How Trains Are Powered on the Railway | Third Rail vs Over Head Line Wires
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- เผยแพร่เมื่อ 9 ก.ค. 2024
- 🚆 As we transition away from carbon-based fossil fuels, public transport is in the spotlight, especially railways. Electric trains are key to reducing our carbon footprint, but how is electricity delivered to these trains? This video dives into the two main systems: overhead lines and third rail systems. ⚡️
Explore the pros and cons of each system, and understand why one might be chosen over the other. But is electrification always the best choice? Stay tuned till the end to find out!
🛤️ Learn about the origins of these systems, their advantages, and the significant drawbacks. From cost and maintenance to safety and efficiency, we cover it all.
#RailwayElectrification #OverheadLines #ThirdRail #ElectricTrains #RailwayEngineering #PublicTransport #Decarbonization #TrainSafety #RailwayInfrastructure #SustainableTransport
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Video Chapter's:
00:00 - Intro
01:01 - Third rail
04:15 - Overhead line
08:19 - The move to electrification
09:32 - Summary - วิทยาศาสตร์และเทคโนโลยี
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My father in-law was working on an overhead gantry, he slipped and came into contact with the 1500VDC used on Australian suburban trains, he survived but lost his arm just past his elbow. (boy was he lucky)
As for wires stretching during heat events, that has long been solved by using weights and pulley wheels to keep a constant tension on the lines, irrespective of the heat, have a look at 0:20 those 'things' ever side of the poles are a stack of steel plates used for such.
Would that be in Sydney or Melbourne? As they both use 1,000VDC! Not like in Brisbane they use 25,000V~
@@jonathonshanecrawford1840 Well that's interesting for what I know Melbourne is 1500, and I assumed the rest of Australia would be the same.
I think you have got which units need transformers mixed up. For example, the British Rail Class 86 locos have transformers to reduce voltage from 25kv to 900v for the motors, whereas British Rail Class 423 4VEPs don't have a transformers for traction power as they get the 750v direct from the third rail. DC units without transformers require ballast to keep their centre of gravity low. British Rail Class 86s are 25kv AC OLE locos, and the British Rail Class 423 4VEPs are 750v DC third Rail units.
Thank you for the information!
Second that… 😅 Transformers only work with AC, as the fluctuating polarity is needed to create the shifting magnetic field induction to the secondary coil(s). Running DC through one would just create a big magnet - and a single spike across the secondary coil (and an opposite polarity spike when turned off).
Early AC traction was regulated by tapping into sections of the coils, mostly avoiding huge and hot resistors used with DC (energy loss). Mercury or motor rectifiers were often used in AC, as DC drive-motors were more efficient than AC ones.
Last 50ish years, both AC and DC fed traction is either “chopped” (like a lamp dimmer, but huge), or turned into multiphase variable frequency - a bit like e-vehicles. All solid state without moving mechanics - except the driving motor-wheel assembly.
Oh well, this was certainly more than anyone asked for… (and correct me if & where wrong) 😅
DC units do not require ballast- their CoG is already low and quite irrelevant. Diesel locos have a higher CoG due to the mass of their engine & generator.
@@MervynPartin Agree - I overlooked the “ballast” part, as this video was about electric traction… Silly me. 😅
@@MervynPartin afaik, ballast can be used, but it’s because the electric equipment is too light and wouldn’t get the full axle load for maximum usable traction (mostly a concern for low speed drags and thus cargo only operations in countries like the US with few limits on train length and minimum train speeds)
It's pretty cool to ride on a train in the dark depths of Finnish winter and see the trackside illuminated in the flickering blue glow as the pantograph constantly makes and breaks contact through the ice.
Waiting to see what they do with the Forth Bridge, whether they're going to put masts on it or run trains on battery.
It will be interesting to see! Maybe more steel work to be painted!
i'd go with some small (1km range) batteries that can be recharged from the overhead very quickly.
@@philhoward4466 The Forth Bridge is 2.5km long...
Rapid wear to the pantograph
One of the disadvantages of OLE you mentioned was sagging lines. Most (if not all) lines have "automatic" tensioners installed to overcome/minimise this problem. I don't believe you mentioned this.
A very good point! Something I have over looked. I remember there used to always be issues in certain areas on the Great Eastern due to sagging wires, that maybe have gone with upgrades to equipment.
I wonder if the increase in the temperatures we are starting to see will bring the issue back or if the tensioner systems have enough in them to deal with a wide range of temperatures
@@thepwayengineer One of the reasons for the Upgrades was to remove the variable tension depending on the weather.
@@thepwayengineeras an Australian (where all metro/suburban rail systems are OHLE) sagging catenaries is rarely an issue these days even on 45°c days!
You’re only ever at the mercy of poor maintenance.
Overhead wire don't sag due to heat or cold, they are counter balanced to prevent sagging, as the wire expands (heat), the weights raises, when the wire contracts (cools) the weights lower! These weights are referred as automatic tensioning weights...
@@A-Trainspotter-From-Berkshire Why remove it when it is 100% proven to work, whet did they replace it with?
One thing to add from a metallurgical and corrosion aspect on third rail. Stray current and grounds have caused a lot of corrosion on buried pipework, particularly around the the home counties area, with the victorian cast iron pipework. So whilst they don't directly affect the operation of the railways, it does pose other problems for utilities, such as Thames Water. Was a case study on my University of Surrey MSc modules about 15 years ago.
