Possible third rail electrifications

[Philip Phlopp]

If you can get those statistics,& their provenance& their assumptions it would enable everyone to draw sensible conclusions, anything else is no better than coronation street gossip. The Oxford dictionary is the only one used by the BBC I was told by a friend a few years ago. All queries about right usage are judged by the Duty Editor (their fat controller) byreference to the concise Oxford dictionary. And if any outfit is accepted as official it is the BBC. QED.

The public data is the RSSB SMIS data, which you can pull from the RSSB website, it covers fatalities and electric shock incidents to staff and public. 2014/15 data is, I believe, 1 fatality and 2 serious injuries on DC, 2 serious injuries on AC, and 4 serious injuries from diesel-electric traction electric.

The risk is then calculated by working out electrified route mileage to calculate the risk score for third rail v OLE on a per mile basis, with some complex risk scoring metric system, which gives AC a score of 1 (baseline) and DC a score of 8.

 

[najaB]

The public data is the RSSB SMIS data, which you can pull from the RSSB website...

Thanks for this - the 14/15 full report lists fatalities in Appendix 2. The electrification-related fatalities are:

07/04/2014, Horley, South East, Platform/train interface
On 7 April 2014, a teenage boy fell from the platform edge and was electrocuted after coming into contact with the conductor rail. Alcohol was reported as a potential factor in the incident.

24/05/2014, St Leonards West Marina Depot, South East, Electric shock
On 24 May 2014, a train cleaner, working in a depot, was electrocuted after coming into contact with the live rail, after an apparent fall.

So two fatalities on 'safe' third-rail and none on 'dangerous' OHLE.

 

[AM9]

The public data is the RSSB SMIS data, which you can pull from the RSSB website, it covers fatalities and electric shock incidents to staff and public. 2014/15 data is, I believe, 1 fatality and 2 serious injuries on DC, 2 serious injuries on AC, and 4 serious injuries from diesel-electric traction electric.

The risk is then calculated by working out electrified route mileage to calculate the risk score for third rail v OLE on a per mile basis, with some complex risk scoring metric system, which gives AC a score of 1 (baseline) and DC a score of 8.

Whenever I have encountered risk factoring it is based on a matrix plotting probability against severity. In each of the intersections was a number that when set against the rules, determined whether the risk was acceptably low to live with, to require mitigation or in extreme cases, force a change of design/practice or even prohibition.
I would imagine that DC carried a slightly lower risk of severity owing to the possibility of a brush against a conductor where the momentary current did not cause muscles to maintain contact, whereas a similar contact with a 25kV ac conductor would cause a much larger energy level, more likely to result in electrocution. On the other axis though, the probability of being near enough to touch an OLE system's live conductor would be far less likely than contact with a 3rd rail component especially with the amount of PW work undertaked on live track.

 

[snowball]

The official UK dictionary,the concise Oxford dictionary,

As others have said there is no "official UK dictionary". The Concise Oxford Dictionary is a relatively small dictionary, much smaller than the Shorter Oxford English Dictionary, which in turn is much smaller than the Oxford English Dictionary (OED). The OED is usually regarded as the most authoritative dictionary.

If you're a member of a UK public library you probably have online access to the OED. This is what it says:

orig. U.S.

1. trans. To put to death by means of a powerful electric current; to execute in the electric chair.

1889 Trenton (New Jersey) Times 7 June 4/2 (heading) He wants to be ‘electrocuted’... An offer on the part of a man..to act as a victim..by testing the..new apparatus for executing by electricity.
1890 Congress. Rec. 8375/1 That the gentleman..should be ‘electrocuted’ by the Kemmler process recently adopted in the state of New York.
1903 W. D. Howells Lett. Home v 32, I could be sitting this moment with the transmitter at my mouth, and the receivers strapped to both ears, and looking as if I were just going to be electrocuted.
1945 N. Mitford Pursuit of Love xiii. 101, I bet the Scotsboro' boys will be electrocuted in the end, if they don't die of old age first, that is.
2001 Times (Nexis) 28 July In Georgia I stood outside death row as the state electrocuted a man I thought was probably innocent.


