ECML Power Supply Upgrade

[Mcq]

Many thanks again - my remaining question is where does any regenerative breaking power go if there are no other trains within the section - resistors?

 

[zwk500]

The reason for neutral sections is fundamentally because different parts of the OLE are fed from different phases of the Grid, so they are out of phase with each other and a major short circuit would result if they were electrically connected. In theory, SFCs could make the entire OLE network synchronised so that neutral sections were unnecessary. However I think that would cause other complications, such as what happens if there is a short circuit being fed from more than one place rather than just one at present.

Unless the above is achieved, I don't think the SFCs reduce the number of neutral sections, and they may even increase if there are more small feeders feeding to smaller areas of OLE.

You'd also want to keep neutral sections for isolation purposes.

 

[59CosG95]

You'd also want to keep neutral sections for isolation purposes.

Indeed, although Insulated Overlaps also serve the same purpose.

 

[zwk500]

Indeed, although Insulated Overlaps also serve the same purpose.

Ooh, don't know about them, is it as simple as just isolating the end of one wire and start of the next while they run parallel through the changeover section? Presumably they still need to have a brief moment of no power to the train?

 

[swt_passenger]

Many thanks again - my remaining question is where does any regenerative breaking power go if there are no other trains within the section - resistors?

Normally on 25kV systems regenerated power will go back into the grid. I expect, (but don’t know), that the SFCs will be able to operate in reverse.

 

[59CosG95]

Ooh, don't know about them, is it as simple as just isolating the end of one wire and start of the next while they run parallel through the changeover section? Presumably they still need to have a brief moment of no power to the train?

Not quite as simple as that, sadly! At overlaps, one of the two wire runs above a given track is 'out-of-running' (i.e. not in contact with the pantograph) at support A, with the other being in-running; these switch positions at support B.
Near each of these supports, the OOR wire can have insulation placed in both the catenary & contact wire, with either an isolator or booster transformer connected around the section break. In regular service, the isolator bypasses the insulation, keeping current flowing, but can open its switchgear to isolate the electrical section between there and the next sectioning site (which may be another insulated overlap or a neutral section).

 

[Mcq]

Normally on 25kV systems regenerated power will go back into the grid. I expect, (but don’t know), that the SFCs will be able to operate in reverse.

I wonder if SFCs can operate in reverse - very complicated electronics if they do?

 

[zwk500]

Not quite as simple as that, sadly! At overlaps, one of the two wire runs above a given track is 'out-of-running' (i.e. not in contact with the pantograph) at support A, with the other being in-running; these switch positions at support B.
Near each of these supports, the OOR wire can have insulation placed in both the catenary & contact wire, with either an isolator or booster transformer connected around the section break. In regular service, the isolator bypasses the insulation, keeping current flowing, but can open its switchgear to isolate the electrical section between there and the next sectioning site (which may be another insulated overlap or a neutral section).

So an Isolated Overlap would avoid the momentary loss of power?

 

[swt_passenger]

I winde if SFCs can operate in reverse - very complicated electronics if they do?

The device we usually call a traction converter in a train is effectively a reversible SFC, it’s just got to be scaled up to handle higher currents. I don’t think the electronics to do that at a substation would be significantly more complicated, just bigger.

 

[Mcq]

The device we usually call a traction converter in a train is effectively a reversible SFC, it’s just got to be scaled up to handle higher currents. I don’t think the electronics to do that at a substation would be significantly more complicated, just bigger.

Thank you

 

[Bald Rick]

Many thanks again - my remaining question is where does any regenerative breaking power go if there are no other trains within the section - resistors?

I wonder if SFCs can operate in reverse - very complicated electronics if they do?

Yes they do, and it goes back to the grid.

 

[edwin_m]

A 25kV feeder generally a wide area, and because of the low current a train can use regenerated energy from another one some distance away without it all being lost in the impedances (both unlike the third rail system). So I wonder how often an SFC would actually return regenerated power to the grid in reality.

25kV trains always have some means of dumping the braking energy on board if the line isn't receptive - they have to have this anyway otherwise they wouldn't be able to brake in the event of loss of supply. For most trains it's resistors, but I think I read that the Class 93 didn't have room for them so will revert to friction braking if its on-board battery is fully charged.

