• SEHSR Southeast High Speed Rail Corridor

  • General discussion of passenger rail proposals and systems not otherwise covered in the specific forums in this category, including high speed rail.
General discussion of passenger rail proposals and systems not otherwise covered in the specific forums in this category, including high speed rail.

Moderators: mtuandrew, gprimr1

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  by MattW
 
No, you misread what I wrote. I didn't say use a lower voltage in the tunnel, just a lower voltage to switch. Have a step down and step up transformer of the same ratio back to back, in between, where they're linked, you have the switchgear so you don't have to directly switch high voltage.
  by electricron
 
MattW wrote: Tue Sep 22, 2020 7:02 am No, you misread what I wrote. I didn't say use a lower voltage in the tunnel, just a lower voltage to switch. Have a step down and step up transformer of the same ratio back to back, in between, where they're linked, you have the switchgear so you don't have to directly switch high voltage.
Doing so would lower the voltage, but at the same time you increase the current by the same ratio. For example, 12 kv to 600 volts is a 20 times reduction in voltage, there will be a 20 times increase in current. Low voltage, high current breakers have around four times the life expectancy or duty cycle, around 10,000 cycles.
So now, instead of replacing the breaker in 80 days, we are now replacing it in 320 days.
Better?

I do not believe people understand how much power is needed to run an ACS-64 locomotive.
Lets review the specifications:
Power Output
6,400 kW (8,600 hp) Maximum (Short-Time)
5,000 kW (6,700 hp) Continuous

P=IE. therefore I=P/E
I = 6,400,000 W/12,000 V = 533.333 Amps
I = 6,400.000 W/600 V = 10,666.667Amps

And that is just the power needed for just one locomotive.
Of course, that's was for the maximum rating, but that is what any breaker would have to handle for safety purposes. Locomotives decelerating probably will not need that much power - but locomotives accelerating will.
  by orulz
 
AREMA chart specifying clearances between wire and train or tunnel ceiling:

Image

Let's assume it's "polluted" so we need the extra clearance, and double it to find the distance from the tunnel ceiling to the train roof:

12.5kV: Normal: 15.5" Minimum 13.5"
25.0kV: Normal: 25" Minimum 20"



Vertical clearance of 1st street tunnel: 17'
Height of Stadler KISS: 15' 1"

So that leaves 23" inches.

12.5kv is no problem at all, with 7.5" of total extra clearance in the worst case - 'normal' clearances and 'polluted' conditions. 7.5" may not seem like a lot of margin, but in the world of tunnel clearances, it actually is.

In an unlikely, hypothetical future where the 1st street tunnel is electrified with 25kV instead of 12.5kV, we're short of "normal" clearances for 25kv wire in "polluted" conditions in the tunnel by 2 inches, but if we're willing to use the "minimum" values, it will fit with 3 inches to spare. Maybe the rails could be lowered a few inches by using slab tracks if those extra 2 inches are really needed. They would have to make the engineering trade-off: is it better to do an expensive, non-standard thing like slab track, or allow a sub-nominal (but still above absolute minimum) wire clearance?

Let the dog wag the tail. For VRE, get new, nice, modern rolling stock that fits, and send the non-revenue trains with superliners between Beech Grove and Lorton via some other route. Use the Cardinal's route, for example. No big deal.
Last edited by orulz on Tue Sep 22, 2020 3:22 pm, edited 4 times in total.
  by MattW
 
electricron wrote: Tue Sep 22, 2020 8:06 am
MattW wrote: Tue Sep 22, 2020 7:02 am No, you misread what I wrote. I didn't say use a lower voltage in the tunnel, just a lower voltage to switch. Have a step down and step up transformer of the same ratio back to back, in between, where they're linked, you have the switchgear so you don't have to directly switch high voltage.
Doing so would lower the voltage, but at the same time you increase the current by the same ratio. For example, 12 kv to 600 volts is a 20 times reduction in voltage, there will be a 20 times increase in current. Low voltage, high current breakers have around four times the life expectancy or duty cycle, around 10,000 cycles.
So now, instead of replacing the breaker in 80 days, we are now replacing it in 320 days.
Better?