2. trans. To give an electric shock to; esp. (chiefly refl. or in pass.) to kill or injure by electric shock.

1890 Freeborn County Standard (Albert Lea, Minnesota) (Electronic text) 24 Sept. When venture-some rodents walk within a metallic cage, containing cheese, they are transfixed by a strong electric current and ‘electrocuted’.
1899 Times 11 Apr. 1/4 Continuation of the Monster Holiday Show. Marvellous performances... See to-day, at 3 and 8, Dr. Walford Bodie electrocute a man.
1909 Yorks. Post 4 Aug. 4/5 [A boy] who was electrocuted on the Mersey Railway last Saturday.
1939 D. L. Sayers In Teeth of Evid. 9 One of them got loose last time and tried to electrocute itself on the X-ray plant.
1988 Courier-Mail (Brisbane) (Nexis) 10 May I was electrocuted. I can still smell the flesh burning.
2004 Chicago Tribune (Midwest ed.) 11 July x. 23/2, I wasn't going to touch a battery—I'd have electrocuted myself.

 

[edwin_m]

Whenever I have encountered risk factoring it is based on a matrix plotting probability against severity. In each of the intersections was a number that when set against the rules, determined whether the risk was acceptably low to live with, to require mitigation or in extreme cases, force a change of design/practice or even prohibition.
I would imagine that DC carried a slightly lower risk of severity owing to the possibility of a brush against a conductor where the momentary current did not cause muscles to maintain contact, whereas a similar contact with a 25kV ac conductor would cause a much larger energy level, more likely to result in electrocution. On the other axis though, the probability of being near enough to touch an OLE system's live conductor would be far less likely than contact with a 3rd rail component especially with the amount of PW work undertaked on live track.

This happens on the railway too when doing risk assessments for new infrastructure and activities. The risk matrix is probably too coarse to distinguish the difference in fatality rates between 25kV and 750V electric shocks (people have survived both but I don't know how the probability of survival differs). I suspect in building the risk model RSSB will have done more detailed analysis taking account of all the accident data going back several years, but unfortunately I can't find any of this supporting information in the public domain or on the login-only portion of the RSSB website (RSSB member organisations have wider access though).

However the ORR policy document states that they consider the risk of third rail is only tolerable if it is "grossly disproportionate" to use anything else. Hence the presumption against even extensions of existing third rail unless the proposer can demonstrate there is no real alternative available.

 

[SpacePhoenix]

3rd rail is probably more risky as there's plenty of chance for someone to accidentally come into contact with it. With overhead someone would have to deliberately go near it to get electrocuted

 

[najaB]

3rd rail is probably more risky as there's plenty of chance for someone to accidentally come into contact with it. With overhead someone would have to deliberately go near it to get electrocuted

Common sense would suggest that is the case, however for some reason XDM and company don't seem to agree.

 

[GRALISTAIR]

3rd rail is probably more risky as there's plenty of chance for someone to accidentally come into contact with it. With overhead someone would have to deliberately go near it to get electrocuted

Common sense would suggest that is the case, however for some reason XDM and company don't seem to agree.

Sadly it does appear that way to a casual observer.

 

[Andyjs247]

3rd rail is probably more risky as there's plenty of chance for someone to accidentally come into contact with it. With overhead someone would have to deliberately go near it to get electrocuted

Quite! People don't generally fall onto overhead wires whereas a fall from a platform could quite conceivably bring someone into contact with the 3rd rail!

Times change. Standards change. Safety has improved. The regulators are not going to allow more 3rd rail as legislation pretty much prevents it. According to eg the Electricity at Work Regulations, live conductors either have to be covered with insulation or placed out of reach. Systems have to be designed to prevent danger as far as is possible, or words to that effect.

What was once accepted is no longer possible. Not only that it's technically inferior. More 3rd rail is just not going to happen. About the only thing in its favour is that it looks nicer.

 

[GRALISTAIR]

More 3rd rail is just not going to happen. About the only thing in its favour is that it looks nicer.