 

[Mcq]

Yes they do, and it goes back to the grid.

Excellent - thanks Bald Rick for definitive answer as usual.

Presumably the SFC output frequency is a stable 50Hz independant of any deviations on the grid - useful when on those rare occasions the grid goes beyond the tolerance of, say class 700s
Also presumably, the output phase can be locked to adjacent sections allowing longer sections and/or feeding from both ends?

 

[Watershed]

For most trains it's resistors, but I think I read that the Class 93 didn't have room for them so will revert to friction braking if its on-board battery is fully charged.

Regenerative braking is mostly just a supplemental brake used to reduce wear on the brake system. The brakes are always going to be capable of delivering the required braking rate on their own (e.g. if the regen braking is isolated due to a fault).

 

[Snow1964]

Regenerative braking is mostly just a supplemental brake used to reduce wear on the brake system. The brakes are always going to be capable of delivering the required braking rate on their own (e.g. if the regen braking is isolated due to a fault).

Regenerative braking is only used above certain speeds, below a set speed the friction brakes are blended in.

Regenrestive braking doesn’t really work at speeds below about 10-15mph (depends on gearing), the slow motor doesn’t generate enough electrical energy to dissipate the speed, and provide smooth braking, so friction brakes do the final slowing to a stop

 

[Mcq]

Thanks all for great replies.
Indeed I think I first became aware of regenerative breaking with highway coaches fitted with Tesla braking.
What I have wondered is just how much power actually gets recycled - other than in heat - that's not to deminish its importance in reducing brake ware.

 

[swt_passenger]

Thanks all for great replies.
Indeed I think I first became aware of regenerative breaking with highway coaches fitted with Tesla braking.
What I have wondered is just how much power actually gets recycled - other than in heat - that's not to deminish its importance in reducing brake ware.

Network Rail have some standard figures for use when trains aren’t individually metered, It’s around about 15% averaged out, but the actual figure depends on the type of stopping pattern.

Post #28 in a recent thread has some details:

How are train companies charged for electricity?

It has taken a long time for these questions to occur to me. Can train companies bargain with electricity suppliers, and Network Rail acts as network provider, or does NR buy all the power and sell it on? If the latter, does NR have to charge a flat rate based on usage, or can large users get a...

www.railforums.co.uk

 

[Mcq]

Network Rail have some standard figures for use when trains aren’t individually metered, It’s around about 15% averaged out, but the actual figure depends on the type of stopping pattern.

Post #28 in a recent thread has some details:

How are train companies charged for electricity?

It has taken a long time for these questions to occur to me. Can train companies bargain with electricity suppliers, and Network Rail acts as network provider, or does NR buy all the power and sell it on? If the latter, does NR have to charge a flat rate based on usage, or can large users get a...

www.railforums.co.uk

Thank you very much

 

[Bald Rick]

Presumably the SFC output frequency is a stable 50Hz independant of any deviations on the grid - useful when on those rare occasions the grid goes beyond the tolerance of, say class 700s

I’m no expert on this, but yes I think that’s right.

Also presumably, the output phase can be locked to adjacent sections allowing longer sections and/or feeding from both ends?

Probably possible in theory, but I doubt very much if that would happen.

What I have wondered is just how much power actually gets recycled

Well, that depends. AIUI the efficiency of an AC electric motor when acting as an alternator is about 80%, ie if you used 10kWh of energy to get a train up to (say) 60mph, then you would get back 8kWh braking it from 60mph to a stand, assuming the regen was used for all the braking (sometimes it is, sometimes it isn’t) and not allowing for the effects of air resistance etc.

But, of course, most trains are not just accelerating then immediately braking. Almost all services have a spell at constant speed, and the energy they use doing this is simply overcoming air and rolling resistance. This can not be recovered.

On top of all this, there is the electricity the train takes to power the ‘hotel’ facilities - aircon, heating, lighting, info systems and all the train management systems. None of this is recoverable.

All told, typical energy recovery varies from about 10% to 40%, depending on the duty cycle of the service (ie how often it starts and stops).

 

[Scotrail88]

Do we know when the upgrade will complete on the northern (Scottish) section to allow TPE to run electric?

