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Upgrading sub surface tube lines to 750V
I read about this in wikipedia but is it actually going to happen? If so what
will happen on sections where tube and sub surface stock run on the same track - ie raynors lane to uxbridge and acton town to ealing common. Will these sections be kept at 630V or will the piccadilly stock be able to handle 750V anyway? B2003 |
Upgrading sub surface tube lines to 750V
d wrote:
I read about this in wikipedia but is it actually going to happen? If so what will happen on sections where tube and sub surface stock run on the same track - ie raynors lane to uxbridge and acton town to ealing common. Will these sections be kept at 630V or will the piccadilly stock be able to handle 750V anyway? There is definitely a power supply upgrade going on, just announced he http://www.tfl.gov.uk/corporate/medi...tre/15249.aspx but they don't explicitly say they are raising the system voltages - it wouldn't necessarily follow anyway, the regulated voltage could stay the same but with a higher current draw being allowed. Related to this, there are apparently Network Rail projects going on at the moment to separate out all the mainline and 'tube' supplies where they are connected, to allow the NR third rail voltage to be raised to a standard 750 volts, and to allow regenerative braking. An example is the Waterloo and City, still fed off the SR for obvious historic reasons. What I'm wondering is that if LU adopted a 750 volt standard on the SSR, NR wouldn't necessarily need to do this - unless they want to have separate billing anyway - there's also practicalities such as isolations for maintenance. Paul S |
Upgrading sub surface tube lines to 750V
On Mon, 12 Apr 2010 14:50:26 +0100
"Paul Scott" wrote: http://www.tfl.gov.uk/corporate/medi...tre/15249.aspx but they don't explicitly say they are raising the system voltages - it wouldn't necessarily follow anyway, the regulated voltage could stay the same but with a higher current draw being allowed. Raising the voltage does seem an odd thing to do not least because they dropped the voltage from 640V years ago citing power saving reasons (which sounds like rubbish TBH , lower voltages are less efficient , not more). B2003 |
Upgrading sub surface tube lines to 750V
"Paul Scott" wrote in message
... d wrote: I read about this in wikipedia but is it actually going to happen? If so what will happen on sections where tube and sub surface stock run on the same track - ie raynors lane to uxbridge and acton town to ealing common. Will these sections be kept at 630V or will the piccadilly stock be able to handle 750V anyway? There is definitely a power supply upgrade going on, just announced he http://www.tfl.gov.uk/corporate/medi...tre/15249.aspx but they don't explicitly say they are raising the system voltages - it wouldn't necessarily follow anyway, the regulated voltage could stay the same but with a higher current draw being allowed. Related to this, there are apparently Network Rail projects going on at the moment to separate out all the mainline and 'tube' supplies where they are connected, to allow the NR third rail voltage to be raised to a standard 750 volts, and to allow regenerative braking. An example is the Waterloo and City, still fed off the SR for obvious historic reasons. What I'm wondering is that if LU adopted a 750 volt standard on the SSR, NR wouldn't necessarily need to do this - unless they want to have separate billing anyway - there's also practicalities such as isolations for maintenance. Paul S The Central Line is already 750V - it was converted with the last upgrade. There is still a difference between nominal voltages on LUL (4 rail) & NR (3 rail). Peter -- Peter & Elizabeth Corser Leighton Buzzard, UK |
Upgrading sub surface tube lines to 750V
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Upgrading sub surface tube lines to 750V
On Mon, 12 Apr 2010 14:57:36 +0100
"Peter Corser" wrote: The Central Line is already 750V - it was converted with the last upgrade. Does that mean the western central line can't be used for stock moves any more except for 92 stock? B2003 |
Upgrading sub surface tube lines to 750V
Basil Jet wrote:
On 12/04/2010 14:56, d wrote: Raising the voltage does seem an odd thing to do not least because they dropped the voltage from 640V years ago citing power saving reasons (which sounds like rubbish TBH , lower voltages are less efficient , not more). ... unless the lower voltages leak less. Lower voltage means a higher current draw for the same power, and transmission losses are proportional to I^2. Rgds Denis McMahon |
Upgrading sub surface tube lines to 750V
On 12 Apr, 15:28, wrote:
On Mon, 12 Apr 2010 14:57:36 +0100 "Peter Corser" wrote: The Central Line is already 750V - it was converted with the last upgrade. Does that mean the western central line can't be used for stock moves any more except for 92 stock? B2003 Doesn't Bakerloo tube stock run on 750 V beyond Queens Park? |
Upgrading sub surface tube lines to 750V
On Apr 12, 2:33*pm, wrote:
I read about this in wikipedia but is it actually going to happen? If so what will happen on sections where tube and sub surface stock run on the same track *- ie raynors lane to uxbridge and acton town to ealing common. Will these sections be kept at 630V or will the piccadilly stock be able to handle 750V anyway? B2003 The issue on LUL is that at a nominal voltage of 750 V, the maximum voltage that could be seen at the train could be 900 V (under light loading conditions) and equipment in some of the older stock could be vulnerable to damage at such a voltage (eg by flashover). This particularly applies to starting resistances. It is for this reason that the Southern's line voltage is kept to 660 V in the inner suburban area (to about 15 miles from London, plus branches like Tattenham Corner and Epsom Downs), owing to the interfaces at Waterloo (W&C), East Putney, Wimbledon, Gunnersbury and Richmond, and the complexity of the inner suburban network. (Although not used by Southern trains, the Richmond - Gunnersbury section is part of the SR electrification system and is separated from the NLL system at Gunnersbury Junction by a gap in the con-rail. A similar gap also exists on the District Line.) The line voltage is graded upwards outside the suburban area; on the Brighton Line, for example, the last 660 V substation is Coulsdon North (IIRC). The NLL and Euston - Watford DC electrification remains at 650 V owing to the inteface with the Bakerloo Line at Queen's Park. Beyond there, instead of the standard LU +400 and -230 V arrangement, the outside conductor rail is at 650 V and the centre one is bonded to the running rails; these cross-bonds can be seen at regular intervals. Beyond Harrow and Wealdstone, the redundant centre rail is retained to reduce the resistance of the traction return circuit, as the DC lines only use single-rail track circuits, unlike the Southern which uses double rail. I understand that LUL has a long-term strategy to upgrade the line voltage to 750 V, and all new stock is capable of this, but until the last of the older stock is withdrawn (I believe that the D stock cannot operate at 750 V but subsequent builds can), this will not be possible across the complete network. HTH. |
Upgrading sub surface tube lines to 750V
On Mon, 12 Apr 2010 08:20:25 -0700 (PDT), MIG
wrote: On 12 Apr, 15:28, wrote: On Mon, 12 Apr 2010 14:57:36 +0100 "Peter Corser" wrote: The Central Line is already 750V - it was converted with the last upgrade. Does that mean the western central line can't be used for stock moves any more except for 92 stock? B2003 Doesn't Bakerloo tube stock run on 750 V beyond Queens Park? According to :- http://www.statemaster.com/encyclope...-Great-Britain the DC line is 650v which ISTR has been stencilled on many trackside cabinets for years. OTOH the native trains have been able to run on 750v since at least the c.501 if not also the immediately preceding LMS trains. ATM there doesn't seem to be an "official" confirmation which leaps to the front of the Google queue. |
Upgrading sub surface tube lines to 750V
"Charles Ellson" wrote in message
... the DC line is 650v which ISTR has been stencilled on many trackside cabinets for years. OTOH the native trains have been able to run on 750v since at least the c.501 if not also the immediately preceding LMS trains. ATM there doesn't seem to be an "official" confirmation which leaps to the front of the Google queue. I noticed as I was travelling on the GW main line between Didcot and Paddington that there are lineside cabinets labelled "650V" miles away from the sections where the London Transport lines run alongside - or even where the line is OHLE electrified. From memory I think I saw them around the Maidenhead-Twyford area. What are they for? |
Upgrading sub surface tube lines to 750V
On 13/04/2010 08:06, Mortimer wrote:
"Charles Ellson" wrote in message ... the DC line is 650v which ISTR has been stencilled on many trackside cabinets for years. OTOH the native trains have been able to run on 750v since at least the c.501 if not also the immediately preceding LMS trains. ATM there doesn't seem to be an "official" confirmation which leaps to the front of the Google queue. I noticed as I was travelling on the GW main line between Didcot and Paddington that there are lineside cabinets labelled "650V" miles away from the sections where the London Transport lines run alongside - or even where the line is OHLE electrified. From memory I think I saw them around the Maidenhead-Twyford area. What are they for? they will either be for signalling equipment or for the GSM R transmitters or they could be for the proposed GW line electrification. |
Upgrading sub surface tube lines to 750V
"Hugo Rogers" wrote in message
... On 13/04/2010 08:06, Mortimer wrote: "Charles Ellson" wrote in message ... the DC line is 650v which ISTR has been stencilled on many trackside cabinets for years. OTOH the native trains have been able to run on 750v since at least the c.501 if not also the immediately preceding LMS trains. ATM there doesn't seem to be an "official" confirmation which leaps to the front of the Google queue. I noticed as I was travelling on the GW main line between Didcot and Paddington that there are lineside cabinets labelled "650V" miles away from the sections where the London Transport lines run alongside - or even where the line is OHLE electrified. From memory I think I saw them around the Maidenhead-Twyford area. What are they for? they will either be for signalling equipment or for the GSM R transmitters or they could be for the proposed GW line electrification. Would signalling or GSM use such high voltages? I'd expect low voltages for anything that didn't require large amounts of power and would therefore incur I-squared-R losses. I thought that the proposed GW electrification would be OHLE, so why would it need 650V supplies? |