Yes - without wishing to get too far OT=the Goring Gap crowd would love it unless of course one of their dogs got electrocuted

 

[Philip Phlopp]

3rd rail is probably more risky as there's plenty of chance for someone to accidentally come into contact with it. With overhead someone would have to deliberately go near it to get electrocuted

And we've just increased the difficulty in approaching 25kV OLE by increasing bridge parapet height to 1.8m from 1.5m.

Series 1 where fitted reduces the 'energised' area which also makes the system safer for staff and the general public, just moving the energised components further away from platforms and things like umbrellas.

 

[SodTheDrummer]

About the only thing in its favour is that it looks nicer.

I like the look of the Series 1 kit actually - it has a sort of industrial elegance to it...

 

[Tio Terry]

And we've just increased the difficulty in approaching 25kV OLE by increasing bridge parapet height to 1.8m from 1.5m.

Series 1 where fitted reduces the 'energised' area which also makes the system safer for staff and the general public, just moving the energised components further away from platforms and things like umbrellas.

The increase in parapet height is driven by the requirements of the Technical Standard for Interoperability - Energy. This specifies 1.8M

The Energised Component that comes closest to members of the public is invariably the end of the pantograph, don't think Series 1 affects this.

 

[Philip Phlopp]

The increase in parapet height is driven by the requirements of the Technical Standard for Interoperability - Energy. This specifies 1.8M

The Energised Component that comes closest to members of the public is invariably the end of the pantograph, don't think Series 1 affects this.

The Series 1 (single) insulator placement leaves around half the cantilever arm assembly (by length) insulated, whereas Mark 1 and Mark 3 has the insulator assembly between mast and cantilever arm, so the entire cantilever assembly is energised.

Pantograph horns really only are relevant when working out safe distances for platform passengers, but yes, they're probably the closest energised (and unprotected) part to most passengers.

 

[Taunton]

I see the DLR is looking at extensions again. Why will they be allowed to get away without installing overhead?

You also have to wonder why the DLR, which only started service in the late 1980s and had no structural clearance issues like low tunnels, went for 3rd rail rather than overhead in the first place, given the huge advantages all above have stated. Were the DLR design engineers a load of know-nothings?

 

[SpacePhoenix]

I see the DLR is looking at extensions again. Why will they be allowed to get away without installing overhead?

You also have to wonder why the DLR, which only started service in the late 1980s and had no structural clearance issues like low tunnels, went for 3rd rail rather than overhead in the first place, given the huge advantages all above have stated. Were the DLR design engineers a load of know-nothings?

http://www.alamy.com/stock-photo-ba...on-platform-bank-city-of-london-68686407.html

Looking at that picture there I'd be surprised if you could even squeeze an overhead rail system in, let alone catenary

 

[Domh245]

I see the DLR is looking at extensions again. Why will they be allowed to get away without installing overhead?

You also have to wonder why the DLR, which only started service in the late 1980s and had no structural clearance issues like low tunnels, went for 3rd rail rather than overhead in the first place, given the huge advantages all above have stated. Were the DLR design engineers a load of know-nothings?

750DC is the preferred choice for metro systems. Off the top of my head, I can't remember why, but if I had to guess, it may well be to do with the need to not carry a transformer around with them. Lightweight vehicles are key to a metro system as they can then accelerate and decelerate quicker.

As to why the DLR gets away with third rail, I would guess that it is because the DLR has a bottom contact third rail, which is far safer than a top contact one. In order to come into contact with the live part of the rail, you have to go out of your way to touch it, which is contrary to 'conventional' third rail where you can come into contact with it unintentionally. That and the fact that the rest of the system is third rail and they don't have any dual voltage stock.

 

[A0]

I see the DLR is looking at extensions again. Why will they be allowed to get away without installing overhead?

You also have to wonder why the DLR, which only started service in the late 1980s and had no structural clearance issues like low tunnels, went for 3rd rail rather than overhead in the first place, given the huge advantages all above have stated. Were the DLR design engineers a load of know-nothings?

If you look at some of the books on the DLR you'll see some of the original ideas assumed it would be OHLE albeit of the more 'lightweight' type used by tram / metro systems rather than a full heavy rail type.