How will he new open access cope as believe electric only units.

Surely with environmental concerns, this must be priority to sort.

 

[Bald Rick]

Do we know when the upgrade will complete on the northern (Scottish) section to allow TPE to run electric?

2023/4.

But it’s not about TPE (and it’s anyones guess if they will be running north of Newcastle anyway).

 

[edwin_m]

Regenerative braking is only used above certain speeds, below a set speed the friction brakes are blended in.

Regenrestive braking doesn’t really work at speeds below about 10-15mph (depends on gearing), the slow motor doesn’t generate enough electrical energy to dissipate the speed, and provide smooth braking, so friction brakes do the final slowing to a stop

I believe this is better with AC motors, although they may actually be using power from the supply to generate the magnetic field in the motors. Certainly when we were testing the Croydon trams in 1998 the friction brake didn't come in until much lower speeds (2-3km/h I think).

 

[AM9]

... All told, typical energy recovery varies from about 10% to 40%, depending on the duty cycle of the service (ie how often it starts and stops).

That all makes sense. Counterintuitively that can be read as if a train running a frequent stopping service recovers more energy and is therefore more efficient. However, it would have to draw the power to accelerate each time in the first place, so the inefficiency of the acceleration power draw and the deceleration regen cycles still apply. Conversely a non-stop train doesn't recover much energy, but it drawas a lot less overall as it is just maintaining it's speed most of the time.

 

[Nicholas Lewis]

For those interested in the nitty gritty of the ECML power upgrade, there’s a couple of planning applications on Northumberland Council planning site for the 2 new SFCs and replacement Feeder Station at Marshall Meadows. The paperwork for the two applications is very similar, they both have the same main drawings, so I couldn’t work out why they’re separate.

20/03458/FUL Change of use from agricultural land to operational railway to facilitate the siting of 1x Feeder Station and associated works in connection with power supply upgrade of the East Coast Main Line | East Coast Electrical Substation South East Of Marshall Meadows Berwick-Upon-Tweed Northumberland.

20/03459/FUL | Change of use : agricultural to operational railway for siting of 2 x Static Frequency Converters and associated works in connection with power supply upgrade of the East Coast Main Line | East Coast Electrical Substation South East Of Marshall Meadows Berwick-Upon-Tweed Northumberland.

When we discussed Marshall Meadows grid connections a few months ago there was some doubt about the supply voltage, and I quoted the openinfrastructure map which showed 33kV, but the drawings provided here refer to 132kV supplies to the SFC compounds via 6 underground cables fed from the existing grid compound. That suggests an upgrade to 3 phase for the overhead grid supply from High Cocklaw. (Grid = Scottish Power Electricity Network (SPEN) at this location, although in England.)

I’ve attached an image of a pdf drawing, it is a relatively massive site compared to the existing NR Feeder Station that will be removed, that is shown lower right in green between the SPEN compound and the ECML.

Hope this is of interest:

View attachment 97860

Another example of how economical BR 25kV designs were.

I believe this is better with AC motors, although they may actually be using power from the supply to generate the magnetic field in the motors. Certainly when we were testing the Croydon trams in 1998 the friction brake didn't come in until much lower speeds (2-3km/h I think).

Correct AC motors can provide almost full retard force down to a standstill.

 

[Mcq]

Correct AC motors can provide almost full retard force down to a standstill

Certainly I watched a 717 approach our local station and I could see the brakes -- they didn't engage until the train was almost stationary - almost like a hand brake - I was impressed - no wonder the brake shoes will last longer.

 

[Bald Rick]

Certainly I watched a 717 approach our local station and I could see the brakes -- they didn't engage until the train was almost stationary - almost like a hand brake - I was impressed - no wonder the brake shoes will last longer.

Ah - the Class 700s and 717s (and I assume 701s) have tread brakes as well as disc brakes. So the disc brakes might have been deployed, but you wouldn’t have been able to see those.

In autumn or other conditions of poor adhesion, the tread brakes are used much more to help keep the wheels clean.

