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Post by phil on May 4, 2019 15:32:19 GMT
- Reduction in the risk of motor flashover at high speed with weak field, especially on the now 750V supplied parts of the Met line. Seems uneccessary given that D stock ran happliy for many years on Network Rail metals supplied at 750v.
But did they?
When the LSWR started its 3rd rail electrification programme it used a nominal 630V DC (the same as the Underground). This voltage was continued by the newly formed Southern Railway for all subsequent electrification projects up until the electrification of the Brighton Main Line south of Coulsdon where an increased voltage of 750V was used. However no changes were made to the already installed 630V suburban areas as the rolling stock used on said routes would have expensive requited modifications to cope with the higher voltage.
Similarly when the LNWR started electrifying the North London line, they stuck to 630V and BR saw no reason to change this
While BR(Southern) did eventually instigate a programme of upping the voltage in suburban areas this had to wait until the 630V stock had all been replaced - indeed central division routes from Victoria / London Bridge to Coulsdon had to stay at 630V right up until the early 1980s when the last of the 630V rated 4SUB units were withdrawn.
Therefore given the areas where district line trains shared tracks with BR 3rd rail stock were all originally energised at 630V its entirely possible that they remain so to this day. << Londonstuff: Thread split from here when resulting conversation started to talk about voltages. This post was moved from here.>> |
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Colin
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Post by Colin on May 4, 2019 15:40:05 GMT
The inner sections of the South Western division have historically been fed at 660V DC, because of the presence of LU trains But did they? When the LSWR started its 3rd rail electrification programme it used a nominal 630V DC (the same as the Underground). [snip] Therefore given the areas where district line trains shared tracks with BR 3rd rail stock were all originally energised at 630V its entirely possible that they remain so to this day. Well my original Network Rail training 15 years ago, and annual Network Rail refresher every year since has only ever mentioned 750v DC or 25,500v AC. What you are both saying is news to me and every other Network Rail trained driver on London Underground! |
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Post by t697 on May 4, 2019 16:30:36 GMT
I seem to recall the inner sections were around nominal 660V and measurements of around 700V at Wimbledon on old LUL trains some years ago. I think it has now been raised and of course both LUL S stock and other modern trains on the NR tracks have Regen braking pushing the voltage up to about 900V or just under.
The RAT train has had some modifications to keep it running OK with these voltages, regular D stocks didn't.
Probably training standardised on a nominal 750V DC for simplicity.
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North End
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Post by North End on May 4, 2019 18:35:30 GMT
The inner sections of the South Western division have historically been fed at 660V DC, because of the presence of LU trains But did they? When the LSWR started its 3rd rail electrification programme it used a nominal 630V DC (the same as the Underground). [snip] Therefore given the areas where district line trains shared tracks with BR 3rd rail stock were all originally energised at 630V its entirely possible that they remain so to this day. Well my original Network Rail training 15 years ago, and annual Network Rail refresher every year since has only ever mentioned 750v DC or 25,500v AC. What you are both saying is news to me and every other Network Rail trained driver on London Underground! I wouldn’t necessarily believe everything that comes out of Ashfield House! There’s certainly things which are out of date, factually dubious, or dumbed down for operational purposes where people don’t *need* to know the finer details to simply be the end user of a system. I wonder if they still train that draw-up signals show a dual aspect whilst the train’s speed is being measured?! Likewise with TBTC the trains training refers to VOBCs as halted, ready and communicating, yet more technical staff (including service control) refer to halted, dormant, passive and active. As regards the 660V DC, there’s a limited amount available on the internet which sheds a little more light on this. I’m not sure where things are at now, however it was definitely the case 5 or so years ago that the inner areas had the lower voltage. |
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Tom
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Post by Tom on May 4, 2019 19:12:25 GMT
