Alternative To Third Rail?

hwl said:

No I'm suggesting engineering for the requirements of the route not massively under-engineering which you are assuming to help self justify your thinking.

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Allowing for the existing timetable as the baseline is massively under-engineering?
If they want additional trains, then that would put in in the project scoping phase.
Or allowances would be made for additional substation capacity to be cheaply added later should the demand arise if it is merely aspirational.
The topology I propose would allow a substation to be added cheaply at intermediate points should traffic demand increase, and could be any size you wish up to the maximum rating of the rail itself, depending of what drops out of your output specification.

hwl said:

The entire SWML timetable is still limited by decisions taken planning during the Bournemouth electrification project 54-55 years ago so best not to repeat with similar under engineering in the future?

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So best not have any electrification at all?
Because that is where this argument goes.

As the reports into problems with infrastructure projects like GWRM have stated, overly specified infrastructure is a massive problem for the railway and in British infrastructure projects more generally.

hwl said:

In many locations the only need for DNO network enhancements would be rail electrification so the cheapest way to pay for it is doing it directly especially when you see the DUOS charges as well.

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That would drop out of the detailed project specification phase. But given the low traffic density on routes that I am considering I can't see a 33kV feeder cable being a reasonable solution.

There is a maximum of four CLass 444 units west of Salisbury given the timetable and train length restrictions - that would imply a total maximum load around 8MW... which is getting on for the rating of a single 11kV feeder, let alone a 33kV one.

hwl said:

Given that everyone else with experience doesn't agree with your analysis might suggest some more detailed recalculation is needed?

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Many of the commenters started citing figures to justify their positions which are well away from the traffic densities on the routes I am considering for this topology.
They appear to be commenting based on third rail retaining the traditional Southern Region derived topology which takes no account for developments in controlled rectifier technology.

If they want me to run calculations for a given route, give me said project and I will try to run numbers for it.

In some cases indeed a HV fed substation would be the best solution - the key thing here is by breaking up the quanta of rectification and spreading it along the line, engineered so they can cooperate, we can drive losses down and ameliorate many of the cited problems with third rail as a solution

EDIT:

Also why does a Class 700 have so much installed power? (5000kW at rail?)
It is 12 cars long, but then the 100mph Class 707 which is five cars long and is also a Desiro city only has 1200kW installed power, both according to Siemens.
Even scaling that to ten cars only gives me ~2900kW
Is this just an AC versus DC thing?

HSTEd said:

Allowing for the existing timetable as the baseline is massively under-engineering?
If they want additional trains, then that would put in in the project scoping phase.
Or allowances would be made for additional substation capacity to be cheaply added later should the demand arise if it is merely aspirational.
The topology I propose would allow a substation to be added cheaply at intermediate points should traffic demand increase, and could be any size you wish up to the maximum rating of the rail itself, depending of what drops out of your output specification.


So best not have any electrification at all?
Because that is where this argument goes.

As the reports into problems with infrastructure projects like GWRM have stated, overly specified infrastructure is a massive problem for the railway and in British infrastructure projects more generally.

That would drop out of the detailed project specification phase. But given the low traffic density on routes that I am considering I can't see a 33kV feeder cable being a reasonable solution.

There is a maximum of four CLass 444 units west of Salisbury given the timetable and train length restrictions - that would imply a total maximum load around 8MW... which is getting on for the rating of a single 11kV feeder, let alone a 33kV one.

Many of the commenters started citing figures to justify their positions which are well away from the traffic densities on the routes I am considering for this topology.
They appear to be commenting based on third rail retaining the traditional Southern Region derived topology which takes no account for developments in controlled rectifier technology.

If they want me to run calculations for a given route, give me said project and I will try to run numbers for it.

In some cases indeed a HV fed substation would be the best solution - the key thing here is by breaking up the quanta of rectification and spreading it along the line, engineered so they can cooperate, we can drive losses down and ameliorate many of the cited problems with third rail as a solution

EDIT:

Also why does a Class 700 have so much installed power? (5000kW at rail?)
It is 12 cars long, but then the 100mph Class 707 which is five cars long and is also a Desiro city only has 1200kW installed power, both according to Siemens.
Even scaling that to ten cars only gives me ~2900kW
Is this just an AC versus DC thing?