Surely AC systems need transformers, whilst DC systems don't ...
well really both need tranformers nowadays since AC motors have become the standard for new Rolling stock
@@cyri96 Inverters needed as well I guess ...
Yup, 3phase AC doesn’t care, the input will be delivered the wrong way, so you need to get the voltage to something reasonable (afaik 300-600V), get it to DC and then invert it to the right frequency (which is a gear ratio and fancy circuiting away from the wheel speed)
the transformer easily changes the voltage of AC to what you need. to do that with DC it requires more complex equipment (on the train). AC motors are the way these days requiring just one (big) capacitor when starting. they also can be wired for a wide range of operating voltages, possibly eliminating the need for a heavy transformer.
@@genoobtlp4424 the AC on the overhead is just single phase. 3phase would need 3 wires. AC motors can be wired and/or geared for a wide range of frequencies easily covering the common ones.
Thanks for this clear info. Growing up in south-east England where third-rail electrification is the norm (and I spotted your Southern train as an example!), I was surprised when I first went up to York as a teenager and noticed the overhead lines and supports on lines north of London. It seemed such a blot on the landscape as well as an unthinkable task to install them all (not that putting in big heavy rails seems like easy work either though, to be fair). You did a thorough job listing the pros and cons, some of which I hadn't considered such as speed restriction.
Like others in the comments, I was confused by trains on the third rail network needing transformers, but I'll leave that to people who know more than me about trains 😅
The transformers are in the feeder stations next to the track.
Great video. Well done. Here in PA, the Penn Central had taken down miles of wire and left the high volt at the top. Here in PA, the wire only goes on amtrk from Philly to Harrisburg PA, but there is a lot of lines missing in the Central eastern part of PA and all thu south Philly. There has been talk running new lines west on NS from Harrisburg, but it just falls on the death doors.
Another disadvantage of 3rd rail is the necessity to leave open spaces at junctions or diamonds. This generates an unstable current supply to the engine (loc) plus numerous electric arc formation... Aside, I fully agree with the fact that supplying current under low or medium voltage is less efficient in terms of current loss by Joule effect. In this line, in France electric locs working under 1500 V need to raise two pantos when starting as the intensity of the current going thru the pantos is extremey high compared to locs working under 25 kV, which is now the standard supply over here...
We have most overhead electrification in Sweden. My last train journey ended up with an overnight hotel stay due to wires being stolen. No trains today due to high winds.
In Switzerland the railways are 100% electrified. Previously, Switzerland used steam locomotives and was dependent on coal deliveries from Germany. This was also the case during WW2, where Switzerland was afraid of being occupied by Germany, which didn't happen. But Switzerland has the ability to generate its own electricity using water. That's why steam locomotives were soon equipped with electric heaters. Because that was ineffective, they then built electric locomotives.
There is another disadvantage of 3rd rail systems I that they are limited in voltage to 1,200V (although some systems have used1,500V) due to earth leakage becoming a significant problem.
To solve the ice problem on 3rd rail the New York Central used under running rails. The contact was on the bottom of rail and the shoe was sprung upwards to contact. This system is still in use on the electrified lines running out of Grand Central Station in New York City. The Pennsylvania Railroad chose over-running 3rd rail for Penn Station in NYC. I believe the New Haven , which served both stations had use 3rd rail shoes that could run on both.
They could install carbon heater pads under the _"third"_
The cost to covert to the bottom contact the third rail from top contact third rail in the UK would be similar to converting OLE. In the UK OLE is the national standard as well as you would save money by using less electricity.
@@A-Trainspotter-From-Berkshire Isn't true, that the lower the voltage, the higher the current? Like 120V~ @ 20A as to 240V~@ 10A or 110.000V~ has low current, until it reaches the sub station, then dropped down to 11,000V~ and then again to 400V~
That's to was the power rating (current) goes up at 630VDC and the 25,000V~ uses less current?
Well bugger. I wrote over-running, that should be under-running. the contact is on the bottom. never comment before coffee.
@@jonathonshanecrawford1840 With 750v 3rd rail you lose about half the energy down to heating versus 20% with 25kv OLE. For example, starting a 750v 3rd rail train takes around 3000A versus 200A for 25kv and 500A for double-headed 25kv.
DC powered third rail type locomotives would not be equipped with transformers, which can't be used with direct current.
Ice breakers can be installed on pantograph collectors as is done in the U.S. for the east coast commuter systems and light rail systems around the country. Third rail systems mostly use 750 volts ac. Metro North rail in New York City uses trains that can run on third rail systems as well as overhead systems of both 12,500/2500 volts.
Interesting about the ice breakers, I haven't heard of them before for OLE systems
Your clip was informative, and you sound quite convincing, yet should we take everything you say at face value? Two examples:
1:43 Apart from this being a skewing tele lens catch, masts do not have to look like that. Germany in particular invested energy in designing masts that have fairly little visual influence on their surrounding. Have a look at the WP article 'overhead line', then click on the german version, then count down to the eighth photo - 'stahlflachmasten deutscher bauart'. [Another way to gather info on this would be via YT, then 'führerstandsmitfahrt' (cab ride).]
Similar masts as the ones used fx in Germany were also erected earlier in Britain. Why did your decision takers not follow course when the Paddington - Cardiff line was electrified? As far as I can see, this question was raised a number of times in the public (maybe not quite as straightforward) but never answered by those responsible.
