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Abellio Greater Anglia Class 755s (Regional Trains)

supervc-10

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From 25kV? That seems like quite the drop! I'm no electrical engineer but that must have caused some issues, even if it was limited to just a reduction in tractive ability.
 
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delticdave

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From 25kV? That seems like quite the drop! I'm no electrical engineer but that must have caused some issues, even if it was limited to just a reduction in tractive ability.

FWIW, all the original specifications for 25kV AC trains specified the performance requirements at 22.5 kV, rather than 25 kV.
Voltage drop is more common on lower voltage DC systems, the in-cab voltmeter showing 1100 volts in Dutch cabs wasn't unusual.
Over-voltage also happens, I've seen 3600 volts (rather than 3000 volts) in a Belgian MU cab standing in Luxembourg station, probably because there was no other train in the section.
 

dk1

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If you were inclined to guess a little further, do "supply issues" = voltage drop? I've been told, (by the electrification installation team at a Colchester open day) that when the Stowmarket feeder was offline the voltage in the area dropped to 16.5 kV, which wasn't such a problem back then. Today's electronically controlled rolling stock may not be so tolerant as 86's, etc.
Gosh that Stowmarket issue was a real pain. ETS was lost to the train as soon as acceleration from Stowmarket started & it was a slow old climb up Haughley Bank.
 

delticdave

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Gosh that Stowmarket issue was a real pain. ETS was lost to the train as soon as acceleration from Stowmarket started & it was a slow old climb up Haughley Bank.

I've a friend (retired Stratford driver.) who finished on 86's & Mk 2 driving trailers, I'll have to ask him for his thoughts re Stowmarket. It's possible that not many Norwich trains actually stopped there back in the early '90's.
 

dk1

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I've a friend (retired Stratford driver.) who finished on 86's & Mk 2 driving trailers, I'll have to ask him for his thoughts re Stowmarket. It's possible that not many Norwich trains actually stopped there back in the early '90's.
Almost all Norwich services called there following electrification in 87. The hourly Ipswich & Colchester only services where introduced around 2000 by Anglia. The issues with the feeder station where quite recent.
 

delticdave

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Almost all Norwich services called there following electrification in 87. The hourly Ipswich & Colchester only services where introduced around 2000 by Anglia. The issues with the feeder station where quite recent.

I've just checked the date of the respective Colchester Open day, it was 26-08-1991, so that's not really recent. The problem with Stowmarket feeder station back then was that it couldn't be used.
The quoted reason was that the single-phase load was too much for the local grid supply.
Perhaps, some 28 years later, that's no longer a problem.......
Q? What are / were the more recent issues?
 

dk1

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I've just checked the date of the respective Colchester Open day, it was 26-08-1991, so that's not really recent. The problem with Stowmarket feeder station back then was that it couldn't be used.
The quoted reason was that the single-phase load was too much for the local grid supply.
Perhaps, some 28 years later, that's no longer a problem.......
Q? What are / were the more recent issues?
Ah we are at crossed purposes. I was talking about last year when it went on for months & months. I wasnt driving that far back :lol:
 

hooverboy

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If you were inclined to guess a little further, do "supply issues" = voltage drop? I've been told, (by the electrification installation team at a Colchester open day) that when the Stowmarket feeder was offline the voltage in the area dropped to 16.5 kV, which wasn't such a problem back then. Today's electronically controlled rolling stock may not be so tolerant as 86's, etc.

the control electronics shouldn't be a problem.
the innards of the control system will be working at 12/24/48/110vdc and that should all be extremely well regulated.

the power electronics will be 750vdc, which might make things a bit slow off the mark if below that level.
I woluld have thought that 25KvAC stepped down to 800VAC, and then shoved through a (full wave)rectifier+capacitor bank and some zeners/shottkeys should be ample regulation to keep things stable in the event of a supply drop.
 

trebor79

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the control electronics shouldn't be a problem.
the innards of the control system will be working at 12/24/48/110vdc and that should all be extremely well regulated.

the power electronics will be 750vdc, which might make things a bit slow off the mark if below that level.
I woluld have thought that 25KvAC stepped down to 800VAC, and then shoved through a (full wave)rectifier+capacitor bank and some zeners/shottkeys should be ample regulation to keep things stable in the event of a supply drop.
That's all true but surely there must be some sort of power reduction if the line voltage drops significantly. Otherwise you'll draw a correspondingly larger current from the overhead, and possibly cause damage or failure of the pantograph, wiring from panto to transformer, or the components connecting the overhead to the grid.
 

fat_boy_pete

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Another 745/0 delivery just passed through Colchester. As NNR is apparently full and Crown Point bursting at the seams, where will it stable?
 