I believe the London Docklands Dev Corp didn't want overhead wires as they felt it was not aesthetically pleasing - given the electrification of the DLR was always going to be a 750v DC, it did mean changing to a 3rd rail arrangement was viable (which if it had been planned as 1.5kv DC or 25kv AC wouldn't have been possible). Had the DLR involved any 'street' running (as Manchester Metrolink did) you can guarantee it would have had to use OHL.

However the DLR did go for a 'safer' version of 3rd rail by adopting a bottom contact approach which means the conductor rail is shielded.

As others have pointed out, it contributes to keeping the weight of the vehicles down - and DLR speeds are relatively low (max 50mph) - quite unlike the mainline network.

In terms of extensions - I believe (someone else will confirm) that 3rd rail extensions on such systems are permitted (as indeed are extensions to the 4th rail system on London Underground) - in part because clearances and tunnel running and in part because these are contained systems.

 

[najaB]

However the DLR did go for a 'safer' version of 3rd rail by adopting a bottom contact approach which means the conductor rail is shielded.

That, more than anything, is why they will be allowed to extend their network. The danger doesn't come from 3rd rail, it comes with exposed third rail.

 

[edwin_m]

As well as the bottom contact third rail, DLR and most modern metros have safety procedures which don't allow their staff to go near the track when the power is on or trains are running. This is much more difficult on the main line, not least because many routes don't have a convenient shutdown every night when maintenance can take place. The fencing on DLR is probably better than on the main line too, not least because a lot of it is on a viaduct...

Most early electrification systems supplied trains and trams at a voltage between 600 and 750 volts, because that was the maximum voltage that could be fed to the traction motors available at the time, and nor was there any practical or economical means of reducing the voltage on board a train (substations at the time had rotary converters and were as big as large houses).

A few recent metros have upped the third rail voltage to 1500V, as this reduces power losses without having to have a transformer on each train or enlarge structures and tunnels for an overhead line.

 

[mr_jrt]

...because the DLR as-built was a glorified tram running over such short distances that the number of substations wasn't really too great a factor and the bottom contact improved the safety case?

 

[edwin_m]

...because the DLR as-built was a glorified tram running over such short distances that the number of substations wasn't really too great a factor and the bottom contact improved the safety case?

Or to put it another way, lower voltage DC is better for short distance services with frequent stops, and high voltage AC is better for long distances and mixed traffic. But ideally you want the main line network to have the same electrification system throughout, for which 25kV is the obvious choice. Not just NR, several railways across Europe that previously had DC electrification at various voltages have done new electrification at 25kV and some are even converting existing DC to that voltage.

 

[apk55]

The maximum power that 3rd rail can provide is about 4MW with substations less than 2 miles apart. On most sections the maximum power is more like 2MW. This rules out heavy high speed trains (look at the performance of Eurostar trains on DC).

There is also a problem with locomotive hauled trains both due to gapping and just picking up current due to the short length of a loco. This makes electrically hauled freight unattractive and if power is limited to 2MW then performance would less than less tan a class 66.

On AC lines point loads of 8MW are common (eg pendelino or double headed freight) and most parts of the system could cope with 4MW loads.

 

[po8crg]

Or to put it another way, lower voltage DC is better for short distance services with frequent stops, and high voltage AC is better for long distances and mixed traffic.

The voltage doesn't have much to do with the delivery system; you can use DC on overhead - tram systems are 750V DC in the UK, and Newcastle Metro is 1500V DC. The reverse isn't true; you can't have 25kV AC on third rail.

There are safer ways than conventional third-rail of delivering 750V DC to a light vehicle when aesthetics or infrastructure constraints prevent third rail (note that this is not true for a heavy, fast train, like the 801s in the Goring Gap, as that requires high-voltage AC). You can use a ground-level supply and automatically energise segments only when under the tram (like the APS system in Bordeaux). You can also use side or bottom contact third-rail. If it's just a small section without wires, like in Nice or Birmingham, then a battery is also an option.

