Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Dublin-Cork Railway Line

Options
13»

Comments

  • Options
    #62
    cgcsb
    Registered Users Posts: 9,395 ✭✭✭cgcsb


    we already use overhead power, why now switch to third rail?


  • Options
    #63
    stehyl15
    Closed Accounts Posts: 598 ✭✭✭stehyl15


    cgcsb wrote: »
    we already use overhead power, why now switch to third rail?

    Only the dart has overhead power the cork line could use third rail as it is not electrified and third rail is cheaper to install


  • Options
    #64
    Pablo Escobar
    Registered Users Posts: 644 ✭✭✭Pablo Escobar


    Idbatterim wrote: »
    the problem is, you cant get from Cork city centre into the actual centre of Dublin, where most will want to go, without getting off the train and making another connection... The train being able to go from centre to actual centre, would improve its attractiveness IMO...

    This improvement is aimed at improving the attractiveness of local commuter rail first and foremost IMO. It'll have less of a psychological impact on people travelling further.


  • Options
    #65
    GerardKeating
    Registered Users Posts: 7,626 ✭✭✭GerardKeating


    stehyl15 wrote: »
    Only the dart has overhead power the cork line could use third rail as it is not electrified and third rail is cheaper to install

    Actually, it would be more expensive.


  • Options
    #66
    cgcsb
    Registered Users Posts: 9,395 ✭✭✭cgcsb


    stehyl15 wrote: »
    Only the dart has overhead power the cork line could use third rail as it is not electrified and third rail is cheaper to install

    3rd rail is more expensive generally, it was used in London to save space in 19th century underground tunnels. Dublin-Kildare will need overhead to accommodate DART anyway, so no point switching to 3rd rail.


  • Advertisement
  • Options
    #67
    MrMorooka
    Registered Users Posts: 710 ✭✭✭MrMorooka


    Third rail systems will not be used for a new build these days, it just won't. It's only used for legacy reasons- eventually the extensive network in the UK will be changed over. From what I gather, it is a very inefficient system that struggles to provide enough power for modern trains with A/C and fancy electronics etc. There's also the problems associated with having a high power conducting rail on the ground, for trespassers and staff on the line etc.


  • Options
    #68
    L1011
    Registered Users Posts: 68,545 ✭✭✭✭L1011


    stehyl15 wrote: »
    Only the dart has overhead power the cork line could use third rail as it is not electrified and third rail is cheaper to install

    Third rail isn't cheaper, and its not really suitable for long-distance use either. There is a reason that catenary has long since replaced it outside of metro systems and the former Southern BR region.


  • Options
    #69
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    I think third rail would possibly even be illegal under modern electrical safety law. They're "grandfathered" in some networks because the cost of replacing legacy systems would be astronomical and it would be highly disruptive.

    You'll never see new 3rd.rail.


  • Options
    #70
    Lenton Lane
    Closed Accounts Posts: 100 ✭✭Lenton Lane


    SpaceTime wrote: »
    I think third rail would possibly even be illegal under modern electrical safety law. They're "grandfathered" in some networks because the cost of replacing legacy systems would be astronomical and it would be highly disruptive.

    You'll never see new 3rd.rail.

    Third Rail isn't an option for long distance railways and it is as other posters have said a legacy system from the past. There is associated with 3rd rail DC systems the need to build a chain of substations along with the electrified rails.

    The real issue for Irish Rail is that the Dart isn't standard 25kV AC either. It's 1500v DC Overhead which isn't suitable for Long Distance trains and generally not standard these days. There may possibly be a need in the future to convert the Dart system to 25kV AC, as and when the current trains need to be replaced.


  • Options
    #71
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    Even some metros like Madrid converted to overhead power.


  • Advertisement
  • Options
    #72
    dowlingm
    Registered Users Posts: 5,328 ✭✭✭dowlingm


    Plenty of European trains can handle 1.5kV DC/25kV AC. Mostly locomotives but the French SNCF B82500 class is an EMU example - in fact it can do diesel too! 25kV would be tough to convert because you need bigger wire clearances from structures so much existing DART stuff might have to be ripped/replaced.


  • Options
    #73
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    Most countries have a mixture of voltage on their rail networks.

    It's not a significant technical challenge especially as any electric intercity trains won't be running at full speed across the DART area anyway. 1500V DC is a bit limited for high power draws.

    25kV AC is the norm for long distance though for new construction.


  • Options
    #74
    Lenton Lane
    Closed Accounts Posts: 100 ✭✭Lenton Lane


    dowlingm wrote: »
    Plenty of European trains can handle 1.5kV DC/25kV AC. Mostly locomotives but the French SNCF B82500 class is an EMU example - in fact it can do diesel too! 25kV would be tough to convert because you need bigger wire clearances from structures so much existing DART stuff might have to be ripped/replaced.

    The insulators are also a key part of conversion. Generally the structures on the Dart are well constructed and I wouldn't expect that there would be a huge amount of re-engineering needed. Clearly the knitting has to be replaced but I would expect some refurbishment at this stage.

    While dual voltage stock is also possible it makes more economic sense to reengineer the full network to 25kv ac if the Belfast line is electrified and Dart Underground comes into existence. The ultimate aim should be to have a standard electrification system rather than trying to reverse engineer to ensure legacy stock is catered for.

    Back in BR days the Manchester suburban lines were converted from 1500v DC to 25kv AC without the need to rip up and massively re-engineer structures.

    Irish railways are historically plagued with short term thinking to save money which leads to bigger and more expensive resolutions at a later date.


  • Options
    #75
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    The issue is that the DART fleet is the largest set of stock IE have. So the relatively cost of retrofitting 52+ trains for 25kV vs purchasing new trains that can handle 25kV and 1500V would have to be weighed up.

    The Cork-Dublin line and maybe Dublin Belfast might be logical lines to electrify. By international standards they're not very busy and you could be taking about a combined fleet of 16 trains or so.

    Due to massive improvements in solid state power systems and the large amount of space on trains, this isn't generally much of a challenge.

    Most long distance electric trains handle more than one voltage / frequency.


  • Options
    #76
    dowlingm
    Registered Users Posts: 5,328 ✭✭✭dowlingm


    Refitting to 25kV might work if all replacement DARTs, such as when the 8100s are replaced, are specified as dual voltage. Immediately though unconverted 85xx trains would be precluded from working on rewired areas. 25kV transformers are not small or light so it's unlikely that refitting the 8500s would be easy if even possible.

    Switching voltages isn't a minor thing either, even though it is widely done. When Amtrak introduced the new Siemens Sprinter locomotives it took them a while to work out the bugs in switching from legacy New York Metro North area 12kV to more recently installed 25kV east of New Haven towards Boston.

    EDIT: one of the main reasons for working with high voltages is that you need way fewer substations and thus grid connections over the same distance.


  • Options
    #77
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    Main reason is to reduce the issues with getting power from the wires to the train. Increase the voltage 20X and you decrease the current by the same factor.

    This means fewer, less complex pantographs, smaller, lighter contact wires and way more power.

    Using AC means you don't need complex AC to DC conversion and can just can just use normal power at 50Hz straight from the Eirgrid/ESB network.

    Older trains used DC because modern variable frequency / variable speed AC drives weren't cost effective.
    A modern train uses solid state rectifiers other gear that basically allows it to send different frequencies of power to the motors.

    That technology became cheap and reliable and is even used by modern washing machines with "silent" drives.

    It's also made things like hybrid car power systems possible.

    You would possibly be able to order AC/DC trains for the Northern line and 25kV 50Hz for everything else.


Advertisement