7:34 Are you certain? There's a tension mechanism, in Germany it has been used since the early days of electrification - the learning phase was from ca 1905 to 1930, since then the overhead system has not changed substantially. (It was copied by most other countries.) If you scroll further down on that same WP page, slightly beyond mid-page to the photo 'radspannwerk DB-bauart zur getrennten abspannung von tragseil und fahrdraht'? And why not use the chance to also note the following image, 'überlappende...'
Ob the topic of Germany, 3rd rail Systems used by the Munich underground and the Berlin S-Bahn, are not exposed on the top. They have a (I assume plastic) cover on top and are So far off the ground that I have seen Rabbits traversing the rails without problems.
@@red_rassmueller1716 still can zap you, even with bottom contact 3rd rail. I prefer the bottom contact 3rd rail that runs at the ceiling as a low clearance OHLE
The Great Western electrification is a 120 mile long eyesore of gallows and goalposts stretched across Southern England.
When you discussed third rail systems,you left out Conduits,and contact systems ! Both had been in use,in Britain and the US! Also those were combined on streetcars/trams,and had long work lives! London,and New York,had miles of those types of operations! Add,on DC operations,there were/are voltage ranges from 600,to 3500,and used on both third rail,and overhead! In Chicago,the former ILLINOIS CENTRAL lines are operated at 3500 volts,and under arduous conditions[lots of snow,ice,and cold],and the CTA elevateds operate with exposed third,as does Boston! Anyway,the history is interesting,and covers some 100+ years of operations! Thank for an interesting video,and you forgot the Liverpool Overhead,as a pioneering rail line! Again thank you 😊!
We've used battery locomotives for almost as long as we've had electric trains. The Hational Collection has a Norh Staffordshire Railway battery locomotive built in 1917, which is about 10 years younger than the NER steeple cab shunter they have.
The third power rail is well suited for subways in narrow tunnels.
A suspended cable would mean a larger tunnel diameter.
There is often no space for this. It is enough for a power rail on the ground.
The local transit agency, BART, decided early on to forgo the old school 600v or 750v third rail and go to 1000v DC third rail. The is sited higher than usual, and contact is by an over-running paddle style contact. They also went with 5'6" guage and non-tapered wheel profile. Who needs 150 years experience.
I think you have that wrong with regard to onboard transformers. Transformers are used to step up or step down AC voltage. They are most definitely required on AC OHLE trains, and not required on DC 3rd rail. where the systems can run at 750V and use more efficient DC - DC converters to step down for equipment like lighting.
To convert DC up or down, first it has to be converted to something like AC (cars do the same (sort of) with the points switching on and off, simulating AC so 12VDC can pass through the transformer (AKA coil), thus "Stepping up" the voltage!
So therefore, low voltage say 720VDC may be needed to be stepped up to 900VDC, to do so, one need to "invert" the 720VDC to say 700V~ (due to loss - normal) then stepped up via a transformer, then rectified to 900VDC.
Bottom-contact 3rd rail is used on modern metro networks, and the S-Bahn in Hamburg uses side-contact 3rd rail.
DC trains do not have transformers, only high voltage AC trains.
I think that suspended bottom contact third rails are the best way to implement a third rail system
Very well explained! (subscribed) At last they're electrifying the transpennine route via Standedge at last and I hope the new government sees the good sense in electrifying the East-West route as well. Very silly not to electrify when the railway is under possession anyway.
Why didn't you mention overhead solid conductor, where you stick a rail on top of the train. It is costly to set up, but is very reliable, isn't prone to the same wind issue and can be used to give very high voltage, reducing losses.
Safety to human an animal life would be my reason for eliminating the use of third-rail. Human life should not have a cost when safer alternatives exist. Thanks for sharing.
Members of the public should not be on the track anyway. Track work is normally done with the current switched off. Live rails in depot are shielded.
i worked a bunch of those empty trains used to keep the third rail from building up ice this past winter.
it required a person to sit in the back of the train and flip a pump switch between left and right output. the pump pushed antifreeze out of a hose connected to each trolley shoe on the rearmost truck. easy way to make time and a half. the rest of the year though, having to walk over live 3rd rail in the yard is a pain. they even set up the grabirons on the side such that the third rail is exactly where you would expect the bottom step of the ladder to be. obviously you dont want to step on it though.
Third rail is 600 Volts DC. The currents are enormous. Voltage drop per mile is high. Third rail requires several feeders from the supplying utility every couple of miles. Expensive electric construction. Overhead catenary in USA is typically 23,000 to 25,000 volts AC which requires utility feed every 10 to 20 miles. There is no comparison. Third rail works on local metro trains, never on long distance without a lot of power infrastructure. Also, because of the high currents at the DC traction motors vs. 2400 volt traction motors in catenary locomotives, third rail engines have limited horsepower. DC third rail is highly inefficient. Ballast resistors on the rolling stock are used to limited current inrush. Once again, great for city and suburban lines, not for long distance high speed rail.
The Railway line through North Wales is not electric, so can only have Diesel trains over here. In the 1980's the train to London would be diesel powered, usually a class 45, or 47, until Crewe, then the locomotive would be changed at Crewe, for an electric one, something like a class 86, or 87.
During the 1990's the HST 125's were put onto the London to Holyhead service, and the same locomotives were used all the way through. Trains from Llandudno used DMU's, and are now using the current version of those.
As the whole of North Wales does not have any electricity on the route, it is suitable for the Steam Special service. This happened in the summer during the 1990's, and was very popular. They still have special steam trains coming through now, but not as often as they were in the 1990's.