Upgrading sub surface tube lines to 750V
"Mortimer" wrote Would signalling or GSM use such high voltages? I'd expect low voltages for anything that didn't require large amounts of power and would therefore incur I-squared-R losses. I thought that the proposed GW electrification would be OHLE, so why would it need 650V supplies? What voltage do point motors run at? Peter |
Upgrading sub surface tube lines to 750V
"Mortimer" wrote in message ... "Hugo Rogers" wrote in message ... On 13/04/2010 08:06, Mortimer wrote: "Charles Ellson" wrote in message ... the DC line is 650v which ISTR has been stencilled on many trackside cabinets for years. OTOH the native trains have been able to run on 750v since at least the c.501 if not also the immediately preceding LMS trains. ATM there doesn't seem to be an "official" confirmation which leaps to the front of the Google queue. I noticed as I was travelling on the GW main line between Didcot and Paddington that there are lineside cabinets labelled "650V" miles away from the sections where the London Transport lines run alongside - or even where the line is OHLE electrified. From memory I think I saw them around the Maidenhead-Twyford area. What are they for? they will either be for signalling equipment or for the GSM R transmitters or they could be for the proposed GW line electrification. Would signalling or GSM use such high voltages? I'd expect low voltages for anything that didn't require large amounts of power and would therefore incur I-squared-R losses. I thought that the proposed GW electrification would be OHLE, so why would it need 650V supplies? 650 V is the standard lineside power supply for signalling and comms, so nothing new at all really. Already needed for all the 'non-traction' loads. Paul S |
Upgrading sub surface tube lines to 750V
On Tue, 13 Apr 2010 09:08:00 +0100
"Peter Masson" wrote: "Mortimer" wrote Would signalling or GSM use such high voltages? I'd expect low voltages for anything that didn't require large amounts of power and would therefore incur I-squared-R losses. I thought that the proposed GW electrification would be OHLE, so why would it need 650V supplies? What voltage do point motors run at? I can't imagine them running at 650V would be very healthy for the track maintenance staff! B2003 |
Upgrading sub surface tube lines to 750V
On Tue, 13 Apr 2010 08:59:03 +0100 someone who may be "Mortimer"
wrote this:- Would signalling or GSM use such high voltages? I'd expect low voltages for anything that didn't require large amounts of power and would therefore incur I-squared-R losses. I thought that the proposed GW electrification would be OHLE, so why would it need 650V supplies? 650V, which is low voltage, is the standard signalling supply and has been used since at least the 1960s as part of power signalling schemes. It is used for the same reason that higher voltages are used in electricity distribution systems, to minimise losses and conductor cost. The voltage is reduced and rectified as necessary for use with signalling equipment. -- David Hansen, Edinburgh I will *always* explain revoked encryption keys, unless RIP prevents me http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54 |
Upgrading sub surface tube lines to 750V
On 13 Apr, 10:21, David Hansen
wrote: On Tue, 13 Apr 2010 08:59:03 +0100 someone who may be "Mortimer" wrote this:- Would signalling or GSM use such high voltages? I'd expect low voltages for anything that didn't require large amounts of power and would therefore incur I-squared-R losses. I thought that the proposed GW electrification would be OHLE, so why would it need 650V supplies? 650V, which is low voltage, is the standard signalling supply and has been used since at least the 1960s as part of power signalling schemes. It is used for the same reason that higher voltages are used in electricity distribution systems, to minimise losses and conductor cost. The voltage is reduced and rectified as necessary for use with signalling equipment. Why choose an odd Voltage like 650V? What frequency? Single or three phase? |
Upgrading sub surface tube lines to 750V
On Apr 13, 12:20*pm, Stephen Furley wrote:
Why choose an odd Voltage like 650V? *What frequency? *Single or three phase? Like a lot of things on the railway, its origins are historical. 650 V was the highest value of "medium" voltage under the old Factories Act, which meant that (at that time) a permit-to-work system was not required for "live" work. Such a system of work would these days be illegal under the Electricity at Work Regs, of course. It is single-phase at 50 Hz and it, by the definitons of BS 7671, an "IT" (earth-free) system. This allows the system to continue to operate in the event of a first earth fault, until such time as it can be fixed. Modern signalling power installations have some form of insulation monitoring equipment to measure the resistance between the two conductors (as it's earth-free, we can't really call them "live" and "neutral", of course!) and if it drops below a certain level, an alarm is sent. On electrified lines, this is usually to the electrical control room; on non-electrified lines, to the signal box. The WCML modernisation scheme uses (mostly!) 400 V three-phase, but this has not been a great success owing to the higher currents (and therefore greater number of sources of supply, known as Principal Supply Points or PSPs) required. The 650 V distribution system supplies power to locations known as "Functional Supply Points" from which a spur feeder is taken to a 650/110 V transformer and thence at 110 V into the signalling location cases (the grey boxes you see everywhere and generally referred to as "locs"). On the Western, the FSPs are usually separate from the signalling locs and are identified as such with a yellow stripe. Elsewhere, the 650 V equipment is within the signalling loc case. The policy for main lines now is that the distribution systems have either a PSP at each end (WCML practice) or a PSP at one end and an auxiliary PSP (APSP) at the other (Western practice), to enable resupply in the event of a failure. In particular, a dual-fed system will allow a faulted cable section to be isolated and the two sections to be fed from each end. PSPs have two sources of supply. On DC electrified lines the principal source of supply is from the 33 or 11 kV system that supplies the traction substations, via a step-down transformer to 400 V (which also supplies the local substation loads); usually the signalling supply is taken from one phase (usually red) and stepped up to 650 V. The standby supply is from the mains. On AC electrified lines, the principal source of supply is the mains, with back-up from the 25 kV OLE via a step-down transformer and voltage regulator. This latter is, in effect, a 1:1 auto-transformer with automatic on-load tapchanger, to maintain the output voltage at 650 V. More modern installations use an Uninterruptible Power Supply, which uses a DC link inverter to produce a steady 650 V. These can be seen, for example, on the electrified section of the MML at, for example, Kentish Town, Silkstream Junction, Radlett, St Albans, Luton, Legrave and Bedford. (They look like a small container from the outside.) On non-electrified lines, tjhe principal source of supply is from the mains, with the secondary from a diesel generator. A UPS is used on SSI routes to ensure there is no break in the supply. (Like most electronic equioment, SSI cannot tolerate any significant interruption in supply, whereas a relay interlocking can tolerate the short blip betwen the mains going down and the genny starting up.) At some sites, the genny is three-phase, and at others single-phase, but (except in Scotland), all distribution takes place at 650 V. The Scots have a slightly different system whereby distribution takes place at 400 V and is stepped up to 650 V on each individual feeder. The main reason for this is that given that much of Scotland is sparsely populated, it is easier to hire a 400 V generator in an emergency to connect to the distribution board at a remote site than to keep a stockpile of 650 V gennies, which is the practice elsewhere (especially on the Western). APSPs don't have a standby genny but do have provision for a mobile genny to be brought in. Traditionally, PSPs were located in brick buildings and usually adjacent to a relay room, or in the ground floor of a PSB (eg Exeter, Peterborough, Trent). This is particularly noticeable on the Western, where they often look like a small chalet. On the Eastern and former LMR, they tended to be next to the relay room but in a separate building, with the transformers in a compound in between. (Eg Welwyn Garden City, Hitchin, Royston, Grantham, Newark Northgate, Todmorden (Hall Royd Junction), St Helens Junction.) On the WCML and the early GE and Glasgow schemes, they were an integral part of the feeder station or Track Sectioning Cabin, and not necessarily by a relay room. On the Southern and other DC lines, they are also co-located within the substation. Modern installations tend to be containerised and there is now a move to replacing existing PSPs with containers as the equipment becomes life-expired. Examples of these can be seen at Charfield, Ashchurch and Weston-super-Mare; completely new examples can be found at Wrexham General and Trowell Junction, among others. HTH. |
Upgrading sub surface tube lines to 750V
On Apr 13, 10:48*am, The Gardener wrote:
