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Is the leccy supply to the railway 'just enough'?

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AM9

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Actually more embarrassing - the wrong frequency values being put in the software for the limits, the start shedding load value was use as the value to shed all load...
The frequency never went below the shed all load value in the standards so no resets should have been need let alone drivers not being able to do them!
Swiss cheese failure model at work there.
OK, thanks both for the corrections. It was discussed at length but I don't recall all of that coming out. There was a change in the maximum allowable frequency variation duration on the National Grid which presumably wasn't properly allowed for in the software as well.
 
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edwin_m

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Wasn't the Woodhead line a special case benefitting from a fairly uniform train type, i.e. class 76 locos with long slow drags up each side of to Pennines matched by long falls in the opposite direction. This meant that there was an almost continuous demand for the regenerated energy for much of the day. On a metro or commuter line, the sheer density of traffic will likely aggregate to give a fairly continuous regen supply matching the demand. With ac electrification, the situation is much less critical because the regen. AC is available direct from the trains and usually is directly available to a much larger population of trains. An additional gain is the practicality of feeding back power into the grid where there is always a much more constant demand in which to sink the energy.
If the line [or third rail] isn't receptive, the line voltage will go up, and the train then needs to stop regenerating before it goes beyond an upper limit. Modern trains can detect this very quickly and stop regenerating, to the extent that when we tested the Croydon tram we found that if the line was totally unreceptive it would oscillate in and out of regeneration at a rate that was in the audio frequencies. (This would never happen in practice, there was only one tram on the network at the time and even turning the heater on created enough receptivity to stop it happening).

Trains must also avoid regenerating into a dead line, because the reason it's dead might be because someone is working on it. This is one reason why traction power must also be earthed when an "isolation" is needed.

The rate of rise of the line voltage will depend on the capacitance on the line, which from the above I assume is low enough to give a time constant in the milliseconds with the current being regenerated. I imagine the 76s didn't have anything as clever as automatic shutoff of regeneration when the line voltage went up, so the drivers probably had to keep a very close eye on the line volts when regenerating.
 

Ken H

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If the line [or third rail] isn't receptive, the line voltage will go up, and the train then needs to stop regenerating before it goes beyond an upper limit. Modern trains can detect this very quickly and stop regenerating, to the extent that when we tested the Croydon tram we found that if the line was totally unreceptive it would oscillate in and out of regeneration at a rate that was in the audio frequencies. (This would never happen in practice, there was only one tram on the network at the time and even turning the heater on created enough receptivity to stop it happening).

Trains must also avoid regenerating into a dead line, because the reason it's dead might be because someone is working on it. This is one reason why traction power must also be earthed when an "isolation" is needed.

The rate of rise of the line voltage will depend on the capacitance on the line, which from the above I assume is low enough to give a time constant in the milliseconds with the current being regenerated. I imagine the 76s didn't have anything as clever as automatic shutoff of regeneration when the line voltage went up, so the drivers probably had to keep a very close eye on the line volts when regenerating.
The 76's were later fitted with rheostatic braking so electric braking could continue when the line could not accept regeneration power. Probably a new circuit using existing resistors.
 

Nicholas Lewis

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And as the voltage starts to drop the distribution losses (up until the shoes) go up, 3rd rail regen has some useful indirect effects at increasing the average 3rd rail voltage and reducing losses which improves the overall power supply situation more than might be expected looking at it simplistically.
Losses in the third rail are resistive and thus with the high currents involved at 750V losses are directly proportional to the amount of current being drawn. Its voltage that drives current so if voltage drops current drops although in modern EMUs with VVVF inverters they attempt to draw more current to compensate for voltage drop to try and maintain power.
I'm no expert, but I suspect that's exactly what a track paralleling hut does. Connecting the two lines to one another at regular intervals reduces the overall impedance (resistance) of the system and therefore reduces losses and reduces the voltage drop.
Thats correct but in reality TPH's were used was to extend the distance between substations to lower capital costs so didn't have that big an impact on resistive losses across the Southern region. However, NR's more recent power upgrades have predominantly converted TPHs to substations and this helps in lowering restive losses although this may have an adverse impact on how receptive the system is to regeneration as average voltage on the conductor rail will be higher.
 

Class 170101

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The issue at Skipton was that - because the electrification was done, like many other schemes, on a financial shoestring and it was deemed highly unlikely to ever extend beyond Skipton - the final twelve miles of the route were fed by a single feeder station at Bingley, where there would normally be another at Skipton, had it been on a through electrified route. This had a twofold effect on the route: firstly that the voltage dropped to about 17 Kv by Skipton and secondly, because of the lack of a feeder station and associated neutral section at Skipton South, it was - and still is - impossible to keep Skipton station and sidings live when there is a planned or unplanned electrical isolation of the section from Bingley. This causes all sorts of issues with the overnight unit shunting, washing and cleaning at Skipton and involves a lot of careful planning by the night shunt drivers, signallers and electrical controllers. Although I have been retired for nine years, I'm not aware of a new feeder station having been built between Keighley and Skipton. I believe it was more a matter of upgrading the existing feeder at Bingley with additional equipment to boost the supply for running the 91s....and now the Azumas.