@@petermostyneccleston2884 I'm sure Virgin were diesel-hauling a Pendolino set along there at some point in the 2000s. I remember it being an extraordinarily smooth and quiet ride.
@@6yjjk they did do that at some point, but that was the only way that they were able to take the electric train units beyond Crewe.
Electrification of the North Wales coast line would be asking for trouble.
Shout out to the rigid overhead conductor beams. Suprised that didn't at least get an honerable mention while talking about OLE.
Overhead lines definitely need transformers if they are AC. 25,000 volts AC is way more than the train actually needs.
DC is usually 750 volts so a large transformer isn’t required.
1500VDC in Australia, however I believe the long haul European systems use 15KV or 25KV
@@paulstubbs7678 25KV is the standard for overhead lines in the UK. All trains which use overheads in the UK have on board transformers.
@@extrude22 The 1500V is for local passenger services, country, intercity & freight are diesel
There are pantograph contact strips that can be used to remove ice from the wires. Equally there are special inserts for shoes on trolley poles for the same reason. They are made from steel and can withstand the mechanical forces when scraping off ice build up on the wire. However, these are not good for conducting electricity, but when it comes to de-icing, the efficient transmission of electricity is not the main issue.
What about the cost of the metal? Third rail uses a massive chunk of steel whereas overhead wires are much lighter.
There is plenty of steel in the masts and expensive copper in the wires. It gets stolen regularly.
The safety issue for 3rd rail systems can be reduced if using a bottom contact system as the conductor rail can be covered.
Thing about lowering tracks is that it is expensive to do upfront. However, once every 40 years, rails need replacement. And when you are replacing the rails anyway, the costs of placing the new rails a few centimetres lower, to make space for electrification, are negligible (compared to the cost of replacing the tracks). Meaning that these cost of preparing overhead structures such as bridges, can be lowered significantly, by slowly doing it over time, when work has to be done on that section anyway.
Also, newer models of third rail have a collector shoe collecting current from the underside of the rail, allowing for a cover to be placed on top of the rail, making it very resilient to snow and ice.
And electrification has two big advantages: electric trains are cheaper and faster, costing up to 20% less, especially when using ac overhead wires. Second, electric trains need less maintenance, are lighter, and last a good 15 years longer than your average diesel train (average electric train lasts up to 40 years, while an average diesel train only last 25 years).
In the UK third rail electrification on the mainline has to use top contact third rail and the ORR & RSSB will not permit more third rail.
Maybe thats why UK opted for third rail south of the Thames (and a little at Liverpool) because the OLE cannot fit under the bridges. It has to be at least 6m above the rails, hence why new bridges over railways are now required to give clearance for future OLE electrification. it may be the case for the same reason why UK railway electrification is relatively low at ~38%. Therefore, the Midland Mainline, Oxford to Didcot, Bristol Temple Meads to Bristol Parkway/Chippenham electrification projects have been paused with no date of resuming it.
@@annabelholland The reason for the Southern region using third rail is because there were 120 miles of 600v third rail versus 60 miles of 6.25kv AC OLE. OLE isn't 6m the lowest wire height, the foot crossings have a wire height of 5.2m, level crossings have a wire height of 5.6m and the lowest wire height is 4.165m with the standard wire height being 4.7m. The only time when an OLE wire is height than 6m is to trip the Over Height Drop system which will drop the pan at 6.2m. The reason for the cancelling has nothing to do with wire height and everything to do with the former government didn't want it. Labour has plans to restart the electrification projects as they were mostly finished. Bridges only need a gap of 70mm between OLE and the bridge, for example, the Cardiff Intersection bridge has an air gap of 70mm and a wire height of 4.165m. The Southern Railway by the 1940s regretted their choice to go with the third rail system rather than the OLE system. Also, Network Rail recommends the replacement of most of the third rail with OLE. Merseyrail also could fit OLE in. There is only a few lines which would keep third rail and that is the Island Line, Northern City Line and London Underground shared sections. Island Line and Northern City Line are due to the small tunnels which will not fit normal trains in.
@@annabelholland yes and no, the uk initially opted for third rail, because of the many tunnels and bridges, but also because overhead lines usually use AC systems, which were very expensive and unreliable in the 1900's.
Third rail was only placed in the southeast, because those lines were electrified first. Afterwards the development of reliable higher voltage systems lead to the uk preferring overhead line for new projects.
Also overhead lines are placed between 4.60m and 5.10 m in the UK. While in mainland europe the wires are placed between 5.10 and 5.60 m. With most high speed lines having the wire at 5.30. (This height difference is why mainland europe can have double stack trains.)
I meant that the bridge should be at least 6m clearance above the rail, not the wires. I am not the best at railway electrification stuff. For comparison, bridges over road that are under 5m tall (16'6") have to be signposted. so that drivers of vehicles that exceed the height limit can find a way around it. This is why large vehicles colliding with bridges happen every so often (at least once a week) and most of them are railway bridges. But anyway, third rail electrification may be cheap at first (because no bridge raising/modification, track lowering, OLE installation, etc) but gets expensive long term because there are also so many substations (roughly every 6km), low effieiency, and cannot really go above 100mph. Plus the risks with staff and the public. Even small extensions/new stretches of third rail are/may not done. The Severn Tunnel had just enough clearance for OLE (possibly requiring track lowering), even though it was built over 100 years ago.
There are 3 types of 3rd rail, top contact, bottom contact and side contact.