I wonder if they still train that draw-up signals show a dual aspect whilst the train’s speed is being measured? Bar a handful of examples where the mechanism of the time delay caused this as a side effect, and one particular occurrence when it was done to give drivers confidence that the signal had cleared, it was never the case. |
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Tom
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Post by Tom on May 4, 2019 19:13:39 GMT
Well my original Network Rail training 15 years ago, and annual Network Rail refresher every year since has only ever mentioned 750v DC or 25,500v AC. I've only ever been taught 25,000v, are you sure? |
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North End
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Post by North End on May 4, 2019 19:38:27 GMT
I wonder if they still train that draw-up signals show a dual aspect whilst the train’s speed is being measured? Bar a handful of examples where the mechanism of the time delay caused this as a side effect, and one particular occurrence when it was done to give drivers confidence that the signal had cleared, it was never the case. Another little Ashfield House irritant was being told in CDP that any signal number which starts with an A is an automatic signal. When it was pointed out that the Northern Line (at the time) had semi-automatic cabin codes startinf with A as in AC and AE they wouldn’t have it until specific evidence was provided, and even then they insisted upon checking with the SOM that the signals themselves weren’t actually autos. Then there was the S signals with their supposedly “special” relays. Meanwhile, during one of their exercises they had one involving opening a section switch. I forget the exact details, but it was pointed out that the section switches concerned were not in the place they thought they were (to be fair, the TCDs were presented in a slightly misleading though technically accurate way), and that opening these switches would not have achieved the desired result. I can understand when they simplify things when people don’t really need to know the finer details, although I’m still not entirely comfortable with people being ingrained with something which isn’t so in reality as they may well in the future move to a role where the difference *does* matter, but there’s no excuse for stuff which is simply plain wrong. Not sure if they still teach about the draw-up signals, someone who has been through recently would have to comment on that! |
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Deleted
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Post by Deleted on May 4, 2019 21:03:01 GMT
S Signals were Auto's on the southern part of the Northern Line and in the signalling alphabet Z is special not S
Back to the original topic please we are drifting
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Post by phil on May 6, 2019 23:31:33 GMT
The inner sections of the South Western division have historically been fed at 660V DC, because of the presence of LU trains But did they? When the LSWR started its 3rd rail electrification programme it used a nominal 630V DC (the same as the Underground). [snip] Therefore given the areas where district line trains shared tracks with BR 3rd rail stock were all originally energised at 630V its entirely possible that they remain so to this day. Well my original Network Rail training 15 years ago, and annual Network Rail refresher every year since has only ever mentioned 750v DC or 25,500v AC. What you are both saying is news to me and every other Network Rail trained driver on London Underground! From a safety perspective a 630V electric shock will do you the same amount of damage as a 750v one. The same applies as regards, say infrastructure damage through incorrect isolations or debris causing a flashover between the 3rd and running rails.
As such it makes sense to keep things simple and only use the 750V figure (which is after all only a nominal one as under certain conditions the actual voltage can drift quit a bit higher) - especially as London Underground have the long term goal of upping their traction voltage to this figure over time.
Also, given all British Rail designed stock (and everything built after privatisation of course) is quite capable of running at 750V, plus the fact that most of the BR(S) 3rd rail network required significant upgrades over a decade ago to cope with the withdrawal of the slam door fleet, then its quite possible that the only bits of the 3rd rail network not using 750V are the tiny bits still used by LU (which I'm sure will be upgraded in due course to 750V now the S stock is in service) so its hardly surprising they might have flown under the radar as it were in training terms.
However it cannot be denied that back in the 1970s, the 630V legacy of the LSWRs early electrification schemes was very real in suburban London - and as such LU stock would not have been subjected to higher voltages on lines shared with British Rail 3rd rail services.
