Northeast Corridor railroad power

I was curious about the power for the Northeast Corridor railroad. I noticed the railway and its associated power lines from I-95 north of
Philadelphia. I know the railroad power is 25 Hz, not 60 Hz, so it makes sense to have its power lines closely following the railroad for its entire length from NYC to Washington. What surprised me was how substantial the power lines seemed to me. It looked like they would be enough to power a medium sized city. How much power does the Acela trains and the others really use?
How is the power configured? I know the trains themselves use 12kV. Is this single phase AC?
The power lines seemed to be in 3 groups. All had the same size insulators, which were rather substantial, and I'll guess they're good for at least 150kV. One group was 3 conductors, which seem to be standard 3 phase. The other two groups were 4 conductors each, not 3. What are they carrying? I suppose it could be "4 phase power", 4 conductors at 0, 90, 180, 270 degrees phase angles, a variation of 90 degree 2 phase power. Or are they 4 (8?) single phase circuits? I thought I saw a railroad overpass paralleled by towers with only 2 conductors of the same size as the mainline, but am not sure.
What voltage do the HV circuits run at? What kind of configuration do the 4 conductor groups use? Why the apparent large capacity?
How is all this powered? I've read there's a hydroelectric facility in Delaware or Maryland. Others? I'll assume there are converter facilities taking power from the 60 Hz grid somewhere. Are there any non-railroad loads on the 25 Hz "grid" at all?
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