I guess it wouldn't be possible to run an extension lead from Bingley Feeder Station to Skipton and feed Skipton station area only if there was a need to isolate the rest of the line?

Regarding the Blackpool North electrification are all the feeder stations built as planned? I heard there might be one thats not been built that was planned for.

Firstly the voltage drops, which does mean there’s less power at the train (so it accelerates a little more slowly), but then the breakers start tripping in the substations.
The less computer operated trains tend to be happier at running at lower voltages than they are meant to be operated at (ie 25KV), comparing Class 360s with Class 321s the latter seemed happier to carry on unlike their newer counterparts in my experience.
 
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Bald Rick

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The less computer operated trains tend to be happier at running at lower voltages than they are meant to be operated at (ie 25KV), comparing Class 360s with Class 321s the latter seemed happier to carry on unlike their newer counterparts in my experience.

Not necessarily. The Hitachi trains are much more accommodating to voltage drops than Class 91s for example.
 

WAO

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It would make more sense to have a battery-electric shunter for outages, if they're that often (an 08 with a battery?). It could be charged off the OLE or more likely a ground supply. Looking at the Grid map, there's not much between Leeds and Carlisle to drive a Feeder Station, (rather a luxury here) unless it were a SFC running off the DNO's 33kV circuit.

WAO
 

Jozhua

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Not necessarily. The Hitachi trains are much more accommodating to voltage drops than Class 91s for example.
Generally digital systems are more resilient than their analogue counterparts. The issue is when you introduce programmers who have absolutely no concept of how their code will be used in the real world. This results in little/no resiliency for external devices failing (e.g. power dropping) and poor user feedback (e.g. non-specific, difficult to understand, error codes). Most of this can be attributed to laziness and silly management practices - See: Agile.

I can absolutely see how different implementations of these systems could result in very different levels of reliability in a trains computer systems. It does not surprise me that Hitachi trains are accommodating in this manner, generally the Japanese do well in building for resiliency.
 

HSTEd

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I would humbly suggest that in the long run it would probably be better to pay for the railway to buy fully controlled rectifier substations than mess around with batteries all over the place.

Battery availability is likely to be a constraint on decarbonisation for the next couple of decades, so conserving batteries where they are not required is probably the better move.
 

GRALISTAIR

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I would humbly suggest that in the long run it would probably be better to pay for the railway to buy fully controlled rectifier substations than mess around with batteries all over the place.

Battery availability is likely to be a constraint on decarbonisation for the next couple of decades, so conserving batteries where they are not required is probably the better move.
And the Hydrogen infrastructure is not in place yet nor will be for a while either. MEGA
 

Elecman

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Regarding the Blackpool North electrification are all the feeder stations built as planned? I heard there might be one thats not been built that was planned for.
there were no feeder stations planned for Preston-Blackpool North, the Sectioning Cabins were installed as planned at Kirkham and Blackpool North
 

Nicholas Lewis

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I would humbly suggest that in the long run it would probably be better to pay for the railway to buy fully controlled rectifier substations than mess around with batteries all over the place.

Battery availability is likely to be a constraint on decarbonisation for the next couple of decades, so conserving batteries where they are not required is probably the better move.
On the DC systems you would still have the resistive loses in the conductor rail but that needs to balanced off with the extra energy karting around the batteries. The capital costs would be pretty large and in old railway would have to paid for through higher track access charges although in the new GBR world they should be remitted by govt to minimise overall energy demand for running the system though.
 

snowball

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there were no feeder stations planned for Preston-Blackpool North, the Sectioning Cabins were installed as planned at Kirkham and Blackpool North
Sorry to be ignorant but why is a sectioning cabin needed at the end of the line? (Unless perhaps to earth the overhead when works are going on???).
 

HSTEd

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Sorry to be ignorant but why is a sectioning cabin needed at the end of the line? (Unless perhaps to earth the overhead when works are going on???).

Given the complexity of the station it may be considered desirable to have granularity in overhead wiring energisation in the station complex.

So they can knock out platforms without taking them all out for example.
 

janahan

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Generally digital systems are more resilient than their analogue counterparts. The issue is when you introduce programmers who have absolutely no concept of how their code will be used in the real world. This results in little/no resiliency for external devices failing (e.g. power dropping) and poor user feedback (e.g. non-specific, difficult to understand, error codes). Most of this can be attributed to laziness and silly management practices - See: Agile.

I can absolutely see how different implementations of these systems could result in very different levels of reliability in a trains computer systems. It does not surprise me that Hitachi trains are accommodating in this manner, generally the Japanese do well in building for resiliency.
As a software developer I do find your comment extremely condescending and quite harmful to an entire industry, especially the "Agile" method, which when done correct, has been proven in more cases than not to actually produce better quality code, that matches specifications far better.