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Ben
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Post by Ben on May 7, 2019 3:31:40 GMT
The inner sections of the South Western division have historically been fed at 660V DC, because of the presence of LU trains But did they? When the LSWR started its 3rd rail electrification programme it used a nominal 630V DC (the same as the Underground). [snip] Therefore given the areas where district line trains shared tracks with BR 3rd rail stock were all originally energised at 630V its entirely possible that they remain so to this day. Well my original Network Rail training 15 years ago, and annual Network Rail refresher every year since has only ever mentioned 750v DC or 25,500v AC. What you are both saying is news to me... C and D stocks have run on both LU and NR metals all their lives, with the associated varying voltages - so why would the Picc's 73ts suddenly have an issue?!! In those areas where C and D operate the NR supply voltage is dropped from the nominal 750 V to (I think) 630 V. On NR adjacent sections to where 630 V is necessary there are voltage step sections of another voltage between 750 V and 630 V either to ensure smooth transitions. In the RT/NR SR zone power reinforcement project of the early 2000s to cater for AC motor units like Desiros and Electrostars there is provision to step up those section to 750 V once the older LU stock types have gone. BTW, SR zone third rail main line train performance calculation and all continuous electrical ratings are all at 675 V not 750 V - the latter is actually the one hour rating. (and 25 kV OLE is really 22.5 kV for equivalent discussions). "spotting" books like the old IA ABC and present day P5 books ignore this fact - the power and so on figures given are not 750/25000 V but 675/22500 V ... tis is easily proved by looking at was used to be called the "BR Diagram Book". Not sure how true that is. SS had the same generic 339 traction motor type as 4Sub units did. At the time 4Subs were in traffic, they themselves as 660 V units had restrictions on where they could go in "country" 750 V areas. Now all thats 30 years ago, it is possible SS has had rewound motors, it is normal practice these days to wind motors to the highest insulation standards which easily handle something like 630 to 750 V. AIUI this also applies to C and D stock, they are all old enough that their motors at some point in their lives will have had a major overhaul and possibly a rewind ... I don't know what LU does in this respect, but certainly BR SR did this. The question will be, has SS had such work on it ? The motors on batteries are even older. yes they did work to Streatham Hill etc, but that was still a lower voltage suburban area at the time they did that. Bet we won't ever see that again. -- Nick |
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Post by stapler on May 7, 2019 6:52:13 GMT
Sorry to be technically illiterate.
What would happen if you ran a train with motors designed for 630V on a 750 supply?
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Post by norbitonflyer on May 7, 2019 7:04:37 GMT
its quite possible that the only bits of the 3rd rail network not using 750V are the tiny bits still used by LU (which I'm sure will be upgraded in due course to 750V now the S stock is in service) Not forgetting the sections used by the 1972 tube stock Sorry to be technically illiterate. What would happen if you ran a train with motors designed for 630V on a 750 supply? On older trains, nothing much - they might even be able to go a bit faster. There would be potential problems if electronic circuits couldn't cope with the higher voltages without overheating and, in particular, whether the electrical insulation on the internal wiring was up to the job. |
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Post by phil on May 7, 2019 10:34:00 GMT
Sorry to be technically illiterate. What would happen if you ran a train with motors designed for 630V on a 750 supply? If the wiring insulation is not good enough then you can get short circuits, overheating and things going bang!
If basic electrical components are only rated for 630V then working at a higher rating may cause problems with arc damage or premature wear taking place going rise to more frequent failures.
If complicated electronics are involved then overvoltage is likely to trigger either an automatic shutdown or terminal damage as soon as it happens.
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Post by londonstuff on May 7, 2019 13:03:03 GMT
Admin comment
The thread has continued to go off track so I've moved some posts across to a new thread - Voltages across the System, linking both threads to each other by adding to the first/last comment in each thread.
I've done this pretty quickly so some other members of staff might move some other posts across to a more appropriate place imminently.
In this thread, please continute to discuss voltages, in the other, let's stick to Vivarail.
Ta, all. 
