

[Gareth]

As posted up-thread by a number of posters, there is a presumption against new 3rd rail installations so the argument is about making the case that 3rd rail will have significant enough advantages over an overhead solution to outweigh its efficiency and safety shortcomings. Infill and short extensions of existing systems likely will, but larger-scale extensions (or new lines) almost certainly won't.

There will be no significant new 3rd rail extensions. No one's suggesting the Midland Main Line be electrified with 750v DC. It also depends on what you consider 'short' extensions. Like all directives, it's open to interpretation. That's quite deliberate and one is supposed to apply common sense when referencing it. I consider the few muted Meseyrail extensions as 'short' for example and so see no need why they can't be 3rd rail, bar extension to Warrington. Some have read the same thing as 'no new third rail whatsoever' though and not only that but also any already extant should be changed over.

 

[WatcherZero]

Okay, I've been trying not to bite but I give in - what on Earth does this have to do with Europe?

(Apologies all, I just had to ask.)

He likes outdated and unsafe technology like paper insulated cables it seems.

 

[AM9]

He likes outdated and unsafe technology like paper insulated cables it seems.

And 3rd rail DC electrification.
--- old post above --- --- new post below ---

There will be no significant new 3rd rail extensions. No one's suggesting the Midland Main Line be electrified with 750v DC. It also depends on what you consider 'short' extensions. Like all directives, it's open to interpretation. That's quite deliberate and one is supposed to apply common sense when referencing it. I consider the few muted Meseyrail extensions as 'short' for example and so see no need why they can't be 3rd rail, bar extension to Warrington. Some have read the same thing as 'no new third rail whatsoever' though and not only that but also any already extant should be changed over.

Probably the last new 3rd rail line was the Surrey Keys to Old Kent Road junction link on the London Overground. It is a short twin track link of about 1.5KM length completely surrounded by ex SR 3rd rail. It is 3KM from any 25kV OLE line (LT&S) on the other side of the River Thames.
I doubt that any stretch of track that isn't 3rd rail at both ends now (apart form sidings) will ever be newly electrified with 3rd rail. If there is any chance of OLE going up near either end it would be delayed or included in the next 25kV scheme.