TheDavibob

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10 Oct 2016
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A follow up to my post yesterday, stop boards/changeover boards on Platform 1 at Cambridge North (southbound). No changeover boards obvious anywhere else (either end of the bidi(?) Platform 2, and I can't see the stop boards on P3 from here).
 

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class387

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Is the 755 to Cambridge running today?

Also, is the short set out today?
 

twpsaesneg

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21 Jul 2009
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the control electronics shouldn't be a problem.
the innards of the control system will be working at 12/24/48/110vdc and that should all be extremely well regulated.

the power electronics will be 750vdc, which might make things a bit slow off the mark if below that level.
I woluld have thought that 25KvAC stepped down to 800VAC, and then shoved through a (full wave)rectifier+capacitor bank and some zeners/shottkeys should be ample regulation to keep things stable in the event of a supply drop.
Conscious this is well off-topic, however with the BR-Era stock undervoltages would effectively just make things slower, as has been said. With more modern stock the issue that occurs / has occurred in the past is that the TMS sees a line voltage below the lower threshold cut-off and has a "computer says no" moment and shuts the unit down.
The other issue with drawing more power generally is that all of the grid points have an agreed capacity with the DNO (Domestic Network Operator) and drawing more than the agreed limit gets you penalised and also has knock-on effects for the grid generally. The railway has done this quite a bit - for instance Bow Feeder was for many years feeding well over agreed capacity - but it's something that people are keen to avoid.
 

twpsaesneg

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A follow up to my post yesterday, stop boards/changeover boards on Platform 1 at Cambridge North (southbound). No changeover boards obvious anywhere else (either end of the bidi(?) Platform 2, and I can't see the stop boards on P3 from here).
Passive provision for the reopening of the St. Ives branch? :D
 

themiller

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Conscious this is well off-topic, however with the BR-Era stock undervoltages would effectively just make things slower, as has been said. With more modern stock the issue that occurs / has occurred in the past is that the TMS sees a line voltage below the lower threshold cut-off and has a "computer says no" moment and shuts the unit down.
The other issue with drawing more power generally is that all of the grid points have an agreed capacity with the DNO (Domestic Network Operator) and drawing more than the agreed limit gets you penalised and also has knock-on effects for the grid generally. The railway has done this quite a bit - for instance Bow Feeder was for many years feeding well over agreed capacity - but it's something that people are keen to avoid.
All locos and emus have a nominal voltage but also a tolerance band within which they’ve been designed to operate. I can’t find the info at the moment but I seem to remember the class 92 being OK down to about 16.5kv!
 

delticdave

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All locos and emus have a nominal voltage but also a tolerance band within which they’ve been designed to operate. I can’t find the info at the moment but I seem to remember the class 92 being OK down to about 16.5kv!

Even more off-topic, Belgian loco's & EMU's (3.0kV DC) have been operating into Rosendaal & Maastricht (NL) under 1.5kV DC wires for many years. But, it seems that some of their new EMU's can't cope with 1/2 voltage which has resulted in the Maastricht - Liege service is now operated by ancient 1970's EMU's which really should have been scrapped!
It was noticeable that the acceleration rate improved after crossing the Belgian border.......
 

aswilliamsuk

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10 Jul 2016
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@delticdave the AM08 (Desiros) are mostly 3.0kV only, but some are 3.0kV/25kV. I thought that you'd need dual 1.5kV/3.0kV units to work that route - I can't recall if the AM62 group are dual voltage or not.

With the large number of new generation IC 'decker carriages coming I'd suspect that cascades will get shot of those AM62s soon enough!

(Anyway, back on topic, there was one of the new 755s parked up at Cambridge yard, near to the Newmarket route junction, when I passed through heading toward Ely on Monday morning).
 

fat_boy_pete

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Another 745/0 delivery just passed through Colchester. As NNR is apparently full and Crown Point bursting at the seams, where will it stable?
Anyone know where it went after Crown point? Or is it still there? Now at least 5 x 745's needing 1.25km of siding space!
 

