Dublin - Metrolink (Swords to Charlemont only)

L1011

https://www.boards.ie/discussion/comment/121941337#Comment_121941337

And it's over a hundred years old.

bk

https://www.boards.ie/discussion/comment/121941385#Comment_121941385

Go ahead explain why the Amsterdam Metro uses 750v DC

prunudo

Hows the Abp hearing going? Haven't seen much mention lately, has it wrapped up?

L1011

https://www.boards.ie/discussion/comment/121941395#Comment_121941395

Because it's also old.

It would be an absolutely appalling decision to make now.

Sam Russell

The use of 750 VDC would be compatible with existing Luas OH lines, making transition to GL much easier. If the connection could be maintained it would allow the stranded Luas trams at Sandiford to be moved back to city centre depots for maintenance.

What are the downsides to 750 VDC vs 1500 VDC? Is there any point in compatibility with DART vs Luas?

bk

https://www.boards.ie/discussion/comment/121941452#Comment_121941452

🙄 Latest line opened just 6 years ago!

L1011

https://www.boards.ie/discussion/comment/121941480#Comment_121941480

750V DC cannot supply as much overall power; and requires cables etc to be twice the size for the same amount of power. It would limit the performance of the trains significantly.

Stranded trams would be towed anyway, by virtue of being stranded, so would have their pantographs down and be de-energised.

Compatibility with DART is not a consideration due to different track gauge.

L1011

https://www.boards.ie/discussion/comment/121941490#Comment_121941490

First line began construction in 1970. That's the important date, unless you think that having lines that are incompatible by voltage alone is a good idea.

Its also third rail. Third rail is nearly always lower voltage for safety reasons; although realistically it should never be used on entirely new systems as its still not particularly safe! (and is also severely affected by weather, on overground sections)

CatInABox

https://www.boards.ie/discussion/comment/121941440#Comment_121941440

Hearings started back up yesterday, with all the residents committees around SSG and Charlemont/Dartmouth having their say. I can't find anything online about it, so it doesn't look like even the Irish Times are interested in their story.

Today, it's the OPW with an hour, the Rethink Metrolink crowd with their crayons, and a bunch of other people without a group/committee.

Overall, the hearings are going exceptionally well. There's been no problems raised that haven't been solved with a doc issued the next day.

tom1ie

https://www.boards.ie/discussion/comment/121941491#Comment_121941491

So would the 1500VDC referenced on the last page in that graphic be state of the art or would state of the are be 25kv AC?

What is HS2 using?

I suppose 25KVAC would have a massive power draw on the ESB system as they would have to supply at 38KV as opposed to the MV (10/20KV system).

prunudo

https://www.boards.ie/discussion/comment/121941518#Comment_121941518

Thank you, appreciate your daily reviews during the hearings.

L1011

https://www.boards.ie/discussion/comment/121941627#Comment_121941627

25kV AC would be rare for a metro (but it does exist), 1500V DC is the norm for new metro lines in Europe for the past ~20 years.

We're likely to have some 25kV AC eventually, it won't be 1500V DC Heuston-Cork whenever that is electrified for instance. The potential of 25kV AC is mentioned in the tender for new Enterprise units.

All completely new UK electrification is 25kV AC, so HS2 and Crossrail both use that. Extensions to the 750V DC (third rail) and 1500 DC (overhead) they have in patches does still happen.

tom1ie

https://www.boards.ie/discussion/comment/121941660#Comment_121941660

So to future proof metrolink we should really be looking at 1500VDC If not 25KVAC.

bk

https://www.boards.ie/discussion/comment/121941716#Comment_121941716

There isn't real anything about future proofing here.

Modern long distance services like intercity trains tend to use 25KVAC. Trams tend to be either 600V or 750V DC and Metro's can be anything from 400V DC to 3000V DC, with some AC too, but those tend to be longer distance services, more commuter like.

It really just depends on what the requirements of the system, substation, local grid, top speed, vehicle lengths, etc.

murphaph

https://www.boards.ie/discussion/comment/121941395#Comment_121941395

It's third rail like most or all of these heavy rail "low" voltage systems (like the LU, Berlin S-Bahn, Most German U-Bahns etc.). Third rail means you have a big fat conductor capable of delivering serious amps to the trains even at lower voltages, but also to any unfortunate person who might come into contact with that third rail. Overhead catenary systems providing power to heavy rail typically operate at higher voltages because of the reduced cross section of the conductor. Third rail is inherently more dangerous than OH, so OH should be preferred in any greenfield metro being built today. Once you are going OH the length if trains etc. is going to determine the required voltage. I very much doubt 750V would cut the mustard on a sytsem like Metrolink. You'd need more substations for sure than if you went with a more common 1500V supply.