If it really isn't practical to move Merseyrail tunnels to OHLE - and, given that there have been doubts expressed over whether a non-PEP roof profile would fit even without a pantograph and wires on top, then I can see there could be a problem - then it might be sensible at the next renewal to move the rest of Merseyrail to OHLE and put in bottom-contact in the tunnels. At least there would be DLR to ensure that spares would be available for the bottom-contact and it wouldn't be a unique system.

The OHLE might even be 750V DC; Merseyrail is an essentially isolated system, and runs relatively light vehicles, which could benefit from not having to carry a transformer. However, there are some issues, most notably Chester station - where isolating Merseyrail DC from any future mainline AC is apparently giving the designers hives, and will constrain platform usage; switching Merseyrail to OHLE DC won't actually help, but once you've put any part of Merseyrail under 25kV AC, you have to have the dual-voltage ability on your trains, so you might as well make all the OHLE 25kV.

 

[edwin_m]

If it really isn't practical to move Merseyrail tunnels to OHLE - and, given that there have been doubts expressed over whether a non-PEP roof profile would fit even without a pantograph and wires on top, then I can see there could be a problem - then it might be sensible at the next renewal to move the rest of Merseyrail to OHLE and put in bottom-contact in the tunnels. At least there would be DLR to ensure that spares would be available for the bottom-contact and it wouldn't be a unique system.

The OHLE might even be 750V DC; Merseyrail is an essentially isolated system, and runs relatively light vehicles, which could benefit from not having to carry a transformer. However, there are some issues, most notably Chester station - where isolating Merseyrail DC from any future mainline AC is apparently giving the designers hives, and will constrain platform usage; switching Merseyrail to OHLE DC won't actually help, but once you've put any part of Merseyrail under 25kV AC, you have to have the dual-voltage ability on your trains, so you might as well make all the OHLE 25kV.

I don't think the top-contact third rail is a major concern in the Merseyrail tunnels, as the tight clearances mean trains can't be running when staff are on the track, and if it isn't done already it should be possible to ensure the power is off too. Any trespassers are likely to be obliterated by a train regardless of how it is powered. Bottom contact is however possible and I don't think there'd be an issue with continued availability of components considering that many other metros use something very similar. However the bottom contact pickups would project outside the standard loading gauge so some clearances might need improving elsewhere on the network.

I was trying to work out whether Merseyrail could work with separate DC-only and dual-voltage sub-fleets and I don't think it would. As well as Chester, Merseyrail interfaces with 25kV at Hunts Cross and might also do so at Southport and somewhere on the Kirkby-Wigan and Burscough-Preston sections. If all these happen then nearly all of the diagrams would use at least one section where voltage conversion is possible within the lifetime of the new trains.

 

[A0]

There are safer ways than conventional third-rail of delivering 750V DC to a light vehicle when aesthetics or infrastructure constraints prevent third rail (note that this is not true for a heavy, fast train, like the 801s in the Goring Gap, as that requires high-voltage AC). You can use a ground-level supply and automatically energise segments only when under the tram (like the APS system in Bordeaux). You can also use side or bottom contact third-rail. If it's just a small section without wires, like in Nice or Birmingham, then a battery is also an option.

If it really isn't practical to move Merseyrail tunnels to OHLE - and, given that there have been doubts expressed over whether a non-PEP roof profile would fit even without a pantograph and wires on top, then I can see there could be a problem - then it might be sensible at the next renewal to move the rest of Merseyrail to OHLE and put in bottom-contact in the tunnels. At least there would be DLR to ensure that spares would be available for the bottom-contact and it wouldn't be a unique system.

The OHLE might even be 750V DC; Merseyrail is an essentially isolated system, and runs relatively light vehicles, which could benefit from not having to carry a transformer. However, there are some issues, most notably Chester station - where isolating Merseyrail DC from any future mainline AC is apparently giving the designers hives, and will constrain platform usage; switching Merseyrail to OHLE DC won't actually help, but once you've put any part of Merseyrail under 25kV AC, you have to have the dual-voltage ability on your trains, so you might as well make all the OHLE 25kV.

I think in tunnel sections there is less concern about the use of 3rd rail, not least because the risk of trespass onto the track is much reduced.