That all makes sense. Counterintuitively that can be read as if a train running a frequent stopping service recovers more energy and is therefore more efficient. However, it would have to draw the power to accelerate each time in the first place, so the inefficiency of the acceleration power draw and the deceleration regen cycles still apply. Conversely a non-stop train doesn't recover much energy, but it drawas a lot less overall as it is just maintaining it's speed most of the time.

Well I guess that depends on how you view efficiency. I’m fairly sure (= educated guessing) that over a given stretch of track, a unit that is stop / starting will use less electricity than a train starting at one end and running non stop to the other end. It will take longer obviously. This is the same principle that sees electric cars have longer range on stop start runs in heavy traffic than on primarily motorway driving.

 

[swt_passenger]

Another example of how economical BR 25kV designs were.

Well yes, but the entire feeding system in the Northumberland and Borders area was designed to the minimum capacity they could get away with, limited and poor quality supplies generally fed from the local distribution network rather than the high voltage grid, excess distances between feeders, and a planning assumption that many trains would remain diesel.

So what is being installed now is actually fit for present and future traction demands, while presenting a stable load to the distribution network operator (DNO).

 

[Nicholas Lewis]

Well yes, but the entire feeding system in the Northumberland and Borders area was designed to the minimum capacity they could get away with, limited and poor quality supplies generally fed from the local distribution network rather than the high voltage grid, excess distances between feeders, and a planning assumption that many trains would remain diesel.

So what is being installed now is actually fit for present and future traction demands, while presenting a stable load to the distribution network operator (DNO).

Northumberland and the Borders were designed with what the CEGB were able to offer due to the limited 132kV infrastructure in the area thats why its constrained but its supported the service until TPE came along. The reality was in the 1980s BR was managing a railway with the status quo in mind and convincing the treasury to invest in anything was a challenge. However, the ECML system design was optimised for the passenger timetable demand that was required in the mid 1980's but fortuitously it did build in one electric freight path per hour which IC effectively utilised over the following years. People have to remember that BR was very cash constrained and in this era and the budget was £400m (£1.3B in 2021 OK there was a different way of accounting of renewals works and staff costs so probably £2B) for electrification, resignalling and 31 class 91's and MkIV's. This required engineers to be economical with there designs and whilst not perhaps being as resilient as people would expect today I would argue what they delivered has served the industry and the nation well. Furthermore, had these engineers not risen to the challenge many routes would have been lost and we wouldn't be in the great position of being able to upgrade lines now because of the industries success. Also as a result of the industries success, notwithstanding C19, it is able to seek and get approval to future proof what it builds today which BR never had the opportunity to do.

 

[Bald Rick]

Northumberland and the Borders were designed with what the CEGB were able to offer due to the limited 132kV infrastructure in the area thats why its constrained but its supported the service until TPE came along. The reality was in the 1980s BR was managing a railway with the status quo in mind and convincing the treasury to invest in anything was a challenge. However, the ECML system design was optimised for the passenger timetable demand that was required in the mid 1980's but fortuitously it did build in one electric freight path per hour which IC effectively utilised over the following years. People have to remember that BR was very cash constrained and in this era and the budget was £400m (£1.3B in 2021 OK there was a different way of accounting of renewals works and staff costs so probably £2B) for electrification, resignalling and 31 class 91's and MkIV's. This required engineers to be economical with there designs and whilst not perhaps being as resilient as people would expect today I would argue what they delivered has served the industry and the nation well. Furthermore, had these engineers not risen to the challenge many routes would have been lost and we wouldn't be in the great position of being able to upgrade lines now because of the industries success. Also as a result of the industries success, notwithstanding C19, it is able to seek and get approval to future proof what it builds today which BR never had the opportunity to do.

Also worth remembering that Newcastle - Edinburgh was not part of the ECML electrification when it was first presented to the DfT for Authority. That was added on later, as an ‘even cheaper than chips’ extra.

 

[WAO]

Also the Tory ministers at the time were sympathetic to BR. Nicholas Ridley was SoS and a civil engineer, with David Mitchell (father of present Andrew M) as railways minister. I believe that it was Ridley who thought it nonsense to terminate at Newcastle. It helped that BR was a competent outfit that delivered ECEP on time and to budget and with one serious accident when a cable snapped.

The Thatcher paradox

WAO