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Post by superteacher on May 7, 2019 17:21:20 GMT
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Colin
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Post by Colin on May 7, 2019 19:13:14 GMT
Well my original Network Rail training 15 years ago, and annual Network Rail refresher every year since has only ever mentioned 750v DC or 25,500v AC. What you are both saying is news to me and every other Network Rail trained driver on London Underground! I wouldn’t necessarily believe everything that comes out of Ashfield House! Whilst Network Rail training is delivered by Skill's Development trainers (or whatever they're called this week), to be clear they are not cherry picking the information they deliver. They deliver what is contained in the RSSB working over books - the rule books that are created for Network Rail and which Network Rail nationwide work to. It is wrong to state that LU or its trainers have had any hand in the content delivered in relation to Network Rail rules & procedures to Bakerloo and District line drivers. Likewise with TBTC the trains training refers to VOBCs as halted, ready and communicating, yet more technical staff (including service control) refer to halted, dormant, passive and active. They have perhaps learned from TBTC as the training for CBTC uses the terms halted, communicating, active and passive. Well my original Network Rail training 15 years ago, and annual Network Rail refresher every year since has only ever mentioned 750v DC or 25,500v AC. I've only ever been taught 25,000v, are you sure? Yep, my original post should have said 25,000 - I must have been trigger happy with the '5' key when I typed it  |
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Post by t697 on May 7, 2019 19:17:00 GMT
Sorry to be technically illiterate. What would happen if you ran a train with motors designed for 630V on a 750 supply? I see there are several answers about motoring performance already. On a typical older LUL train, yes it will go faster. The resistor grading on notches won't be ideal and the transition from Series to Parallel notching won't be as smooth.
But don't forget there are several auxiliaries fed from the traction supply. On a typical older LUL train; Motor Alternators to provide low voltage supplies and battery charging, Air compressors, Saloon and Cab heaters, Retrofitted Static Inverter to power cab air cooling. 1973TS and 1972TS have not had some or all of these systems made suitable for extended operation on 750V/890V. |
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Post by norbitonflyer on May 7, 2019 21:43:32 GMT
But don't forget there are several auxiliaries fed from the traction supply. On a typical older LUL train; Motor Alternators to provide low voltage supplies and battery charging, Air compressors, Saloon and Cab heaters, Retrofitted Static Inverter to power cab air cooling. 1973TS and 1972TS have not had some or all of these systems made suitable for extended operation on 750V/890V. For the same reason, I read that Southern 4SUB stock, if straying west of Woking for any reason, used to have to have certain circuits disconnected as the 1967 extension of electrification beyond Woking to Bournemouth was at 750V and the SUBs were only rated for 630V |
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North End
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Post by North End on May 7, 2019 22:48:07 GMT
Whilst Network Rail training is delivered by Skill's Development trainers (or whatever they're called this week), to be clear they are not cherry picking the information they deliver. They deliver what is contained in the RSSB working over books - the rule books that are created for Network Rail and which Network Rail nationwide work to. It is wrong to state that LU or its trainers have had any hand in the content delivered in relation to Network Rail rules & procedures to Bakerloo and District line drivers. In all honesty, I wouldn’t really expect OL to pay much attention to the finer details. It’s a quirk which isn’t particularly well known about, and doesn’t have any impact on operating staff in the course of their duties. So long as train staff appreciate that “750V DC” is the equivalent of LU’s 630V DC supply and there’s no scope for confusing 630V train equipment with other voltage circuits/equipment then there’s no real issue. In the same way that “750V DC” can actually mean something else elsewhere on NR too - IIRC the Pirbright-Bournemouth electrification scheme is or was one such area, in this case the nominal voltage being a nominal 850V DC in some areas at least, which IIRC allowed the substation spacing to be extended as an economy measure. To be fair, I’ve only heard the 660V DC referenced by two rather obscure albeit reliable sources. Once in a talk I attended some years ago delivered by a senior NR electrification design engineer at the time of the upgrades for slam-door replacement, and rather more recently in various NR and LU documentation which refers to a NR-led project to separate off LU supplies. As it doesn't affect operating staff, there's no need for it to be more widely documented. Needless to say from an electrification engineering point of view the difference will have more importance. They have perhaps learned from TBTC as the training for CBTC uses the terms halted, communicating, active and passive. Does this imply trains are always in communication with the system, even if inside an unsignalled depot? With the looped based system they lose communication as soon as the train goes off the inductive cable, which in reality is Morden, Edgware, Highgate, Golders Green, Neasden or Stratford Market depots (or during a loop failure). |
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Post by superteacher on May 8, 2019 19:07:35 GMT
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Post by trt on May 9, 2019 15:56:04 GMT
I suppose if you're talking about signalling and voltages, there is a potential difference to flag up.
