How Trains Are Powered on the Railway | Third Rail vs Over Head Line Wires

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.

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.

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.

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.

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.

I live near Toronto, Ontario. At the moment, a new LRT line is being installed right down the street in front of my condo. They are going with a pantograph system and will soon be installing the wires. In Toronto, the subway system uses 3rd rail, but the streetcars recently switched from trolley pole to pantograph. The new LRT lines in Toronto will also use pantograph.

Surely AC systems need transformers, whilst DC systems don't ...

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.

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 😅

Here are three things you missed: 1) Floods will also affect most overhead wires. In both third rail and overhead lines, the power returns on the running rails so if the track is flooded even overhead wire will be taken out. The only way around it would be to have 2 wires overhead. That hasn't been used much on rails but it is necessary for trolley busses. 2) A trolley pole can also be used for overhead wire collection. I think they are still used more here in the US but even here they are mainly used for museums and heritage streetcar (aka trolley, tram) lines like those in Tampa, FL and Memphis, TN. There have been other methods like the bus bar (that may not be right) which is a loop of metal that contacts the wire like a pantograph but has little support hardware like a trolley pole. This method is pretty much extinct as it was mainly used as an intermediate step between trolley poles and pantographs. 3) Another issue for overhead wires is that it restricts the loading gauge. Here in the US, most trains that carry intermodal containers are double stacked containers. In areas with overhead wire, (primarily the Northeast Corridor and some suburban electrification) only single stack containers can be run. Similarly, Amtrak's Superliner cars and other bi-level cars can't run on the northeast corridor either. That is not as much of an issue in Europe and the loading gauge from other factors limits containers and passenger cars to single level. This is not insurmountable as the Metra Electric lines in Chicago, IL run bi-levels and some French TGV's are bi-level. Of course, the wire much be much higher to allow for high height cars and thus is best done before the wire is strung. Raising the wire height significantly will usually require larger pantographs and will often require modifying bridges and tunnels or lowering the track to make the required clearance. This is not unique to overhead wire. The US railroads have spent millions if not billions of dollars to increase clearances to permit double stacks in non-electrified territory as well.

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.

DC powered third rail type locomotives would not be equipped with transformers, which can't be used with direct current.

around NYC they have some trains that can run overhead and third rail as well as diesel locomotives that can run diesel or third. Dual Power diesels for example run up the Danbury branch of the New Haven line as the branch has no electrification but you also cannot run a diesel into Grand Central. So the locomotive cuts the engine and runs on the third, The Overhead and third trainsets are because the NH line shares most of its track with the NE corridor which is overhead, but the Metro North lines into NYC are all third rail.

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 😊!

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.

If the third tail is DC, why are there transformers in the train. Transformers only work with AC?!?

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.

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.

Very excellent explanation for a novice rail enthusiast like me!!

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...'