LAX54

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Did hear a rumour the 745's may have same OHL issues that the other 700's have, ? as was shown last Friday when they all 'stopped' at the same time
 

ashkeba

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Did hear a rumour the 745's may have same OHL issues that the other 700's have, ? as was shown last Friday when they all 'stopped' at the same time
That seems rather surprising. Are Stadler using any Siemens suppliers?
 

LAX54

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That seems rather surprising. Are Stadler using any Siemens suppliers?
might be unconnected of course, you know what rumours are like ! but it does seem the 745's are not happy when the voltage drops
 

ashkeba

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might be unconnected of course, you know what rumours are like ! but it does seem the 745's are not happy when the voltage drops
Sounds unconnected because last Friday was reportedly mainly due to a frequency drop. Also 745 are Stadler, 700 Siemens, 710 Bombardier... seems unlikely that the same fault would afflict all unites numbered in 700s. But I guess time will tell. At least maybe 745s can be reprogrammed before entering service to avoid sitting down permanently.
 

hwl

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Sounds unconnected because last Friday was reportedly mainly due to a frequency drop. Also 745 are Stadler, 700 Siemens, 710 Bombardier... seems unlikely that the same fault would afflict all unites numbered in 700s. But I guess time will tell. At least maybe 745s can be reprogrammed before entering service to avoid sitting down permanently.
conspiracy theories galore...
With all the new train the TMS software is programmed with the "happy" voltage range and the units shut down outside that range. The 710s had a similar issue in late night testing as the voltage was no high as there were to few trains so the OHLE voltage was above the maximum permitted. (That particular supply is well known to be well above 30kV at night).

The Anglia region power supplies in (many) places are well known to be maxed out (i.e. North of Cambridge (cheap Kings Lynn spec in early 1990s minimal recent upgrades, no double 90s on GEML freights) and hence voltage will be very low in places but traditional stock is more tolerant as there isn't precision computer control enforcing shut down.

Correct under voltage shut down is actually a big electrical safety issue and far more complex than most would imagine as you ideally reduce traction power draw long before you reach thresholds. Hopefully Stadler have read the RSSB tomes...
 

bspahh

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The Anglia region power supplies in (many) places are well known to be maxed out (i.e. North of Cambridge (cheap Kings Lynn spec in early 1990s minimal recent upgrades, no double 90s on GEML freights) and hence voltage will be very low in places but traditional stock is more tolerant as there isn't precision computer control enforcing shut down.

There was a comment in a Network Rail delivery plan in January 2019 which said that the "West Anglia Outer" traction power upgrade was completed in November 2018. It was to increase the Firm Service Capacity at King’s Lynn to 3MVA.

It was on page 26 of the PDF that was available from https://cdn.networkrail.co.uk/wp-content/uploads/2019/01/EDP-December-2018.pdf However, that link is now dead.

Is there still a problem?
 

hwl

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There was a comment in a Network Rail delivery plan in January 2019 which said that the "West Anglia Outer" traction power upgrade was completed in November 2018. It was to increase the Firm Service Capacity at King’s Lynn to 3MVA.

It was on page 26 of the PDF that was available from https://cdn.networkrail.co.uk/wp-content/uploads/2019/01/EDP-December-2018.pdf However, that link is now dead.

Is there still a problem?
Yes - Only upgraded enough for GTR 8 car instead of 4 car to Kings Lynn etc. Stadler Bimodes not planned for...
 

ashkeba

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Yes - Only upgraded enough for GTR 8 car instead of 4 car to Kings Lynn etc. Stadler Bimodes not planned for...
I thought they were upgrading to be ready for half-hourly Kings Lynns both ways - but Ely North still prevents that so is there not some spare? But it sounds like another upgrade may be needed because of Abellio's bid - it is a shame coordination between infrastructure upgrades and service upgrades is not better.
 

hwl

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I thought they were upgrading to be ready for half-hourly Kings Lynns both ways - but Ely North still prevents that so is there not some spare? But it sounds like another upgrade may be needed because of Abellio's bid - it is a shame coordination between infrastructure upgrades and service upgrades is not better.
One bit of DfT not speaking to others.
 

dk1

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I thought they were upgrading to be ready for half-hourly Kings Lynns both ways - but Ely North still prevents that so is there not some spare? But it sounds like another upgrade may be needed because of Abellio's bid - it is a shame coordination between infrastructure upgrades and service upgrades is not better.
Not really because the forerunner to this already runs as far as Ely as an 8-car.
 

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