nomis wrote: ↑Sat Jul 09, 2022 8:02 pmWhat would you say an adequate acceleration and deceleration curve look like?
For reference, the Rotem SL-V’s for SEPTA hit their target 3 mph/s on both accords & still able to stretch its legs to 95 mph out of 100mph rated between stations on the “Trenton Line” side of the NEC.
The LIRR Today wrote about this a while back. 3mph/s, or 4.4ft/s^2 is very good. Modern EMUs should be able to do 4ft/s^2, and many subway/rapid transit lines do. The M-7 cars could do 3ft/s^2 or about 2mph/s if LIRR had enough power to run them at full power, not the 1.5ft/s^2 or 1mph/s that their inadequate power infrastructure can handle.
Top speeds don't really matter much for commuter/regional rail, maintaining track speeds above 80mph usually doesn't help much purely for time, although when running on the NEC, or really anywhere, it would probably make for a smoother ride and less wear and tear, and why not?
I can't get a good measure on how fast the HSP-46s can accelerate, but based on videos, I'd guesstimate it somewhere around 1ft/s^2. It's probably higher once the thing get loaded up, since that takes quite a while of going basically nowhere.
Deceleration should be similar on about anything, although EMUs could go into full regenerative braking, and use their IGBT inverters to brake at 1000 HP/car right down to a dead stop without using their mechanical brakes if they were set up to do so, whereas diesel or electric push/pull has to use mechanical brakes.
It's probably a minor improvement, but I'd think that taking the human engineer out of the equation and programming the trains to run themselves would speed it up a bit, as they could wait until the last calculated second to go into full regen braking. I do have to wonder if Amtrak or any of the commuter agencies have tested automated operations, as ACSES provides all the inputs required to do so, it would just be a matter of writing the software to do so, and allowing the PTC not just to decelerate/brake and notch down, but to accelerate. Full length high level platforms speeds thing up too, as they don't have to get the spotting as exact as when using a single mini-high.
Disney Guy wrote: ↑Sun Jul 10, 2022 10:45 amDo electric railroads customarily "bring their own juice"? Example: The T having feeders bringing multi thousand kilovolt power through the subway and out the Green Line right of way to the Cook St. substation near Newton Highlands? As opposed to getting the (originally 13.8 KV, maybe more now) powerfrom the nearest Eversource substation in Newton. Or have both sources for redundancy in case of some kinds of power outages? (The 600 volt traction power could (at least back in the 1960's) adequately serve Riverside from Cook St. but would suffer too much voltage drop losses coming all the way from So. Boston.)
If I recall correctly , the D-Riverside line station lighting was powered from the local utility lines.
FRA heavy rail is a different animal. The ex-Reading SEPTA system has a central converter to convert from 60hz transmission power to 25hz 11/22kV, while the Amtrak ex-Pennsylvania system has a series of converters to convert 60hz transmission to 138kV 25hz that then has substations to provide traction power. The Amtrak 12.5kV/60, MN 12.5kV/60 and Amtrak 25kV/60 systems all have a series of substations where they are fed at transmission voltage, and they step down to the traction power voltage.
The Amtrak 25kV/60 system's higher voltage and use of 50kV split phase allows it to span fairly long distances between substations, but still provide redundancy in case power is cut to one, those sections can be run through paralleling stations to feed the section from either end. The 25kV/60 system has adequate capacity for the modest CDOT Shore Line East operations that just recently electrified, and was built to be able to be upgraded for the T to operate electric on the Stoughton and Wickford Junction lines.
FRA heavy rail consumes too much power to be fed from distribution voltage*.
*MN did feed part of the New Haven Line from a ~13kV distribution circuit via FrankenTransformer briefly in September 2013 after Backhoe Bob cut power to a critical section of the New Haven Line/NEC between New Rochelle and Stamford while their redundant power feed was also out of service. Through trains had to go into the section fed via FrankenTransformer at a moderate speed, and were able to use it to get through the section at low power, but not accelerate. I can't remember if they had local service accelerate very, very slowly in the section, or if they covered it with limited diesel dual-mode service.
EDIT: All electric railroads built pre-WWII had their own distribution systems and transmission as needed, as there wasn't a power grid in the way we think of it today, or with the necessary power available. Only modern systems like the Amtrak Shore Line or Denver RTD were built based on the availability of transmission-level grid power. The PRR and Reading systems still do their own distribution and transmission (PRR) even though they are mostly fed from commercial power instead of their own generating stations. The MN/Amtrak 12.5kV/60 systems were converted from the New Haven Railroad's coal fired plant at Cos Cob in 1982 to 60hz grid power, and now the ROW above the tracks is leased out to Neversource/UI/whomever for regular power grid transmission lines at 115kV.