Electrification Engineering - General

Discussion in 'Infrastructure & Stations' started by Joseph_Locke, 10 Jun 2018.

  1. Joseph_Locke

    Joseph_Locke Established Member

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    Since I've been told off for using an existing thread, I'll start a new one.

    1. This would be true, but bridges have interminable lifespans (120 years) so rarely come up for reconstruction at the right time (vide Lever Street on Manchester-Preston). Secondly, unless there is an active electrification plan, the Civils Asset Manager will never get funding to speculatively raise a bridge (unless it was cheaper to do it that way). Speculative wiring would only really be advantageous of each end of the new wire joined two places up (which might involve rebuilding, track lowering, etc. way beyond the bridge in question.

    2. Some things are mandatory (when present):
    • Providing vertical headroom for the OLE
    • Finding somewhere to put the switchgear, feeders, etc.
    • Providing the OLE
    • Immunising the signalling system against 25kV induced voltages
    • Protecting the signalling maintainer from the OLE (these last two sometimes trigger a resignalling of the line)
    • Gauge clearing the route for the new electric rolling stock (generally fixing issues with platforms)
    • Upgrading the earthing arrangements for station furniture, CIS, etc. and for fences and pipelines in the vicinity
    • Raising parapets to comply with GL/RT1210
    Things like speed increases and track renewal aren't a direct result of electrification, though advantage is often taken of the better acceleration curves of EMUs by doing so. Track renewal is typically a function of any speed increases and increased timetable frequencies. This latter is also the main trigger for closing footpath crossings, as it raises the risks, but the potential for fishing enthusiasts to zap themselves with carbon fibre rods has been another.

    3. This depends on what performance you're wanting to buy. Current bi-modes are OK-ish EMUs with diesel donkey engines, good only for the smallest of gaps and useless on any kind of hill. If you went for a class 220 with a pantograph car added then perhaps this might perform better. Any change to and from OLE is best done stationary (to avoid embarrassment) so perhaps the IPEMU concept might be a better bet, as it doesn't involve starting diesel engines.
     
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  3. GRALISTAIR

    GRALISTAIR Established Member

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    Thanks for starting this thread. I will pin it in the the pinned thread in a few days time.
     
  4. GRALISTAIR

    GRALISTAIR Established Member

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    So to keep this simple it has been 25 years since I rewired a house in the UK. Radiators central heating the earth/equipotential bonding wire had to be 6mm^2 but the main gas line in and water line and iirc the shower had to be 10 mm^2 . So when electrifying at 25kV the earth/equipotential bonding wire/other has to conform to certain requirements? Not to get too far OT so the Forth Bridge would need the mother of all earthing arrangements if it got electrified?
     
  5. edwin_m

    edwin_m Veteran Member

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    Any metal items in the vicinity of the 25kV line have to be bonded to the rails to prevent dangerous voltages arising. There are also precautions such as bonding across any metal items that run parallel to the railway before cutting them (otherwise a dangerous potential could build up between the two sides). I would have thought the Forth Bridge, being a continuous metal structure, would only require a few earth wires.
     
  6. Joseph_Locke

    Joseph_Locke Established Member

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    If you think so, check out the network arch span of Ordsall Chord, down near the deck: every tie rod is bonded, twice. It seems overkill to me ...
     
    Last edited: 10 Jun 2018
  7. Joseph_Locke

    Joseph_Locke Established Member

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    And this brings me neatly on to the next highlight of our tour of electrification schemes: legacy non-compliance.

    If a situation exists that was compliant to standards when built but isn't safety critical, then it will have what's called grandfather rights. In summary, that means all is OK until you try and alter it, at which point you have to bring it up to full compliance with current standards.

    Electrification is so invasive that it leaves no grandfather's rights intact, so such projects spend a great deal of time fixing things that aren't actually broken. Consider station lighting: lamp post probably just earthed via the supply cable (if at all, as we have discovered). OLE-standard requires a much more robust earth than 10sq. to resist a 12kA fault current* - outcome = dig up the platform and provide a new duct route just to get the earth cabling in. Repeat for every other electrical circuit on every station ... and work out how to avoid sending a 12kA fault current back up the DNO cable!

    * if it's in the fall zone
     
    Last edited: 10 Jun 2018
  8. Grumpy

    Grumpy Member

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    With regard to the comment re a bridge having an indeterminate life, presumably that life is estimated by bridge engineers together with the cost of maintaining the bridge until the time it has to be replaced. So if they stated that the bridge would have to be replaced in 10 years’ time then that cost, and any interim maintenance, would go into the DCF calculation as a credit. The cost to the project would thus be just the net present value of advancing the replacement. Every engineer I’ve ever dealt with on capital projects (outside railway) seemed to be adept at signing concurrences to this effect-if necessary with a pet external consultant to confirm matters.

    The comment re gauge clearing the route for new electric rolling stock was interesting. Perhaps the DfT should be issuing instructions that new rolling stock should be built to a gauge compatible with common existing stock.

    Line speed and frequency increases should presumably result in appropriate increased revenue estimates being inserted in the DCF statement to offset the cost. Again I’ve usually found there will be a senior marketing manager happy to provide a concurrence to such estimates. Particularly if he’s likely to retire in the period between the Business Case being made and the Post Implementation Review being completed-which might be several years.
     