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class411
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Post by class411 on May 9, 2019 16:17:02 GMT
I suppose if you're talking about signalling and voltages, there is a potential difference to flag up. The mods have the capacity to object to such differences and have a resistance to having them in a thread. It can often induce them to split such a thread. I oscillated in deciding whether to amplify my thoughts on that theme with a battery of observations in parallel with a series of facts, but realised it would take the thread quite off topic. |
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Post by superteacher on May 9, 2019 18:31:32 GMT
Amusing, but this next comment should not be too much of a shock:
Back on topic please.
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Post by brigham on May 10, 2019 7:36:52 GMT
Through trains from the Liverpool Overhead Railway to Aintree on race-days were restricted to the series-notches only, because of the higher voltage on the Lancs & Yorks section.
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class411
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Post by class411 on May 10, 2019 9:14:53 GMT
Does anyone know if all current (well, built within the last 20 years, say) third rail stock - under and over ground - have 'intelligent' power systems that can handle varying voltages, and what the limits of these voltages are?
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Post by phil on May 10, 2019 18:33:09 GMT
Does anyone know if all current (well, built within the last 20 years, say) third rail stock - under and over ground - have 'intelligent' power systems that can handle varying voltages, and what the limits of these voltages are? Given every train produced over the past 20 years uses AC traction motors and complex control systems, dealing with under or over voltage is easy. Basically the various rectifiers and semiconductor technology necessary to generate a nice pure AC voltage for the motors will prevent over or under voltage causing problems / being passed on to the motors etc unless it gets to extreme levels. The problem with earlier stock is precisely because there was no voltage processing going on - what came off the conductor rails was fed directly into the control (or indeed carriage lighting circuits - pre 1950s build BR stock lacked batteries to keep them going if the con rail got turned off so had to keep on using oil tail lamps instead of two red blanks). If you are using basic ohms law and switching resistances in / out to control motor speed then a small change in conductor rail voltage will have a direct effect on the voltages passing through critical components. |
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roythebus
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Post by roythebus on May 11, 2019 21:20:46 GMT
Several misconceptions on this thread. The difference between NR/BR and LT power supplies was made by means of neatral or dead sections, these being on Putney Bridge and between Gunnersbury and Trunham Green on the District. I'm not sure how this was dealt with on the Bakerloo at queens Park as I never worked that line. The dead sections on the dR were long enough to "gap" a stalled train and long jumper eads had to be used to get a gapped train moving. I can't comment on what system they use these days.
On the older SR stock, SUBs and BILs that lingered they would run a bit faster on the highter voltage sections. Lights were wired in series and could easily blow if subject to much higher volts, so lights had to turned off south of Brookwood on the LSWR main line. However, that wouldn't stop surges to higher voltages in the low voltage sections as trains passed from one substation to another.
455 stock used 2nd (or 3rd) hand SUB motors and these were ok working at the higher voltages. They also used SUB compressors quite happily. Control circuits on the BR slam-door stock was generally 110v or lower with power supplied by the motor generator sets or back-up batteries.
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metman
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Post by metman on May 12, 2019 9:34:13 GMT
Staying on the LU/NR interface I wonder what mitigation there is on the 1972 stock (if any) where the negative rail is bonded to the running rails?
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Post by goldenarrow on May 12, 2019 16:09:46 GMT
roythebus , Going Northbound through North shed there is a substantial section gap (comparable to Putney Bridge) at signal WS 13. Going South, signal WS 8 has an LU style section gap indicator with the gap itself which IRRC is over the trap points.
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Post by phil on May 12, 2019 18:00:44 GMT
455 stock used 2nd (or 3rd) hand SUB motors and these were ok working at the higher voltages. They also used SUB compressors quite happily. Its extremely unlikely said motors etc. were simply transferred from the Subs to the 455s - they almost certainly were rewound / overhauled first. this would have provided the opportunity to upgrade things like the varnish / wire used in the windings to handle higher voltages and allow an increase in conductor rail voltage compared to their 'as built' state.
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