I do not believe people understand how much power is needed to run an ACS-64 locomotive.
Lets review the specifications:
Power Output
6,400 kW (8,600 hp) Maximum (Short-Time)
5,000 kW (6,700 hp) Continuous

P=IE. therefore I=P/E
I = 6,400,000 W/12,000 V = 533.333 Amps
I = 6,400.000 W/600 V = 10,666.667Amps

And that is just the power needed for just one locomotive.
Of course, that's was for the maximum rating, but that is what any breaker would have to handle for safety purposes. Locomotives decelerating probably will not need that much power - but locomotives accelerating will.
Why would they switch under load? Yes, I know how amperage works, but arcs are formed from current, no current, no arc. The capability needs to exist, sure, but I wouldn't imagine that they would purposefully turn the power off while a locomotive was drawing, especially not drawing a maximum power.
  by electricron
 
MattW wrote: Tue Sep 22, 2020 10:13 am Why would they switch under load? Yes, I know how amperage works, but arcs are formed from current, no current, no arc. The capability needs to exist, sure, but I wouldn't imagine that they would purposefully turn the power off while a locomotive was drawing, especially not drawing a maximum power.
They would not decide to switch it off under load, that would stop the train in the tunnel blocking the track. But the circuit breaker has to be sufficient capable to do so, at 3 times of that at a minimum for an overload condition, like a failed transformer or motor short circuit in the locomotive, or a fallen tree over the catenary for safety reasons. Otherwise the breaker would weld shut and you would have to kill an even larger section of track to deenergize the failed component.
Circuit breakers must be capable to handle fault currents, not normal operating currents.
  by mtuandrew
 
orulz wrote: Tue Sep 22, 2020 10:03 amLet the dog wag the tail. For VRE, get new, nice, modern rolling stock that fits, and send the non-revenue trains with superliners between Beech Grove and Lorton via some other route. Use the Cardinal's route, for example. No big deal.
I appreciate the chart.

If you can get Virginia to order some corridor-sized stock or something slightly larger (like KISS) I’d be just fine with that. Don’t expect VRE to electrify anytime soon though - whatever they get would have to be diesel-for-now. The galleries stay unless the Feds give them a tasty rolling stock grant like they did for North Carolina; electrifying First Street Tunnel would be a good reason for the Feds to give such a grant.

Also, the Cardinal route goes via the First Street Tunnel too :wink: you’ll have to send your Superliners via Benning Yard and the Virginia Avenue Tunnel.
  by orulz
 
The Cardinal does use 1st street, but not in that direction. If the premise is that the only time Amtrak sends Superliners through 1st street is non-revenue moves of equipment between Beech Grove and Lorton, they should just send them via the Cardinal route, drop them off somewhere near Alexandria, and pull them down to Lorton from there. No 1st street tunnel needed.

I'd like to know if Stadler is interested in making an electro-diesel version of the KISS. They already do this with the FLIRT.
  by electricron
 
orulz wrote: Wed Sep 23, 2020 8:22 pm I'd like to know if Stadler is interested in making an electro-diesel version of the KISS. They already do this with the FLIRT.
If Stadler were to be given an order for a DMU/EMU version for a KISS, they would probably be willing to design one and build one. To date, no one has.
  by mtuandrew
 
I’d like to see Amtrak buy shorter, 125 mph capable bilevels with high & low platform capability. 15’ 6” (8” shorter than the Supers) should be short enough for First Street yet tall enough for bedrooms. (Still trying to figure out a way to stuff bedrooms in a 14’ 6” envelope without everyone being crammed like sardines.)

Sell off the Superliners to some other operator.

Sorry - I took us off topic here, let’s finish up this sidetrack and get back to SEHSR.
  by Literalman
 
The discussion of VRE electrification seems to overlook the Manassas line (unless I overlooked something myself). I imagine that VRE would choose to remain all diesel rather than have an electric fleet and a diesel fleet for the two lines. Electrifying the Manassas line seems beyond unlikely because (1) west of Alexandria it's owned by Norfolk Southern and (2) it has an average of 11 or 12 trains a day (16 each weekday, none on weekends).
  by KTHW
 
Manassas line is actually perfect for VA to buy. It’ll never see high speeds due to its curves, but NS doesn’t really run a lot of trains on it, and the few that do run mostly go to shrinking industrial areas in Alexandria. Electrifying it would actually make a lot of sense so cars can accelerate in and out of the curves faster.
  by mtuandrew
 
KTHW wrote: Mon Sep 28, 2020 7:37 pm Manassas line is actually perfect for VA to buy. It’ll never see high speeds due to its curves, but NS doesn’t really run a lot of trains on it, and the few that do run mostly go to shrinking industrial areas in Alexandria. Electrifying it would actually make a lot of sense so cars can accelerate in and out of the curves faster.
As a Virginia taxpayer I wouldn’t be opposed - however, that’s outside the scope of this thread. Check out this thread in DC/MD/VA Passenger Rail: viewtopic.php?f=64&t=151257
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