On Apr 13, 12:20*pm, Stephen Furley wrote: Why choose an odd Voltage like 650V? *What frequency? *Single or three phase? Like a lot of things on the railway, its origins are historical. 650 V was the highest value of "medium" voltage under the old Factories Act, which meant that (at that time) a permit-to-work system was not required for "live" work. Such a system of work would these days be illegal under the Electricity at Work Regs, of course. It is single-phase at 50 Hz and it, by the definitons of BS 7671, an "IT" (earth-free) system. This allows the system to continue to operate in the event of a first earth fault, until such time as it can be fixed. Modern signalling power installations have some form of insulation monitoring equipment to measure the resistance between the two conductors (as it's earth-free, we can't really call them "live" and "neutral", of course!) and if it drops below a certain level, an alarm is sent. On electrified lines, this is usually to the electrical control room; on non-electrified lines, to the signal box. The WCML modernisation scheme uses (mostly!) 400 V three-phase, but this has not been a great success owing to the higher currents (and therefore greater number of sources of supply, known as Principal Supply Points or PSPs) required. The 650 V distribution system supplies power to locations known as "Functional Supply Points" from which a spur feeder is taken to a 650/110 V transformer and thence at 110 V into the signalling location cases (the grey boxes you see everywhere and generally referred to as "locs"). On the Western, the FSPs are usually separate from the signalling locs and are identified as such with a yellow stripe. Elsewhere, the 650 V equipment is within the signalling loc case. The policy for main lines now is that the distribution systems have either a PSP at each end (WCML practice) or a PSP at one end and an auxiliary PSP (APSP) at the other (Western practice), to enable resupply in the event of a failure. In particular, a dual-fed system will allow a faulted cable section to be isolated and the two sections to be fed from each end. PSPs have two sources of supply. On DC electrified lines the principal source of supply is from the 33 or 11 kV system that supplies the traction substations, via a step-down transformer to 400 V (which also supplies the local substation loads); usually the signalling supply is taken from one phase (usually red) and stepped up to 650 V. The standby supply is from the mains. On AC electrified lines, the principal source of supply is the mains, with back-up from the 25 kV OLE via a step-down transformer and voltage regulator. This latter is, in effect, a 1:1 auto-transformer with automatic on-load tapchanger, to maintain the output voltage at 650 V. More modern installations use an Uninterruptible Power Supply, which uses a DC link inverter to produce a steady 650 V. These can be seen, for example, on the electrified section of the MML at, for example, Kentish Town, Silkstream Junction, Radlett, St Albans, Luton, Legrave and Bedford. (They look like a small container from the outside.) On non-electrified lines, tjhe principal source of supply is from the mains, with the secondary from a diesel generator. A UPS is used on SSI routes to ensure there is no break in the supply. (Like most electronic equioment, SSI cannot tolerate any significant interruption in supply, whereas a relay interlocking can tolerate the short blip betwen the mains going down and the genny starting up.) At some sites, the genny is three-phase, and at others single-phase, but (except in Scotland), all distribution takes place at 650 V. The Scots have a slightly different system whereby distribution takes place at 400 V and is stepped up to 650 V on each individual feeder. The main reason for this is that given that much of Scotland is sparsely populated, it is easier to hire a 400 V generator in an emergency to connect to the distribution board at a remote site than to keep a stockpile of 650 V gennies, which is the practice elsewhere (especially on the Western). APSPs don't have a standby genny but do have provision for a mobile genny to be brought in. Traditionally, PSPs were located in brick buildings and usually adjacent to a relay room, or in the ground floor of a PSB (eg Exeter, Peterborough, Trent). This is particularly noticeable on the Western, where they often look like a small chalet. On the Eastern and former LMR, they tended to be next to the relay room but in a separate building, with the transformers in a compound in between. (Eg Welwyn Garden City, Hitchin, Royston, Grantham, Newark Northgate, Todmorden (Hall Royd Junction), St Helens Junction.) On the WCML and the early GE and Glasgow schemes, they were an integral part of the feeder station or Track Sectioning Cabin, and not necessarily by a relay room. On the Southern and other DC lines, they are also co-located within the substation. Modern installations tend to be containerised and there is now a move to replacing existing PSPs with containers as the equipment becomes life-expired. Examples of these can be seen at Charfield, Ashchurch and Weston-super-Mare; completely new examples can be found at Wrexham General and Trowell Junction, among others. Thank you for your comprehensive explanation. Appreciated. |
Upgrading sub surface tube lines to 750V
The WCML modernisation scheme uses (mostly!) 400 V three-phase, but
this has not been a great success owing to the higher currents (and therefore greater number of sources of supply, known as Principal Supply Points or PSPs) required. Ummm.. Rather interesting this but this 400 volt 3 phase supply was "difficult" in quite what way for signalling purposes?.. -- Tony Sayer |
Upgrading sub surface tube lines to 750V
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Upgrading sub surface tube lines to 750V
On Tue, 13 Apr 2010 22:00:22 +0100, tony sayer