Oddly enough, there has been 750v DC overhead in the past - in fact the class 71s were built with pantographs to allow collection from such systems which it was envisaged would be used in yards where the risks of staff coming into contact with 3rd rail were greater.

I'm not sure there's much point in changing the national network's contact system on 3rd rail, particularly if over time most of the old Southern Region is re-electrified on OHLE - which we already know is likely to happen for bits of the SWML and I'd expect the Brighton mainline and Kent Coast to be looked at particularly when DC equipment needs replacement.

 

[Philip Phlopp]

I think in tunnel sections there is less concern about the use of 3rd rail, not least because the risk of trespass onto the track is much reduced.

Oddly enough, there has been 750v DC overhead in the past - in fact the class 71s were built with pantographs to allow collection from such systems which it was envisaged would be used in yards where the risks of staff coming into contact with 3rd rail were greater.

I'm not sure there's much point in changing the national network's contact system on 3rd rail, particularly if over time most of the old Southern Region is re-electrified on OHLE - which we already know is likely to happen for bits of the SWML and I'd expect the Brighton mainline and Kent Coast to be looked at particularly when DC equipment needs replacement.

Third rail to OLE replacement isn't proposed to be done purely for safety purposes specifically, it's for most points, a secondary consideration and benefit. You would be replacing third rail with OLE to cut energy consumption, make signalling more reliable, and to make track replacement much easier.

Those benefits aren't so significant and pronounced on the MerseyRail network, where maintenance is already more complex and energy losses much lower currently thanks to the nature/topography of the network.

 

[Mordac]

The voltage doesn't have much to do with the delivery system; you can use DC on overhead - tram systems are 750V DC in the UK, and Newcastle Metro is 1500V DC. The reverse isn't true; you can't have 25kV AC on third rail.

There are safer ways than conventional third-rail of delivering 750V DC to a light vehicle when aesthetics or infrastructure constraints prevent third rail (note that this is not true for a heavy, fast train, like the 801s in the Goring Gap, as that requires high-voltage AC). You can use a ground-level supply and automatically energise segments only when under the tram (like the APS system in Bordeaux). You can also use side or bottom contact third-rail. If it's just a small section without wires, like in Nice or Birmingham, then a battery is also an option.

If it really isn't practical to move Merseyrail tunnels to OHLE - and, given that there have been doubts expressed over whether a non-PEP roof profile would fit even without a pantograph and wires on top, then I can see there could be a problem - then it might be sensible at the next renewal to move the rest of Merseyrail to OHLE and put in bottom-contact in the tunnels. At least there would be DLR to ensure that spares would be available for the bottom-contact and it wouldn't be a unique system.

The OHLE might even be 750V DC; Merseyrail is an essentially isolated system, and runs relatively light vehicles, which could benefit from not having to carry a transformer. However, there are some issues, most notably Chester station - where isolating Merseyrail DC from any future mainline AC is apparently giving the designers hives, and will constrain platform usage; switching Merseyrail to OHLE DC won't actually help, but once you've put any part of Merseyrail under 25kV AC, you have to have the dual-voltage ability on your trains, so you might as well make all the OHLE 25kV.

Someone in the know might want to confirm, but I'm fairly sure I've read that the specification for the current Merseyrail stock tender requires the new trains to be dual mode.

 

[Philip Phlopp]

Someone in the know might want to confirm, but I'm fairly sure I've read that the specification for the current Merseyrail stock tender requires the new trains to be dual mode.

It does - be useful for the North Wales Coast and an extension of some services to Shotton and Flint (though I was called a lying ******* when I suggested this was looked at as part of the business case for the North Wales Coast electrification).

 

[Holly]

Third rail to OLE replacement isn't proposed to be done purely for safety purposes specifically, it's for most points, a secondary consideration and benefit. You would be replacing third rail with OLE to cut energy consumption, make signalling more reliable, and to make track replacement much easier.
Those benefits aren't so significant and pronounced on the MerseyRail network, where maintenance is already more complex and energy losses much lower currently thanks to the nature/topography of the network.

There would be a good case to making Chester-Hooton 25kV OHLE when mainline electrification comes to Chester Station.