In my experience, issues are almost always created due to poor specifications or communications. We software developers are NOT railway engineers, train drivers, etc. We dont and more importantly are not EXPECTED to know all the nuances of the railway, just like the engineers and drivers are not expected to know programmign and how software is made.

All the details need to be specified in the requirements, otherwise the developer may not know about it. Indeed, even if a developer sees a issue that is not in the specs, we often do approach the client to try and discuss the resolution to it, and in some cases the client works with us, in other cases, the client doesnt care, putting us in a dilema.

Note the Agile method you are pretty much critisizing orinated in Japan and is used by the Japanese extensively, including Hitachi, having worked with them before. In japanese companies, the software developers and engineers (and all other sections) work better at communicating, hence the "better quality". Sadly in many traditional western companies, there is no such good communication, as well as a lot of interference by accounting, MBEs and other persons who are trying to justify their positions and push costs and other agendas over quality.

I have worked for good companies and poor companies, even different projects within the same company where communication/specifications were great versus very poor, and seen the resulting software.
 

najaB

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In my experience, issues are almost always created due to poor specifications or communications.
Also working in IT I've lost track of the number of times that a client has, when the project is delivered, said some variation of "Yes that's what I asked for, but it's not what I wanted!"
 

Ediswan

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In my experience, issues are almost always created due to poor specifications or communications.
Which is itself difficult. Sometimes, day to day use of an existing system will rely on a behaviour that is not part of the formal specification. When the time comes to develop the new version of that system, this behaviour may not get added to the specification, and hence not be replicated. Which eventually leads to "The old system used to let me do X, I relied on that every day to get the job done".
 

najaB

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Which is itself difficult. Sometimes, day to day use of an existing system will rely on a behaviour that is not part of the formal specification. When the time comes to develop the new version of that system, this behaviour may not get added to the specification, and hence not be replicated. Which eventually leads to "The old system used to let me do X, I relied on that every day to get the job done".
Which emphasises why the best projects seek input from the stakeholders (usually the people paying for the project) to get the high-level requirements, then the subject matter experts (the people with specialist knowledge) to validate that those high-level requirements are realistic and the final product is something that they can actually use, and finally the business matter experts (experienced users) to fine tune details of the user experience/interface.

In the context of the railway specifying new rolling stock the stakeholders would be the ROSCOs/DfT/Transport Scotland to get things like the performance numbers that they need to implement their timetables, the subject matter experts would be groups like the fitters and Network Rail to ensure that the rolling stock is compatible with the infrastructure/facilities and can can actually be maintained, and the business matter experts would be drivers to ensure that the buttons, levers and knobs are where they expect them to be and do what they expect them to do.
 

Dai Corner

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Which emphasises why the best projects seek input from the stakeholders (usually the people paying for the project) to get the high-level requirements, then the subject matter experts (the people with specialist knowledge) to validate that those high-level requirements are realistic and the final product is something that they can actually use, and finally the business matter experts (experienced users) to fine tune details of the user experience/interface.

In the context of the railway specifying new rolling stock the stakeholders would be the ROSCOs/DfT/Transport Scotland to get things like the performance numbers that they need to implement their timetables, the subject matter experts would be groups like the fitters and Network Rail to ensure that the rolling stock is compatible with the infrastructure/facilities and can can actually be maintained, and the business matter experts would be drivers to ensure that the buttons, levers and knobs are where they expect them to be and do what they expect them to do.
No place for the passenger, who's going to ride in the finished train (or not, if he doesn't like it) and is also probably a taxpayer who is ultimately funding it?

Sounds like mind reading is now a required skill for good project management.
Questioning, and listening to the answers, is.
 

GRALISTAIR

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Questioning, and listening to the answers, is.
Agreed especially on the LISTENING. Too many people want to show they are important or justify their jobs by talking. More listening carefully with the occasional probing question is absolutely necessary. Reminds me of a Godfather quote from Don Corleone about he loves his children (specifically Sonny) but they talk when they should be listening.
 

najaB

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No place for the passenger, who's going to ride in the finished train (or not, if he doesn't like it) and is also probably a taxpayer who is ultimately funding it?
Passenger...??? I'm sure I heard that word before but no idea what it means.

Realistically, the stakeholders will most likely be the ones specifying the passenger environment and the SMEs will probably chip in, but there's almost no point asking the passengers as you will never be able to satisfy them all. Just look at the never-ending debates on here about seats! Just make sure that it meets the relevant standards and won't actually kill or maim anyone and you're good go.
 
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Ken H

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Also working in IT I've lost track of the number of times that a client has, when the project is delivered, said some variation of "Yes that's what I asked for, but it's not what I wanted!"
'why did you sign off the spec then?'
 
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