wrote: The WCML modernisation scheme uses (mostly!) 400 V three-phase, but this has not been a great success owing to the higher currents (and therefore greater number of sources of supply, known as Principal Supply Points or PSPs) required. Ummm.. Rather interesting this but this 400 volt 3 phase supply was "difficult" in quite what way for signalling purposes?.. As implied above, it requires more transformation points and/or more copper in the ground. If it replaces a single-phase supply, it also (assuming 3P+N) doubles the number of wires to be played with (or stolen) and enables the various "interesting" effects caused by breaks in the neutral or one phase wire without other conductors being interrupted. |
Upgrading sub surface tube lines to 750V
In article , Charles Ellson
scribeth thus On Tue, 13 Apr 2010 22:00:22 +0100, tony sayer wrote: The WCML modernisation scheme uses (mostly!) 400 V three-phase, but this has not been a great success owing to the higher currents (and therefore greater number of sources of supply, known as Principal Supply Points or PSPs) required. Ummm.. Rather interesting this but this 400 volt 3 phase supply was "difficult" in quite what way for signalling purposes?.. As implied above, it requires more transformation points and/or more copper in the ground. If it replaces a single-phase supply, it also (assuming 3P+N) doubles the number of wires to be played with (or stolen) and enables the various "interesting" effects caused by breaks in the neutral or one phase wire without other conductors being interrupted. OK what sort of current draw does a typical signal post, gantry frame, need then?... Suppose in that you could include points motors etc... And that much difference in overall power supplied 650 V single phase rather then I presume 415 or 440 or was it actually 400 three phase?. Take your point re more cable required seem the price of copper is on the up again. Bit on the news of some scrota almost frying himself in a sub station... -- Tony Sayer |
Upgrading sub surface tube lines to 750V
On Wed, 14 Apr 2010 10:28:42 +0100, tony sayer
wrote: In article , Charles Ellson scribeth thus On Tue, 13 Apr 2010 22:00:22 +0100, tony sayer wrote: The WCML modernisation scheme uses (mostly!) 400 V three-phase, but this has not been a great success owing to the higher currents (and therefore greater number of sources of supply, known as Principal Supply Points or PSPs) required. Ummm.. Rather interesting this but this 400 volt 3 phase supply was "difficult" in quite what way for signalling purposes?.. As implied above, it requires more transformation points and/or more copper in the ground. If it replaces a single-phase supply, it also (assuming 3P+N) doubles the number of wires to be played with (or stolen) and enables the various "interesting" effects caused by breaks in the neutral or one phase wire without other conductors being interrupted. OK what sort of current draw does a typical signal post, gantry frame, need then?... The relevant figure is probably something more like how much average current is drawn overall by the various equipment in the general area x miles away at the end of the cable, remembering that other than signal lamps and track circuits ... Suppose in that you could include points motors etc... .... a lot of it is transient. And that much difference in overall power supplied 650 V single phase rather then I presume 415 or 440 or was it actually 400 three phase?. It's years since I played with 3-phase calculations (and in 20 years I only ever had one 3-phase device to deal with) but IIRC the (theoretical) "trick" is that with a balanced load your neutral conductor can be almost non-existent (as occasionally occurs on LU when it gets stolen) thus significantly cutting down on the amount of copper compared with a single-phase circuit delivering the same amount of power over two wires. Someone who has covered the subject rather more recently might be able to do a quick back-of-a-Niquitin-patch calculation but assuming ideal conditions my quick calculation is that the CSA reduction of 3-phase (sans neutral) over 1-phase for the same total current delivered is around 50% although I have a nagging doubt that root-2 comes into it somewhere and pushes the reduction down to 25-33%. Take your point re more cable required seem the price of copper is on the up again. Bit on the news of some scrota almost frying himself in a sub station... |
Upgrading sub surface tube lines to 750V
As implied above, it requires more transformation points and/or more
copper in the ground. If it replaces a single-phase supply, it also (assuming 3P+N) doubles the number of wires to be played with (or stolen) and enables the various "interesting" effects caused by breaks in the neutral or one phase wire without other conductors being interrupted. OK what sort of current draw does a typical signal post, gantry frame, need then?... The relevant figure is probably something more like how much average current is drawn overall by the various equipment in the general area x miles away at the end of the cable, remembering that other than signal lamps and track circuits ... Yes.. Just wondered if that had now fallen due to LED lighting etc?.. -- Tony Sayer |
Upgrading sub surface tube lines to 750V
In uk.transport.london message , Wed, 14