For areas with less frequent services it has been suggested that trains that can run on battery mode for the length of the line and then charge up when on "mains" are a way to reduce diesel powered trains.
I honestly didnt know there were three different types, thank you!
@@thepwayengineer Are tracks your personnal area of expertise, as I had first assumed when watching you channel ?
@@constancel4211 It is indeed
I've often wondered ( and perhaps an engineer can enlighten me ) regarding 3rd and 4th rail systems. If metal shoes are held against the live rail by a spring or similar means, and the train can run up to 85mph, then why don't the shoes heat up through friction and even start to glow red hot?
One more disadvantage of the overhead power lines you didn't mention is the height restriction on the trains themselves. Double decker freight trains cannot run on those lines.
@larryppe in countries like India where people ride on top of trains often, overhead power can be a big hazard. i've seen a video showing such an event.
@@philhoward4466 Also in India - they run double stack container trains under overhead wires: th-cam.com/video/3BbdDzkMYJs/w-d-xo.html
We need to have a pro-rail government that creates a rolling program of railway electrification.
A rolling program of electrification will increase the amount of work being done and lower costs. The Scottish Government has already been doing some of this north of the border with England and their rail experts have been able to work out a system where equipment is pre-installed on electrification masts to minimise the number of closures needed to get overhead electrification put in.
Overhead rail electrification needs to be done on the basis of the best early impact. So a lot of it is going to have to be based about removing diesel pollution from densely populated areas. But you can not run an electric fright train if part of the route is an "electrification desert".
Third rail needs to be banished from the UK. It's already illegal to install new bits of third rail (it can only be repaired). However, it is far more important for us to decarbonise, as quickly as possible. So priority needs to be given to electrifying non-electrified routes and a plan to eventually pull up third rail and replace it with overhead electrification should be tied in to routes like Thameslink, where we currently have trains that switch between both systems.
If we electrify most of England, Scotland and Wales (Northern Ireland also needs to be electrified, but uses different trains) we could have enough spare trains to cover the third rail sections transitioning over to overhead electrification later.
I have no idea how one would go about replacing the 3rd (& 4th) rail of the London Underground, especially the tube lines.
New third rail isn't strictly illegal, ORR's position is a bit more nuanced than that, new third rail would have to be justifiable. Wholesale electrification of the mainline isn't going to fly, but small extensions are potentially acceptable, as is LU and DLR extension, since those are safer systems. LU doesn't do live working, and DLR is bottom contact, but both have better separation for staff and the public from the conductor rail
Rail accounts for 0.7% of UK emissions. Nobody should be wasting time talking about decarbonisation of rail. Overhead electrification makes the railway unreliable. I have personally been caught up in a couple of nasty incidents in Sweden due to OHLE failures, and I don't travel very often. All trains in Western Sweden were cancelled today because of the wind.
Electrified third rail is a useful safety feature: it discourages trespassing. Fatalies at Southall and elsewhere were caught by the lineside masts. The RSSB needs to be challenged on this and other issues.
Why does NI need to be electrified?
3:04 The commonly held belief that transmitting DC is less efficient than AC isn't necessarily the case. Whilst this was true many years ago, we now have technology that is being used to transform DC voltage up and down at transmission line capacities.
It's not just about transformers. Long distance high voltage DC transmission is great for sending very large voltages over major transmission lines, suspended from large towers running through cleared rights of way connecting places of supply and distribution that are a very long way apart.
The same technology is not optimised (and not economically adaptable) for supplying suitable voltage connections to train systems at points that are relatively close together.
In the past something like 750 or 1500v DC was the best option. In the last several decades higher voltage AC technology has developed so that it is the 'go to' system. and 25v AC is easily drawn from typical public power grids and suitable for overhead wire supply.
Thanks for this video.
It's the most balanced treatment of the ups and downs of either one that I've seen.
Thank you also for packing in so many nuggets of information whilst keeping the whole thing entertainingly speeding along down the track.
Can it _really_ be because of the impact of pick-up shoe to next section of 3rd rail that top speed is stubbornly stuck at 100mph‽ Can't find anything else online.
Not a fan of all the gubbins that comes with OLE for possibly facile visual pollution reasons, I can't help but think that it's about time that entirely different ways to get trains moving should exist by now.
It cannot be beyond the wit of man to come up with an onboard energy source, non-polluting, negating the need for any of it to be installed, maintained and child/idiot/accident - proofed in the first place.
Thank you for the kind words!
Having been next to a train when it is running at a fair speed, they do hit those ramps pretty hard!
Railways account for 0.7% of UK emissions. Why is anyone concerned about this?
We in Sweden have large scale overhead electrification. It is grossly unreliable. My last journey ended up with an overnight hotel stay due to the wires being stolen, which happens regularly. A previous journey ended up with four hours in a forest waiting to be rescued. No trains in Western Sweden today due to high winds.
A lot of the electrification in Sweden could usefully be removed when it wears out.
There are very few fatalies to staff due to 3rd rail electrification. It is easy to shield the live rail.
Overhead wire don't sag due to heat or cold, they are counter balanced to prevent sagging, as the wire expands (heat), the weights raises, when the wire contracts (cools) the weights lower!
I believe you have the weights reversed from what they actually do. Yes, wire and other items expand on heating thus sagging, and contract on cooling thus raising. All of the catenary and other overhead wire systems that I have seen, use weights connected to the contact wire to provide a more-or-less constant tension in the contact wire for the overhead system at uniform spacings.