Click to expand...

I would probably think that's 5000kW peak power.
cut that in 2/3 for RMS(*0.707 if we're going technical...but 2/3 is a reasonable approximation)
then lose a bit more through the transformer,rectifier and regulator.
that would give you about 3300kW at 750VDC.

not sure the current is correct, 4400 amps load@ 750VDC????
seems awfully high.
that would need to be spread over 3 or 4 seperate buses to make sense.

HSTEd said:

EDIT:

Also why does a Class 700 have so much installed power? (5000kW at rail?)
It is 12 cars long, but then the 100mph Class 707 which is five cars long and is also a Desiro city only has 1200kW installed power, both according to Siemens.
Even scaling that to ten cars only gives me ~2900kW
Is this just an AC versus DC thing?

Click to expand...

12 car 700s:
5.1MW on AC (traction motors are 210kW x 24)
3.3MW on DC in high supply areas (lower in Medium / Low supply areas)

The 707 has fewer (40% powered axles vs 50%) and small traction motors (150 vs 210) as it was anticipated that it only had to be better than 455s at the time of ordering (kept the cost down).
701s are 50% powered axles, 225kW traction motors and better traction motor cooling so 4.5MW on AC but still 3.3MW on DC but better regenerative braking.

HSTEd said:

Also why does a Class 700 have so much installed power? (5000kW at rail?)
It is 12 cars long, but then the 100mph Class 707 which is five cars long and is also a Desiro city only has 1200kW installed power, both according to Siemens.
Even scaling that to ten cars only gives me ~2900kW
Is this just an AC versus DC thing?

Click to expand...

hwl said:

12 car 700s:
5.1MW on AC (traction motors are 210kW x 24)
3.3MW on DC in high supply areas (lower in Medium / Low supply areas)

The 707 has fewer (40% powered axles vs 50%) and small traction motors (150 vs 210) as it was anticipated that it only had to be better than 455s at the time of ordering (kept the cost down).
701s are 50% powered axles, 225kW traction motors and better traction motor cooling so 4.5MW on AC but still 3.3MW on DC but better regenerative braking.

Click to expand...

Also, the 700 has all that power to enable it to meet the sectional running times required for the Thameslink core, that in turn enable the 24tph.

It also requires a socking great D.C. substation in the core itself. Whereas the AC is supplied from somewhat further north.

Bald Rick said:

Also, the 700 has all that power to enable it to meet the sectional running times required for the Thameslink core, that in turn enable the 24tph.

It also requires a socking great D.C. substation in the core itself. Whereas the AC is supplied from somewhat further north.

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Elstree

hooverboy said:

I would probably think that's 5000kW peak power.
cut that in 2/3 for RMS(*0.707 if we're going technical...but 2/3 is a reasonable approximation)
then lose a bit more through the transformer,rectifier and regulator.
that would give you about 3300kW at 750VDC.

not sure the current is correct, 4400 amps load@ 750VDC????
seems awfully high.
that would need to be spread over 3 or 4 seperate buses to make sense.

Click to expand...

A class 700 is as others have said 5100kW in terms of actual motor power ratings. This is a mean or average power figure. RMS applies to current or voltage, not power. Those ratings are continuous (probably 1 hour rating) and save for a couple of percent loss in the transformer and traction electronics, all of that power is available when running under OLE with 25kVac. The traction electronics losses on ac or DC are broadly similar. When on 3rd rail, like all the modern ac/DC designs, the power is severely crippled by the on-board software to cope with sub-standard power supplies. Generally not a problem on the BML as not only are all the other trains on the line similarly constrained but current collection is not always reliable at speeds close to 100mph so the extra time taken to get there is written into the timetable for the line. The class 700s operate as two six-car units each with a pantograph, transformer and inverter set. Thus their available traction power is about 1600kW each on DC.
The class 707 is configured as an ac/DC emu but fitted with lower power motors, thus their software applies less power limiting.

hwl said:

Freight when diesel is restricted in 20+ years time

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Oh, come on! How much freight do you think the North Downs Line will carry 20 years from now? How much freight between Basingstoke and Salisbury? On the Marshlink line?