Apr 2010 10:28:42, tony sayer posted: And that much difference in overall power supplied 650 V single phase rather then I presume 415 or 440 or was it actually 400 three phase?. Take your point re more cable required seem the price of copper is on the up again. For the same power, three-phase requires little over half of the amount of conductor in comparison with single-phase. Consider three single- phase supplies driven at 120 degrees to each other : obviously the live wires deliver the same AC current as the live wires in a three-phase supply, but three neutral wires are required. Now join the three neutrals into one; the three return currents, being of different phases, add to nothing, with balanced loads; therefore the neutral, carrying only off-balance currents, can be comparatively thin. See sig. -- (c) John Stockton, near London. Web URL:http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, & links. Correct = 4-line sig. separator as above, a line precisely "-- " (RFC5536/7) Do not Mail News to me. Before a reply, quote with "" or " " (RFC5536/7) |
Upgrading sub surface tube lines to 750V
On Tue, 13 Apr 2010 10:48:59 -0700 (PDT) someone who may be The
Gardener wrote this:- Like a lot of things on the railway, its origins are historical. 650 V was the highest value of "medium" voltage under the old Factories Act, which meant that (at that time) a permit-to-work system was not required for "live" work. Such a system of work would these days be illegal under the Electricity at Work Regs, of course. That is rather amusing on a railway line equipped with unprotected conductor rails energised at a nominal 750 V d.c. (For those who don't know unprotected conductor rails are one of the very few exemptions under the Electricity At Work Regulations 1989). The policy for main lines now is that the distribution systems have either a PSP at each end (WCML practice) or a PSP at one end and an auxiliary PSP (APSP) at the other (Western practice), to enable resupply in the event of a failure. In particular, a dual-fed system will allow a faulted cable section to be isolated and the two sections to be fed from each end. Do you know if switching is automatic, remote,or manual? Perhaps the answer is, it depends:-) Thanks for taking the time to produce a comprehensive posting. I found it very interesting. -- David Hansen, Edinburgh I will *always* explain revoked encryption keys, unless RIP prevents me http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54 |
Upgrading sub surface tube lines to 750V
On Apr 13, 6:48*pm, The Gardener wrote:
650 V was the highest value of "medium" voltage under the old Factories Act, aha ... cue sound of things falling into place ... I did not know that ... a useful fact when trying to understand these things. -- Nick |
Upgrading sub surface tube lines to 750V
On Apr 15, 8:28*pm, David Hansen
wrote: On Tue, 13 Apr 2010 10:48:59 -0700 (PDT) someone who may be The Gardener wrote this:- Like a lot of things on the railway, its origins are historical. 650 V was the highest value of "medium" voltage under the old Factories Act, which meant that (at that time) a permit-to-work system was not required for "live" work. Such a system of work would these days be illegal under the Electricity at Work Regs, of course. That is rather amusing on a railway line equipped with unprotected conductor rails energised at a nominal 750 V d.c. (For those who don't know unprotected conductor rails are one of the very few exemptions under the Electricity At Work Regulations 1989). The policy for main lines now is that the distribution systems have either a PSP at each end (WCML practice) or a PSP at one end and an auxiliary PSP (APSP) at the other (Western practice), to enable resupply in the event of a failure. In particular, a dual-fed system will allow a faulted cable section to be isolated and the two sections to be fed from each end. Do you know if switching is automatic, remote,or manual? Perhaps the answer is, it depends:-) Thanks for taking the time to produce a comprehensive posting. I found it very interesting. -- * David Hansen, Edinburgh *I will *always* explain revoked encryption keys, unless RIP prevents me *http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54 In response to your query about switching, the WCML system has automatic switching, whereas the (significantly cheaper) Western system has manual switching. At the moment, these are the only routes where reconfigurable supplies have been provided. In the case of the Western, this is slowly being rolled out across the system's main lines and is in use of the lines south from Gloucester towards Swindon (the first significant application and primarily as a testbed) and Bristol, for example. Present policy is that if the average cost of delay minutes on a route exceeds a certain amount, then at resignalling, a reconfigurable system is to be provided. This is a fairly recent change of policy, which is why it has only been applied extensively on the WCML. The Western schemes are not, generally, associated with resignallings (except for the new scheme in the Newport area) but are the result of a policy to improve the availability and reliability of sigpower schemes. In response to some other queries raised: The 650 V system supplies all signalling and telecoms loads, interlockings and point machines. In addition, a certain level of emergency lighting at relay rooms is also supplied off the 