QueensCurve
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It would be.
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Distributed rectification for third rail
- Thread starter HSTEd
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It would be.
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HSTEd
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I am still waiting for the ORR to get back to me, although they have acknowledged the FOI.
In the meantime I did some more research into ~10kV Solid State Transformers and found this study.
For a fully reversible, fully controllable 1000kVA power converter from 10kV AC to ~800Vdc they want something like $34k.
Although that does not include any auxiliaries or buildings or what not it shows how far industrial rectifiers have come. And connects directly to a HV supply (through an appropriate circuit breaker or RMU or similar).
SO I decided to go a bit nuts and assume 1000kW substations, using similar ~855Vdc topping voltages to my previous calculation. But this time including a worst case load of 2 12-car Class 319 units accelerating at maximum power as they pass.
If we set a rail voltage of 775Vdc and 6000kW - that gives us 7742A.
3871A in each direction - 500m to the first substation produces a 25.2V drop (using my earlier assumptions).
That gives us ~801V at the first substation, current output of 1248A giving us a 2624A spillover.
2624A over the kilometre to the second substation gives us a 34V drop - that takes us to 835V at the second substation.
The second substation can output 1198A @ 835V - giving us a 1425A spillover.
1425A over the kilometre to the third substation produces an 18.5V drop, giving us something like 854V @ the third substation.
AT 854V the substation can output 1171A - giving us a 254A spillover to the fourth substation.
254A spillover to the fourth substation produces a 3.3V drop, giving us a final voltage of ~857.5V. (Lucky guess on the at-train voltage to get so close to my 855V target).
That translates to a total at-substation power of 6256kW for 6000kW delivered, giving us a ~96% efficiency.
And the fourth substation is under 50% load so it means an 8km spacing can be used. Which is at least 4-5trains per hour.
So it can support at least 4-5 trains (probably significantly more) per hour per direction, with every train formed of 12-car 319s. With a peak-load efficiency of over 95%
Although this required a voltage rise in the running rails of 61V, which is within the allowable specification for main line railways of 120Vdc but is a little troubling. I would probably want to attach an aluminium bus bar (for example made out of worn out composite conductor rails) in parallel with the running rails. Which would cut that rather drastically. But that would have to be weighed against the cost of simply shrinking the substation spacing some more. It is acceptable but it is not the best in my opinion.
Either way that is some crazy performance, and diversity requirements in the 11kV supplies and the costs of the supply become important at that level.
I think I underestimated the amount of advance in AC-DC converter technologies recently.
In the meantime I did some more research into ~10kV Solid State Transformers and found this study.
For a fully reversible, fully controllable 1000kVA power converter from 10kV AC to ~800Vdc they want something like $34k.
Although that does not include any auxiliaries or buildings or what not it shows how far industrial rectifiers have come. And connects directly to a HV supply (through an appropriate circuit breaker or RMU or similar).
SO I decided to go a bit nuts and assume 1000kW substations, using similar ~855Vdc topping voltages to my previous calculation. But this time including a worst case load of 2 12-car Class 319 units accelerating at maximum power as they pass.
If we set a rail voltage of 775Vdc and 6000kW - that gives us 7742A.
3871A in each direction - 500m to the first substation produces a 25.2V drop (using my earlier assumptions).
That gives us ~801V at the first substation, current output of 1248A giving us a 2624A spillover.
2624A over the kilometre to the second substation gives us a 34V drop - that takes us to 835V at the second substation.
The second substation can output 1198A @ 835V - giving us a 1425A spillover.
1425A over the kilometre to the third substation produces an 18.5V drop, giving us something like 854V @ the third substation.
AT 854V the substation can output 1171A - giving us a 254A spillover to the fourth substation.
254A spillover to the fourth substation produces a 3.3V drop, giving us a final voltage of ~857.5V. (Lucky guess on the at-train voltage to get so close to my 855V target).
That translates to a total at-substation power of 6256kW for 6000kW delivered, giving us a ~96% efficiency.
And the fourth substation is under 50% load so it means an 8km spacing can be used. Which is at least 4-5trains per hour.
So it can support at least 4-5 trains (probably significantly more) per hour per direction, with every train formed of 12-car 319s. With a peak-load efficiency of over 95%
Although this required a voltage rise in the running rails of 61V, which is within the allowable specification for main line railways of 120Vdc but is a little troubling. I would probably want to attach an aluminium bus bar (for example made out of worn out composite conductor rails) in parallel with the running rails. Which would cut that rather drastically. But that would have to be weighed against the cost of simply shrinking the substation spacing some more. It is acceptable but it is not the best in my opinion.
Either way that is some crazy performance, and diversity requirements in the 11kV supplies and the costs of the supply become important at that level.
I think I underestimated the amount of advance in AC-DC converter technologies recently.
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