Benefits of 3rd rail?

[The_Stig]

I was just reading about the Eurostar and how it was transferred to the UK for 3rd rail testing.

I was just wondering if anyone knew of the reasons behind parts of the UK using 3rd rail systems, is there a benefit or is it simply to allow undergound services to operate on the surface?

Any info would be appreciated.

 

[Voyager 2093]

The reason for the Eurostar being transferred to the UK for third rail testing was because it would be using third rail for half the journey from Waterloo - Ashford. But there is no real advantage of third rail but the reason why it is used in certain areas such as LU and on the southern UK lines is because these routes are not very high speed, hence LUL top speed 60mph, so they dont require much power, and third rail doesnt generate much power so it saves the government and TOCs more money to run the line.

 

[43021HST]

For what I know the SR wanted something clean and then revolutionary, Instead of bunging a load of cantenary up and making the place look ugly and full of cables all they did was do some stuff, add a third rail, electrify it. It certainly looks neater than cantenary.

 

[adc82140]

Is there a policy now of not installing any new 3rd rail? Putting down a juice wire to Exeter via Salisbury, on the Oxted line and over the non electrified bits of the North Downs line would certainly put paid to a lot of diesel running, and would I guess be cheaper than putting up OHLE.

 

[generalvegitable]

I know of a good amount of benefits and a few drawback one is speed, the max speed of a 3rd rail train I think is 100mph due to increased friction

 

[me123]

As far as I'm aware, there is to be no new 3rd rail unless your just continuing on from an existing line. This isn't much of a problem; 3rd rail's really restricted to the South East of the country, with notable exceptions in Liverpool and the Glasgow Subway.

Things like the MML and GWML are not permitted to be 3rd rail. Indeed, as "GV" has said, this would result in a decreased speed and longer journey times on these routes.

 

[mrcheek]

Also, I seem to recall reading somewhere that whilst most people would assume 3rd rail is cheaper than over head electrification (one long piece of metal must be cheaper than all those pylons!), it is actually much more expensive, as you need a substation every 2 miles on 3rd rail, instead of every 30 miles on overheads...

 

[Metroland]

3rd rail was out of date around 1907. There was some overhead line installed in 1909 between Victoria and Balham via Crystal Palace on the LBSCR. But the LSWR had gone for 3rd rail, really because it was easier to convert the steam coaches to electric trains in order to go into competition with trams, which were eating into passenger receipts.

Its really an accident of history and down to the LSWR that the southern area has 3rd rail, it very, very nearly was OHL. Indeed the OHL was replaced by the LBSCR in order to follow the LSWR.

 

[merlodlliw]

Also, I seem to recall reading somewhere that whilst most people would assume 3rd rail is cheaper than over head electrification (one long piece of metal must be cheaper than all those pylons!), it is actually much more expensive, as you need a substation every 2 miles on 3rd rail, instead of every 30 miles on overheads...

Correct, the expense killed off 3rd rail Bidston to Wrexham, Network Rail
quoted some colossal amount to electrify the 30 miles or so line.

In the States they ran a 50KV line using only a couple of sub stations over
a big distance, the lower the voltage, the more step ups you need to keep the flow running.

One day 25KV Crewe to Chester for starters. I also recall Altrincham to Manchester was overhead for years,then converted to 25KV, now its
trams.

 

[philjo]

Also the 3rd rail cannot cope with heavy snow/ice.
in the snowfall last February, the rail network in Kent/sussex ground to a halt, whilst the 25kV lines north of London were still running a recognisable service, albeit reduced with some delays.

I remember one trip from Victoria to Canterbury in snow about 15 years ago where there was heavy arcing for the whole trip & max speed was about 30mph. due to limited power available to run the train, heating inside was almost non-existent.

 

[37401]

Just noticed LU was meantioned here, LU is 4th rail not 3rd

 

[tbtc]

the 3rd rail cannot cope with heavy snow/ice

...but it can cope with wind better, as users of the ECML will tell you...

 

[jas_sl]

>The reason for the Eurostar being transferred to the UK for third rail testing was because it would be using third rail for half the journey from Waterloo - Ashford

Am I missing something? I wasn't aware there are any plans for a Waterloo to Ashford Eurostar service. And Eurostar trains don't have a "foot" for a 3rd rail contact, only a pentograph for OHP.

 

[gordonthemoron]

When E* was first introduced, and prior to HS1, it used 3rd rail from Waterloo International to Cheriton

 

[jopsuk]

Am I missing something? I wasn't aware there are any plans for a Waterloo to Ashford Eurostar service. And Eurostar trains don't have a "foot" for a 3rd rail contact, only a pentograph for OHP.

You're missing a heck of a lot! Until late 2007, all Eurostars ran into Waterloo through south London. Untill 2003, they ran on local lines all the way from the tunnel to London. They were built with third rail pickups for this very purpose. I'm guessing they've now had the shoes removed though, as the gear is redundant.