  9. Joseph_Locke

    Joseph_Locke Established Member

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    I said interminable life - I don't think any bridge on any scheme has been imminently due for recon., but that might be because the asset owners have seen a funded project coming and identified a "budget opportunity". We do whole life costing (WLC) which attempts to quantify the maintenance savings associated with different reconstruction options, but as these are two different budgets (Project vs Maintenance) the Project can't actually bank the benefits.

    Oh for a standard vehicle gauge - and platforms that complied! However, recent projects have been clearing for 319, 321 and 323, none of which are exactly new.

    Yes, journey time improvements are benefits tested (well, they are when I do them) but the implementation works are still (generally) subject to a cost cap imposed fairly arbitrarily by others, so often the optimum BCR is not achieved.
     
  10. Tio Terry

    Tio Terry Member

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    You left out the effect on the railways neighbours. The EMC/EMI the railway exports and any EMC/EMI our neighbours may export to us, particularly under fault conditions. I seem to remember we had to take special measures for the feeder stations on HS1 - was it Singlewell and Sellinge? - where we had to avoid any metallic connection for the S&T circuits. Also, in the past, there were problems with Hospitals that were close to the railway and their rather delicate medical instruments as well as people with things like pacemakers fitted. The RSSB issued a Guidance Note, GL/GN1620, explaining what needs to be done.
     
  11. Joseph_Locke

    Joseph_Locke Established Member

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    Thanks for that one.
     
  12. Elecman

    Elecman Established Member

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    Or disconnect the DNO earth and use the Traction earth return, just don’t connect them together
     
  13. MarkyT

    MarkyT Established Member

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    Axle counters are a great help in helping to make S&T infrastructure compatible with electrification. Track circuits are by far the most problematic signalling sub system to accommodate alongside electrification as by their very nature they have at least one rail common with the traction return path for a single rail TC, or both rails in a double rail TC scenario. These rails cannot be earthed clearly, as desirable for safety, because that would permanently short out the TCs. For the double rail examples, expensive 'impedence bond' units at frequent intervals connect the rails to a separate parallel Earth conductor. Axle counters by contrast allow engineers to do away with all this complexity as their rail mounted sensors require no electrical commonality whatsoever with the traction system. Thus all the rails on parallel tracks can be periodically bonded together and with parallel Earth conductors wherever desired.
     
  14. Ships

    Ships Member

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    Yes but when the projects in their infoniin wisdom fit the cheaper kind it causes the other disciplines (PW in the main) other headache, like not being able to grind over them without taking the heads off...
     
  15. superkev

    superkev Member

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    I've always wondered if centres poles would be a better solution on double track sections. Half as many masts and less risk of damage to cables.
    Is there a clearance problem particularly now heads out of windows will soon become a thing of the past.
    K
     
  16. Ships

    Ships Member

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    You'd need larger 6fts for a start which can be an issue
     
  17. twpsaesneg

    twpsaesneg Member

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    The six foot (space between pairs of lines) isn't enough to accommodate in the vast majority of cases, the minimum clearance to steelwork without a specific risk assessment is 1624mm from each rail which means 3248mm rail to rail plus the steelwork size which is around 200-300mm for most cases.

    The vast majority of our network has nowhere near this much space.

    Even if you rewrote standards to go down to maximum Kinetic Envelope only you'd be struggling - I believe there's parts of the western where trains in theory collide due to sub standard 6's.
     
  18. superkev

    superkev Member

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    Interesting. So using a tamper to slew the tracks apart by the thickness of the mast say 100mm a track still wouldn't fit.
    K
     
  19. Tio Terry

    Tio Terry Member

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    There is often a surface water drain in the 6ft which would make creating able rather difficult and time consuming. Earthing cables, bearing in mind the need for a return conductor in the cable route, would have to pass under the running rails far more frequently causing tamping and track maintenance problems also.
     
  20. edwin_m

    edwin_m Veteran Member

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    The 6ft is the most dangerous place on the railway and needs tracks both sides closing if any work happens there, so better to minimise the amount of equipment to be maintained in that area.
     
  21. Joseph_Locke

    Joseph_Locke Established Member

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    Twin track cantilevers from one side achieve the same result without the astronomical cost of widening the six foot by at least 1.5m!
     
    Last edited: 14 Jun 2018 at 20:12
  22. Mordac

    Mordac Established Member

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    That's the 4ft, surely!:D
     
  23. corsaVXR

    corsaVXR Member

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    Depends if you're in the southern region or not...
     
  24. edwin_m

    edwin_m Veteran Member

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    Long time since I did a PTS course, but the logic is that in the 4ft you can only be hit by a train on one track, and there is probably a place of relative safety on one side or the other. In the 6ft you are in danger from either track with the possibility of trains approaching on both tracks simultaneously, in which case the stated course of action is to lie down and the unstated one probably to pray to your deity of choice and think about getting some new underwear.
     
  25. YorkshireBear

    YorkshireBear Established Member

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    There is often drainage in the cess which most electrification projects hit at some point....
     
  26. Class 170101

    Class 170101 Established Member

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    Any OLE work seems to need several tracks closing now. Two track railways see both isolated (and usually) closed. Four tracks require three to be isolated where work is required on the middle lines.
     

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