@@royreynolds108 Thanks for the correction, at least you understood ! The same here in Australia and New Zealand we still use weights and pulley system to ensure the tension is kept constant!
Why would Network Rail _(UK)_ abolish a system that has worked for decades?
If the third tail is DC, why are there transformers in the train. Transformers only work with AC?!?
The fundamental focus of this comparison is flawed. The pretty much universal opinion today is that high voltage AC based rail is the best option overall in terms of potential performance - in situations where speed and/or haulage capacity are paramount and, most importantly, when addressing a green fields, first-time electrification scenario. But, in order to put the options into true perspective, one needs to go back to the conditions that prevailed when practical electrification initiatives were first mooted. For a start, 25kv OH did not exist as an option to the best of my knowledge. Certainly the pioneer overhead schemes like the LBSCR used DC through their wires. Also, and most importantly, electrification as a concept was developed in response to serious revenue losses to other forms of passenger transport. It had to be done, but it also had to be done as cheaply as possible - which put the third rail firmly in the driving seat. And, finally, it must be remembered that the third rail has always been focussed upon a specific aspect of rail operation; relatively short distance travel patterns needing frequent service intervals, where capacity, reliability and cost are the primary determinants, rather than speed and electrical efficiency. And, when looking at the UK in particular, one must always look at where and how such benefits as speed or haulage capacity are paramount. Third rail can manage 100 mph although generally limited to 90. Outside the two main northern lines, there's not a lot of the network where higher speeds than that are feasible, necessary - or even electrified...
So I got interested in your PDFs, but.. £25 for three PDFs, no info beyond an of the front page. No info on number of pages, no preview, no info on terms for the purchase etc.
No deal for me.
Hi Dave, I am sorry to hear that. I will take that feedback and look to see if I can address it in anyway
High Voltage centenary systems (most common) REQUIRE a hV to lV transformer associated with the engine. A paragraph is diamond shaped device, where a flat framework is more of an energy collector. Ron W4BIN
You have mixed up the term transformer and inverter. The transformer is used on ac systems to drop the 25kv down to around 1kv for the traction system. Dc systems use an inverter to convert the 600 to 800 vdc to ac for other systems. All modern trains first of all make dc on board and then convert it to different voltages and frequencies for the auxiliaries and traction supplies. Dc sub stations now have inverters to convert the regenerated dc into 50 hz to pump back into the grid. It’s a lot more complex than your explanation. Also you might ask why DB and SBB etc use 16 2/3 Hz. I could go on for hours on that subject, but it is actually a more efficient system. AND it allows regeneration into an ac oh without semiconductors or rotating converters way back from the 1920’s.
the lower the AC frequency, the larger the core, and thus heavier, for the same voltage and power.
Despite the over-engineered, over-expensive GW electrification, its resilience to damage is appalling, as was proved earlier this year.
For high speed lines, there is no alternative to overhead supplies (unless using diesels as per class 43), but in urban areas with clearance issues and potentially lower speeds due to track geometry, third rail might be a better option.
The class 313 trains on the Moorgate branch and the dual voltage Javelin trains in Kent both on HS1 and the 750V dc network have shown that the systems work well. Perhaps the lines through Bath could have been electrified this way, cheaply and without upsetting the sensitive eyes of the Nimbys?
One point regarding efficiency- Overhead line are not more efficient due to being on AC, but it is because the very much higher voltage possible reduces the current required, and thus resistive losses, so a smaller conductor can be used. It is only required to be AC in order to step down the voltage via a transformer on the train to a usable working voltage. (Note that Belgian Railways used 3000Vdc overhead but would still need to have a current carrying capacity 6 times higher than that of 25kV system).
The major problem with conductor rail electrification is safety, and for that reason it's quite difficult from a regulatory point of view to extend existing lines, never mind new electrification schemes. Personally speaking, I don't think myself or my colleagues should be electrocuted at work to protect the sensibilities of nimby sorts!
@@mrikoantal The problem with using safety as a reason for not using third rail is what do you do about systems already in widespread use? e.g. Merseyrail, Northern City Line, Glasgow Subway, London Underground and Overground, plus the huge ex-BR SR network. Do you shut them down because they are unsafe? Track Staff should have safe working methods in place (I have personally worked on live systems under strict safety procedures), but trespassers deserve Darwin Awards- I have no sympathy for them.
The risk of unintended contact with the third rail can, however, be mitigated by timber shrouds, as already used in some locations.
My intentions were to avoid the huge cost of raising bridges (and their parapets because idiots still manage to electrocute themselves on the overhead wires).
In the Bath area, the track curves would prevent high speeds anyway, so third rail is quite satisfactory for speeds up to 160km/h.
I actually share your views about Nimbys. They have cost the country dearly with the HS2 tunnelling so I really don't care if they are upset, but they would certainly have less about which to complain and hold up progress.
@@MervynPartin I generally agree with the ORR policy statement, I'd say. From their point of view, the existing mainline network can stay with small extensions and upgrades and so on, but newer stuff has to be safer. They rate LU and DLR as being safer than mainline third rail, at that. They're not proposing tearing down the former southern region, but a new top-contact scheme isolated from the wider network would be very hard to justify, even if every inch of it was boarded. We're trained on safe working, but if you're placing interlocking shrouds down straight on top of the conductor rail, and have to get them off when a lookout blows you out, it's another thing that can go wrong.
