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Manchester - Liverpool Electrification
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HSTEd
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If you don't have some means of coupling the autotransformer centre taps together and for some reason rail continuity breaks due to a failed bond you could you potentially short the two feeders together and boom goes your autotransformer.
So I think this might just be a 0V conductor to ensure that the zero volt centre taps are all shorted together and thus stay at zero volts.
So I think this might just be a 0V conductor to ensure that the zero volt centre taps are all shorted together and thus stay at zero volts.
edwin_m
Veteran Member
I guess it's analogous to the neutral of a three-phase supply, which normally stays near earth potential but can go way off if there is a big load imbalance or one of the phases goes down. If there's any circumstance where large currents might flow through it then it needs to be insulated because it's a bad idea to have large currents flowing through the earth.
I think that it's insulated (say to 1kV) so that surges are controlled along the cable and not able to lift the voltage of local support hardware wrt the track. Don't forget that track circuits have isolation components, so bonding at every mast/portal would create disturbances in the track circuits.
Correct
--- old post above --- --- new post below ---
You don't have return conductor(rc) on a auto transformer system (atf), the extra wire on the side of the masts is an arieal earth. The main difference between the 2 system to tell them apart is the size of the insulator pots. RC pots are small single dish and usually bolted to the back of the mast/boom. The ATF one are 5/6 dish and mounted higher up on poles or dangling above high above the cantenary. The earth has no insulator and is bolted direct to the mast.
I'm still trying to get my head round how the ATF system works, even a trainer on a recent lineman course wasn't too sure. All I know is the ATF system alows more trains/electrical section than a RC system
There is a section in the old Electrification RUS (2009) that gives a reasonable explanation:
http://www.networkrail.co.uk/browse...ation strategy/networkrus_electrification.pdf
PDG1949
Member
Were the 319s just out of service equipped with 205 MHz NR VHF NRN (National Radio Network) radios or the UHF 450 MHz CSR ( Cab Secure Radio) system ? If the latter case it will require changing out to the new GSM-R Radio system and therefore this might be one of the Wolverton jobs?
Joseph_Locke
Established Member
*edit* covered in #2366 - should have scrolled up a bit further, but anyway:
(All text in quotes are descriptive but gross simplifications)
No, the ATF (or AF) is effectively the "negative" 25kV side of the system, where the OLE is the "positive" 25kV side and the rail is nominally the "zero". The autotransformer system keeps the "positive" 25kV side at 25kV by "borrowing" off the "negative" 25kV side by effectively shifting where "zero" is.
They may also be an earth wire, but this would be connected to the masts, not insulated from them. AF systems will also have a retrun screening conductor (RSC), but that lives in the cable rough, normally.
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Wow, thanks for that explanation. I had been planning a post on my blog for some time explaining the different electrification systems because I knew we were sometimes using the phrases "earth wire" and "return wire" wrongly.
I held off because I didn't know enough to write a proper explanation. Now you've covered it all clearly.
Thanks again.
Phil
The current (pun accidental) autotransformer discussion was started by #2350. Can somebody point us to some pictures of phase 1 where we can see the conductors in question and see whether they're connected directly to the masts or on small insulators?
This question is NOT about autotransformer feeds which we all know are on big insulators just like those used for the contact and catenary wires.
This question is NOT about autotransformer feeds which we all know are on big insulators just like those used for the contact and catenary wires.
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Class377/5
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The 319s were the first Thameslink units fitted with GSM-R.
steverailer
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On Phase 1 the earth wire is direct onto the mast not on an insulator. No pics, but know how it is because I fastened some of the bolts
Its a u shapped saddle bolted to the mast with 1 bolt and holds the wire in with 2 clamps and 4 bolts.
PDG1949
Member
Many thanks - was never quite sure which commuter trains down there were CSR or NRN. The Merseyrail electrics here are CSR and were apparently supposed to be one of the last to go over to GSM-R in these last few months.
Been mentioned previously but Allerton depot should be getting the juice back on this Sunday, also heard something about a neutral section getting put in too at Wavertree on the Chat Moss line, don't know how true this is, but the Slow lines at Edge Hill are de-wired at the moment. 221's are running in and out of Lime St for the first time in ages on Sunday as a result of the OHLE being off as mentioned elsewhere.
How about this for a neutral section!
[Youtube]q55EfuVYNW0[/Youtube]
Back in Manchester they were busy attaching the droppers and registration arms near to the station today but they are still short of the stanchions on the way into the station, not even any sign of the foundations on a couple.
[Youtube]q55EfuVYNW0[/Youtube]
Back in Manchester they were busy attaching the droppers and registration arms near to the station today but they are still short of the stanchions on the way into the station, not even any sign of the foundations on a couple.
GRALISTAIR
Established Member
Victoria I assume?
DJH1971
Established Member
PDG1949
Member
When putting in the metalwork west of Victoria, do they appear to have made any provision for the intended Ordsall Chord link-up ?
If I remember correctly, and if I observed correctly (I was actually trying to look while driving a car on Trinity Way), as you look along the viaduct going from Ordsall Lane Junction towards Salford Central, at the point where the Chord will begin to come in from the right, the supports switch to being cantilevers with supports on the left.
Now I think about it, I remember that the Chord plans in the first round of public consultation showed "proposed OHLE supports" and "existing OHLE supports" in that area. This was confusing as there were no supports in place at the time. I concluded that the supports shown as "existing" were the ones that it was originally proposed to put in, before the electrification design was changed to allow for the Chord.
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Ha, when you asked Victoria I was still in Australia thinking how clever, he knows what Australian State the air gap is in.
edwin_m
Veteran Member
It could be that some supports will turn out to be in the wrong places for the Chord, simply because the new viaduct is still being designed so nobody knows exactly where the OLE supports either need to go or are able to be supported by the new structure. So "existing" on that drawing could have meant "pre-existing" or "previously proposed". When different projects in the same place are authorised at different times, this sort of thing is likely to arise at the interfaces.
However the twin track cantilevers sound like the right way to go. Even if they need moving eventually, they should be able to keep the existing OLE operational while the Chord viaduct and junction are being built on the other side of the line.
However the twin track cantilevers sound like the right way to go. Even if they need moving eventually, they should be able to keep the existing OLE operational while the Chord viaduct and junction are being built on the other side of the line.
It's that expression again, just what does 'pre-existing' mean, (in the UK)?
edwin_m
Veteran Member
I take "pre-existing" to mean not necessarily existing at the time of producing a particular design drawing/document, but expected to be existing prior to whatever the drawing/document is seeking to change. Another useful one is that "removed" means that something is physically taken away, and "deleted" means it was previously intended to be installed but is now intended not to be installed.
The expression seems to be from the US and relates normally to insurance policy maschinations. The OED mentions it in that context only. What's wrong with previous(ly) or even prior, (depending on the grammar context?
This is not a whinge at you, just an observation about English usage and inheriting made-up wording that can confuse where words that we have been using for years can do the job.
hairyhandedfool
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ISTR hearing that some were put up in the wrong place.
In regards to my 'air-gap' link, its actually of trains in Queensland rather than Victoria
Here is a photo I took of the location of the future chord. As Snowball previously explained you will notice the metal work switching from one side to the other. All ready for the construction of the chord
As far as I know and the plans Ive seen the chord design is done, they just need the money and English heritage to get there arses in gear.
Here is a photo I took of the location of the future chord. As Snowball previously explained you will notice the metal work switching from one side to the other. All ready for the construction of the chord
As far as I know and the plans Ive seen the chord design is done, they just need the money and English heritage to get there arses in gear.
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