KrisW1001

The metrolink green line update constructability report from 2019 makes mention of removing and reinstating the overhead electrical lines, but only because Luas uses higher lines than Metrolink... there was no mention of change of voltage or substations. That implies a plan, in 2019 at least, of using 750 V DC.

The original Metro North chose 750 V because it was planned to be interoperable with Luas trams in some areas. Actually, it was never even clear whether Metro West would use trams, or metro cars.. The new automatic Metrolink means that interoperability with Luas on the same lines is impossible.

Because it cannot share its tracks with any other service, Metrolink can use any kind of voltage it wants to, but DC operation is more suitable than AC for a short distance high-frequency service.

For starting from a clean slate, 1500 V would be a good choice, as it allows higher power transfer, which in turn means lower voltage drop along the suppy cables, which allows the substations powering the system to be further apart. As for risks, engineers here already have experience of how both 750 and 1500 perform in Irish conditions from Luas and DART, respectively..

tom1ie

https://www.boards.ie/discussion/comment/121942492#Comment_121942492

Just on this, are there any downsides to going with 1500VDC over 25KVAC?

KrisW1001

Not really. The big advantage of AC is that it's efficient for sending power over long distances. The downside is that AC power needs more complicated driving electronics in the train itself. That used to mean heavier equipment in each train, but I think with modern power electronics this isn't as big an issue as it was.

The reason most city "metro" services use DC is mainly that until the 1960s there was no efficient and lightweight way of controlling motor speed from a single-phase AC supply. By comparison, DC speed control was pretty easy. Metro trains need to accelerate very quickly, so smooth speed control is essential. Then, when AC speed control became easy and cheap, the need for compatibilty with existing infrastructure locked in the use of DC.

The downside of DC is that electrical generation is all AC, so you need to convert it to DC (rather than just stepping down the voltage). Plus, DC at lower voltages needs to be applied every 1km or so in the network, as the voltage will fall as you get further from the supply. AC can travel much further distances without voltage drops.

The general trend is for "mainline" and commuter rail to use AC, and metropolitan-area services to use DC. Some continental railways (e. g. Italy) that electrified relatively early also use DC for long distance services, but this is being migrated to AC.

The big negative of going with DC is that the rest of the railways in this country will be electrified at 22kV AC. But this does not matter, as it will be physically impossible to bring mainline trains on ML tracks. First, there's a different track gauge, and second, as an autonomous system, ML requires exclusive use of its tracks.

It's possible to set up dual or triple voltage supplies for trains, as will probably happen with some of the areas where DART+ services, at 1500 V, mix with mainline rail, planned for electrification at 22kV AC, but this can't happen on ML.

jd

Irish Times reporting that the public consultation will reopen

https://twitter.com/IrishTimes/status/1772706411056865544

L1011

https://www.boards.ie/discussion/comment/121942934#Comment_121942934

That's going to add months to the timeline even if ABP decide there's no need for hearings after submissions.

Tileman

Ffs delay things further but I suppose it reduces chance of judicial review by certain applicants.

cgcsb

I was optimistic but with this news I think the project is toast. Whatever garbage idea of opening a 6th round of pc at the stage is about it'll certainly push a construction start beyond the life of this government so its done for, what a waste.

prunudo

The whole procedure and process to planning and building major infrastructure needs to be streamlined. Its beyond a joke how long projects are taking these days.

loco_scolo

TII have said they welcomed the decision. Surely then, it must have been expected and planned?

Given how smoothly the hearings have gone so far, and how quick TII have been to produce updates docs etc., I wouldn't get too pessimistic just yet.

Zebra3

Why would anyone who actually wants this built welcome this decision?

L1011

https://www.boards.ie/discussion/comment/121943229#Comment_121943229

A public consultation takes time - considerable time - you can't just make it quicker.

cgcsb

It's as irregular as it is frustrating, this is not how the, albeit broken, planning system works, you don't go from statutory consultation back to public consultation. That means re submitting surely? Does anyone have access to the article?

Hibernicis

Does anyone have access to the article?

Yup.

Basically TII has submitted a lot of additional documents. ABP believes that additional public consultation is warranted. TII taking it on the chin and doing what they very competently do and taking it in their stride.

Main point of concern in the article is this:

Speaking before the hearing started, Minister for Transport Eamon Ryan said he was confident the board would issue its decision on MetroLink by the end of this year. 

With that fool's track record, such an assurance has to be an ill omen.

Anyway, this is a mere hiccup. There is still a reasonable chance that construction will commence before the end of the decade.

cgcsb

https://www.boards.ie/discussion/comment/121943495#Comment_121943495

But surely this means this ro is cancelled and they have to resubmit?

L1011

https://www.boards.ie/discussion/comment/121943526#Comment_121943526

Standard planning procedures allow for re-advertising when there is significant further info; without having to restart from scratch. I presume this is basically the same

Yellow site notices in normal planning are FI (or very quick resubmissions I think also); you see piles of these.