650 V system. The power supply arrangements at level crossings varies; at some sites all the equipment is supplied from the 650 V system and at others, only the signalling interlockings, with the barriers and lights supplied directly from the mains. Owing to the risk of wrong- side failures caused by a loss of supply, level crossings apart from AOCL and ABCL are fitted with battery back-up and the equipment is supplied directly from the battery, in the manner of a UPS. Telecoms loads are also usually fitted with battery back-up. One of the problems with a three-phase system is that all UK approved signalling equipment is single-phase, and given that point machines tend to have much higher loads than any other equipment (typically 2-3 kVA, whereas most other equipment has demands in the tens of VA), load balancing is difficult. In the case of level crossings, three-phase battery chargers are used. As to why we don't use three-phase point machines, the answer is I don't know, apart from that there are no product-approved examples. They are used elsewhere, so they do exist. I have, somewhere in my possession, a table of typical signalling equipment loads, which I will try to find and summarise on this group next week. As far as LED signals are concerned, I believe that they have a higher demand than bulb signals, owing to the large number of individual LEDs as opposed to a single bulb. Hope this is of further use. |
Upgrading sub surface tube lines to 750V
"Dr J R Stockton" wrote in message nvalid... Now join the three neutrals into one; the three return currents, being of different phases, add to nothing, with balanced loads; therefore the neutral, carrying only off-balance currents, can be comparatively thin. See sig. Or not... Subject to the type of load it is recommended that you up-rate the neutral's Capacitive loads, those with a poor crest factor and high THD will (unchecked) burn your neutral bars/links out in no time at all. This has been a big problem in I.T installs of ye olden days using current kit and high density computing. Then we get into the problems with kVAr... |
Upgrading sub surface tube lines to 750V
On Fri, 16 Apr 2010 01:34:32 +0100, "Q" ..@.. wrote:
"Dr J R Stockton" wrote in message . invalid... Now join the three neutrals into one; the three return currents, being of different phases, add to nothing, with balanced loads; therefore the neutral, carrying only off-balance currents, can be comparatively thin. See sig. Or not... Subject to the type of load it is recommended that you up-rate the neutral's Doesn't the cheat for that one involve the use of star-delta transformers at each end of the circuit (i.e. no neutral at all on the "trunk" part of the circuit) and controlling the out-of-balance currents appropriately ? Capacitive loads, those with a poor crest factor and high THD will (unchecked) burn your neutral bars/links out in no time at all. This has been a big problem in I.T installs of ye olden days using current kit and high density computing. Then we get into the problems with kVAr... |
Upgrading sub surface tube lines to 750V
I have, somewhere in my possession, a table of typical signalling
equipment loads, which I will try to find and summarise on this group next week. As far as LED signals are concerned, I believe that they have a higher demand than bulb signals, owing to the large number of individual LEDs as opposed to a single bulb. Hope this is of further use. Very interesting that .. be nice to see the table you refer to in due course.. -- Tony Sayer |
Upgrading sub surface tube lines to 750V
In uk.transport.london message
, Fri, 16 Apr 2010 01:34:32, Q posted: "Dr J R Stockton" wrote in message . invalid... Now join the three neutrals into one; the three return currents, being of different phases, add to nothing, with balanced loads; therefore the neutral, carrying only off-balance currents, can be comparatively thin. See sig. Or not... Subject to the type of load it is recommended that you up-rate the neutral's Capacitive loads, those with a poor crest factor and high THD will (unchecked) burn your neutral bars/links out in no time at all. Symmetrical linear loads, such as pure capacitative or inductive, maintain the balance of neutral currents, by symmetry. Third (and its multiples) harmonic distortion currents will add in the neutral rather than cancelling. But it takes a lot of THD to give the same current in the neutral as is in each of the lives. In the quoted part, "comparatively" is a comparison between the joined neutral and the three unjoined ones; and "thin" really means cross- section rather than diameter. -- (c) John Stockton, near London. Web URL:http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, & links. Correct = 4-line sig. separator as above, a line precisely "-- " (RFC5536/7) Do not Mail News to me. Before a reply, quote with "" or " " (RFC5536/7) |
Upgrading sub surface tube lines to 750V
On Apr 12, 2:57*pm, "Peter Corser"
wrote: The Central Line is already 750V - it was converted with the last upgrade.. Was it ? Not according to what I see , and what I have checked on, today, with the DC traction SCADA indicating line wide values fluctuating around 620 +/- 10 V ... that suggests its 630 V -- Nick |
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