 

[CosherB]

I also recall Altrincham to Manchester was overhead for years,then converted to 25KV, now its
trams.

I used to go to school on the Altrincham electrics. They were 1,500V DC overhead, and about 2,000hp for a 6-coach train, so quite lively - much more so than the underpowered 25KV AC units that replaced them when the Crewe-Manchester electrification was extended to Altrincham (so the line has run as non-electric, 1,500V DC, 25KV AC, and now 600V DC for the trams).

As you say, the line has now gone and is a tramway. I always thought it a great shame that we lost that 25KV south Manchester commuter line to the trams - it should have been extended to Chester and would have provided a useful link to the WCML at Hartford and encourage the extension of the Manchester Airport stub through the airport to join the Chester line for a northern link to the WCML. But that's all lost now! 6 coach DC electric trains replaced initially by 3-coach AC electrics, then by trams comprising 2 short units! No wonder they are overcrowded!

 

[SouthEastern-465]

Origanally the LBSCR used a overhead system,but after the grouping of 1923,the SR choose the 3RD rail as It was cheaper,and less problamatical,and this was aided by the fact that the LSWR had electrified more of Its lines then Its neighbour the LBSCR.

Hope this helped "The Stig"
Regards

 

[D1001]

You're missing a heck of a lot! Until late 2007, all Eurostars ran into Waterloo through south London. Untill 2003, they ran on local lines all the way from the tunnel to London. They were built with third rail pickups for this very purpose. I'm guessing they've now had the shoes removed though, as the gear is redundant.

I would guess they have been retained in case of diversions, maybe?

 

[merlodlliw]

I used to go to school on the Altrincham electrics. They were 1,500V DC overhead, and about 2,000hp for a 6-coach train, so quite lively - much more so than the underpowered 25KV AC units that replaced them when the Crewe-Manchester electrification was extended to Altrincham (so the line has run as non-electric, 1,500V DC, 25KV AC, and now 600V DC for the trams).

As you say, the line has now gone and is a tramway. I always thought it a great shame that we lost that 25KV south Manchester commuter line to the trams - it should have been extended to Chester and would have provided a useful link to the WCML at Hartford and encourage the extension of the Manchester Airport stub through the airport to join the Chester line for a northern link to the WCML. But that's all lost now! 6 coach DC electric trains replaced initially by 3-coach AC electrics, then by trams comprising 2 short units! No wonder they are overcrowded!

Fully agree with you Captain, and thanks for the history, I recall seeing
the overheads running when I used to go to Belle Vue for judo training
in the 1950s on Sunday afternoons,in the winter by car from Rhyl.

 

[GB]

...but it can cope with wind better, as users of the ECML will tell you...

High winds rarely bring down the lines. However they are alot more susceptible to heat and dodgy pantographs.

 

[jopsuk]

I would guess they have been retained in case of diversions, maybe?

Dunno, Waterloo International is fully shut, even the escalators from the main station to check in have been taken away.

 

[Phoenix]

High winds rarely bring down the lines. However they are alot more susceptible to heat and dodgy pantographs.

You will probably know is Heat the main reason behind the GEML OHLE failures because I recently heard a lot of the incidents were due to the wires sagging due to the poor tensioning between chelmsford and Liv street.

 

[GB]

You will probably know is Heat the main reason behind the GEML OHLE failures because I recently heard a lot of the incidents were due to the wires sagging due to the poor tensioning between chelmsford and Liv street.

Quite simply yes. The OHLE in the Chelmsford and Ingatestone area is of very old design and doesnt have tension weights like other areas. So there is nothing to counter-act the sagging during the very hot periods.

Having said that, thats not to say that a dodgy pantograph hasn't contributed to any of the incidents, but its generally put down to the sagging wires.

 

[O L Leigh]

The problem with OLE and wind is not that the wind blows the wires down, but that it often blows something over that in turn brings the wires down (e.g. a tree). There can be problems with excessive sway as a consequence of high wind that can result in a speed restriction if the wires are likely to go too far outside of the stagger pattern, but this is because there is a risk that the wire will run off the end of a pan and cause a dewirement.

The GEML OLE at the southern end doesn't have a problem with poor tensioning. The problem is that the original 1949 LNER design had no tensioning. When the wires lengthened in the heat the slack was not taken up, which meant that there was again a risk of excessive sway and a dewirement if the wire ran off the end of a pan. However, the OLE is being modified as part of a rolling programme to provide tensioning. The stretch from Liverpool St to Stratford at least has been completed.

However, to drag this back on-topic, I would have to say that on balance the OLE is a superior system. It gets some stick for being a bit of an eyesore and vulnerable in certain weather conditions, but these are criticisms that could be addressed if there was a budget sufficient to cover the additional costs. Unfortunately the 3rd rail will always be susceptible to both icing and flooding.