@@mrikoantal
Electrified third rails discourage trespassing. That is an important safety feature.
Electrification masts are a hazard in themselves. Fatalies at Souhall and elsewhere been due to impacts with masts. The attitude of the safety authority is inconsistent.
@@MervynPartin
The whole GW route should have been done on 3rd rail long ago. Apart from the other advantages it would then have been compatible with Southern and London Underground routes. The Elizabeth Line would have been less expensive.
Longer heavier freight trains tend to be diesel electric aren’t they?
2:50 this is misleading, the class 387 which is primarily used on the Gatwick Express has a top line speed of 110 mph, that’s only 15 mph slower than most high speed trains in the UK.
Gatwick Express is limited 90mph as that is the top speed of the Brighton Mainline and 387s are limited to 100mph on the third rail.
There is new generation of train motive power other than diesel and full electrification being electric/battery, electric/hydrogen fuel cell, electric/hydrogen fuel cell/battery and hydrogen fuel cell/battery.
You can't use a transformer with DC, they need AC to work.
3rd rail is underrated IMO.
Yea. Toasted eejits on the track is actually the third rail system performing a valuable evolutionary function
3rd Rail is unsafe.
@@A-Trainspotter-From-Berkshire
You shouldn't be on the track anyway.
@@physiocrat7143 Hidden London runs tours on the East London Line track.
Since most diesel trains are actually diesel-electric wouldn't a hybrid system be more optimal? Run the trains on diesel when out in the country where electrification would be expensive. When approaching a city, connect to electric and not have the emissions and noise associated with diesel in a confined area. Many jobs could be created modifying existing diesel to connect to 3rd rail or overhead wires. Seems it may be less expensive than building new engines from scratch.
The UK has such a limited loading gauge that it wouldn't work for conversions. For example, the British Rail Class 769 was a total failure which was converting a dual voltage electric unit into a tri-mode unit.
It is a question of pollution, particularly in terms of CO2 emission. If your electricity supply mostly relies upon non carbon sources (e.g. reniewable or nuclear), it's better to avoid to use fossile fuel to power trains, whatever the location (countryside vs. urban environment). The only advantage of Diesel engine is the lack of necessary equipment on the tracks. This is a reason why it is still widely use over the world, but it remains anyway a source of pollution.
@@yvesd_fr1810 In the UK electricity must be 10% cleaner than fossil fuels.
No country except Britain supplies main railways with a third rail and such a low DC voltage. On the continent, several countries leave their existing DC systems (1,5 or 3 kV) replacing them with 25kV 50Hz for high-speed trains as in France and Italy. Conversely, you rarely find urban underground railway systems without a third rail.
Interesting! Thank you for sharing
True, and this is also because of the given power from any current vs voltage. High current / low voltage needs “thick” cables (practically, third rail) to carry the same “horsepower” (ok, (k)Watts) as a low current / high voltage across a thin (way cheaper) conductor (catenary, never 3rd rail for kV).
Watts (P) = Amperes x Volts (except losses, AC power factor, impedance, Eddy, r-emf and lots of other crap…😅)
@@musiqtee Thanks for explaining that to an engineer for electric energy. I even learned to calculate a railway motor 16 .7 Hz & 1000 kW fifty years ago before electronics entered the locomotives. But these have a similar problem as their Voltage was limited below 600 V. But these locomotives have a transformer down from 15kV.
But anyhow, supplying main railways with 750V is odd.
@@gottfriedheumesser1994 Slapping my forehead hard… I meant to explain to the channel’s creator comment… Sorry for that.
But yes, there are some (very few) “dumb” systems actually running out there. Most could be “explained” from them being quite old (tech available at the time), and too expensive to change/redevelop.
True, I don’t know of any low voltage 3rd rail systems using AC. Seems like an engineering nightmare for reasons you know better than I do…
@@musiqtee I is the dust and safety problem. Although the current rails in Europe are protected by a plastic housing against being contacted from the top and aside, their insulators are affected by moisture, dust, and dirt and cannot withstand higher voltages.
In the emperor's times, the trams on Vienna's Ringstrasse should not have overhead lines. So they invented a third rail system where the current rail was situated in a small tunnel below the driving rail which had a slot for a contacting device. But this was very misfunction prone, and shortly after the Emperor was gone they installed overhead lines at the Ringstrasse and installed normal tramway rails.
maintenance trains could be battery powered instead of diesel powered. EVs have created a market for improved battery technology.
London Underground has had battery electric locos since the 1920s for maintenance trains.
You mentioned ( BATTERY ) electric trains ... GWR ( UK ) are using old D78 LUL rolling stock to see if this is feasable for rural routes .... the BIG , BIG snag with overhead lines is simply that they are ( REALLY , REALLY UGLY ! ) , much like the electric trolley bus nightmare in SW London ( Surbiton ? ) in the 1960's ... FYI , the London Underground uses 4 rails to keep the track current AWAY from the running rails ( this avoids subsurface ringpiece corrosion ) . ( ? ) ...... DAVE™🛑
The reason is so that they are nice and strong so that if a wire breaks trains can still use the other lines which isn't possible with lighter OLE like on the East Coast Mainline.
As a yaw damper salesman I would like to thank all railways that use 3rd rail.
How do they work out how much electricity a train is using - e.g. do electric trains have 'meters' and does the operating company get a bill?