O L Leigh

 

[Bighat]

I used to go to school on the Altrincham electrics. They were 1,500V DC overhead, and about 2,000hp for a 6-coach train, so quite lively - much more so than the underpowered 25KV AC units that replaced them when the Crewe-Manchester electrification was extended to Altrincham (so the line has run as non-electric, 1,500V DC, 25KV AC, and now 600V DC for the trams).

As you say, the line has now gone and is a tramway. I always thought it a great shame that we lost that 25KV south Manchester commuter line to the trams - it should have been extended to Chester and would have provided a useful link to the WCML at Hartford and encourage the extension of the Manchester Airport stub through the airport to join the Chester line for a northern link to the WCML. But that's all lost now! 6 coach DC electric trains replaced initially by 3-coach AC electrics, then by trams comprising 2 short units! No wonder they are overcrowded!

Were they the eight 3 car sets built to the same specification as the 92 3 car sets built in 1949 to polulate the newly electrified Liverpool Street-Shenfield service in London?
--- old post above --- --- new post below ---

The problem with OLE and wind is not that the wind blows the wires down, but that it often blows something over that in turn brings the wires down (e.g. a tree). There can be problems with excessive sway as a consequence of high wind that can result in a speed restriction if the wires are likely to go too far outside of the stagger pattern, but this is because there is a risk that the wire will run off the end of a pan and cause a dewirement.

The GEML OLE at the southern end doesn't have a problem with poor tensioning. The problem is that the original 1949 LNER design had no tensioning. When the wires lengthened in the heat the slack was not taken up, which meant that there was again a risk of excessive sway and a dewirement if the wire ran off the end of a pan. However, the OLE is being modified as part of a rolling programme to provide tensioning. The stretch from Liverpool St to Stratford at least has been completed.

However, to drag this back on-topic, I would have to say that on balance the OLE is a superior system. It gets some stick for being a bit of an eyesore and vulnerable in certain weather conditions, but these are criticisms that could be addressed if there was a budget sufficient to cover the additional costs. Unfortunately the 3rd rail will always be susceptible to both icing and flooding.

O L Leigh

Yes, I remember the 1949 wiring, but that was for 1500v dc IIRC. During the late 1950's, when the lines were electrified to Southend Victoria and beyond and the LTSR, the system (and the 92 3-cars sets) were converted to 25,000v AC, and IIRC much rewiring (and tensioning?) was also done. Again IIRC, in the 'inner sections' wasn't the voltage reduced to 7.250v AC due to low clearances?

 

[O L Leigh]

The electrification from Liv St to Chelmsford and Southend Victoria was indeed originally energised at 1500V DC and was later converted to AC. The original voltage for the AC system was just 6.25kV because of low clearances under bridges, but testing soon showed that the system could be energised at 25kV without the need to alter the clearances and, by 1980, the entire GEML electrification was energised at this voltage.

However, I don't believe that there were any modifications to the OLE itself because the changeover from 1500V DC to 6.25kV AC happened over the course of a weekend. One supply was turned off and then the other was turned on. Likewise the work to uprate the supply to 25kV AC was centred mostly on the power supply end rather than the OLE. However, this later change took approximately 4 years. But then almost all GE EMU's in service at that time could work from either the 6.25kV AC system or the 25kV AC system, so the work could be staged without affecting train operations. In spite of these various power upgrades, the original 1949 GEML OLE was never altered to include tensioners. It is only now, 60 years later, that this oversight is being corrected.

O L Leigh

 

[The_Stig]

>The reason for the Eurostar being transferred to the UK for third rail testing was because it would be using third rail for half the journey from Waterloo - Ashford

Am I missing something? I wasn't aware there are any plans for a Waterloo to Ashford Eurostar service. And Eurostar trains don't have a "foot" for a 3rd rail contact, only a pentograph for OHP.

I was just wanting to know peoples views on the 3rd rail vs OHLE, I have to say that the people on here are quite knowledgeable and have put forward things I had not considered.

I am only privy to the 3rd rail on the Glasgow subway, where it simply makes more sense than running over-head lines and was simply curious.

It was not meant as a joke or whatever you may have thought it was.

 

[Aictos]

I don't mind the 3rd rail so much seeing as I live and work on the ECML, still I like hearing the humm of the trains picking up power be it 313s on the NCL or 319s on the Thameslink,

Still they both have their ups and downs, I'm for the more practical type where electrification projects are concerned.

 

[coral reef]

Eurostars have had their shoes removed. IIRC they weren't like normal shoes, that are normally just pads fixed to a plank, they were 4 little feet per end power car that actually descended from an up position. I assume the complexity of such an arrangement meant that they were more of a risk to operations, and removal justified.

 

[EWS 58038]

The only benefit of 3rd rail is for photographers...