Many electric trains can actually put electricity back INTO the system as well as use it of course (from regenerative braking systems)
I'm trying to not picture a driver pushing 50ps into a meter but it's hard not to ;0
Overhead lines aren't part of the power grid, they connect to the national power grid in determined places called electric substations, which are facilities meant to provide the adequate voltage and current to the overhead line/third rail. The meters will be placed there.
One disadvantage of third rail is that it runs on lower tensions (750v typically) which requires a closer spacing of substations (each of them a few kilometers appart). With 25kV overhead line, substations can spaced much farther, with 20 to 60km between two substations. Substations are expensive facilities and the fewer the better.
@@constancel4211 Also with 750v you need Track Parrealling huts.
@@constancel4211 None of that explains how they know who's trains are using the electricity...
All main lines have multiple operators using the power and I don't imagine they get the electric 'for free' - at the same time, operators using diesel won't want to be paying for the overhead electricity I imagine...
Freightliner mothballed some electric locos a few years back due to the cost of running them so they DEFINATELY aren't getting it for free!!
My guess is there'll be a cost-per-mile or a pro-rata cost but - historically - train engineering tends to the overcomplicated so I wouldn't be surprised if electric trains don't have to track their usage and pay accordingly..
@@dizzy2020 Sorry I forgot the scenario where multiple operators share the same tracks. I don't know how the do it. I'd guess that would be based on train tonnage per miles travelled but perhaps they do have a meter somewhere.
Never seen a 3rd rail until I came to the poverty stricken UK. Nobody even told me of the danger. Now they have fibreglass covers, safe and good for metros.
Third rail systems are used in parts of the United States as well, notably near New York City.
Isn’t the Toronto subway system 3rd rail?
Copenhagen Metro uses covered bottom contact 3rd rail. You can't do that with the top contact systems used in the UK.
@@neiloflongbeck5705 Seen that in Berlin and later on some Delhi metro lines.
One advantage of desil is that it’s more power efficient because the electricity to power the generators which moves the train is generated locally instead of 200 miles away in a power plant.
Who is desil?
"Being DC, 3rd rail is inefficient."
Ba-bow!
No, Being a lower voltage, 3rd rail is inefficient.
AC or DC has nothing to do with it. End of.
Third Rail is also a trip hazard.
But the running rails aren’t a trip hazard?
@@John.Mann.1941 Indeed. But Third Rail, unlike running rail, is discontinuous and switches sides. I have seen maintenance workers adopt a 'tall stride' when crossing the rail. Also, have a look at systems like New York Subway and Long Island RR. The Third Rail is further away from the running rail, and is covered by a board. Jamming your foot in between the rails is less of a problem, but you've still got to step over the thing. There is also the possibility of catching your toe under the board. There are plenty of pictures and video online of staff standing on the board! And I haven't even touched on the trailing cables, hook switches, etc.
Third rail seems like it should be more dangerous in principle, but what about in reality? Are there an appreciable number of injuries caused by third rails every year?
In recent years Network Rail has moved toward all working being done in possession with no trains running and the 3rd rail isolated.
Prior to that I know of two instances of people directly that came into contact and suffered injuries from it. While there are mitigations, such as shields, there is always an element of risk working around live equipment
It's bloody dangerous in reality, passengers and trespassers don't always appreciate the risk, and if they get in contact with the conductor rail, it's potentially game over for them. Not so much a risk under wires, not many trespassers are pole vaulting or abseiling onto the railway. This is also reflected in how infrastructure staff training is done in the UK, the third rail safety competency (DCCR) used to be delivered as part of PTS, it's done as a distinct competency now.
@@mrikoantal I get that, it’s just that where I grew up we were constantly warned by the adults about being electrocuted by the third rail on the railway through the town. I guess that just conditioned me to assume that people were being killed by the dozen by third rails.
I'm not sure how it compares in terms of stats I'm afraid, I've had a look and as far as I can tell the ORR doesn't generally record cause of injury in its injury/death stats
It’s my understanding that on the London 4th rail system the train were equipped with shorting bars which train staff could place across the power rails thereby tripping breakers on the power supply. This left the tracks dead. This was to provide for safe evacuation of a train in emergency situations. Weren’t the stations also provided with means to kill the power in emergency? My information may be out of date, I’ve lived in Canada for 57 years, but I used the underground a lot as a child and youth - very inexpensive using the staff discount my father got for the family (he worked at Acton for most of his working life).
Discontinuous electrification (OHLE) could be the future if the DfT realised the opportunity. Several bi-mode fleets (with battery propulsion) are already in service and most the Hitachi class 8xx fleets can retrofitted as such. It’s not necessary to install a huge battery capacity, as the concept is to reduce infrastructure build time & cost by skipping OHLE installation on the complexed track sections such as tunnels & bridges. So you only need enough battery capacity to get through those resulting unwired sections. And….
Rolling Stock fleets which have propulsion batteries have an ease of maintenance advantage too, because they can be moved around unwired sections of their maintenance depots without any shunting loco. Trains can also reach a station or siding when there’s an OHLE failure.
The main point I got from this video is that overhead is 100% safer than third rail! I believe more people are killed by 3rd rail than overhead, I have never heard (under normal condition) being killed by overhead wire, just look at our streets where there are power polls! And yes idiot drivers (drunk and/or stoned) crash into power polls and cause the 11,000 & 400V wire to come down! Don't blame the trees, when trees fall onto power wires, blame the people that suppose to maintain the area!
Electricity and water do mix.... and that's the problem.
This is a point! Not a sensible mix I should have said!