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Comment by renewiltord | Hacker News Reader

This might sounds dumb, but why not extension cables for the second engine that was providing zero power.

I grew up in that town. To reach the high-school from the track, you have to cross an overpass. They were concerned about the weight of the train. The school is is about 1.4 km from the overpass.

If the overpass was the issue you'd think they would have realized that before moving the second locomotive at all. One would assume you'd at least plan out the route in advance.

Oh thanks. Fair enough.

You gotta have some real big cables to avoid transmission loses.

Ah, just seemed surprising they had all these parts to step down the voltage and everything but didn't have power cables. But I guess it is what it is.

The distribution infrastructure for distances above a few hundred meters(yards) typically uses 10 or 30 kV, and the former is fairly easy for pantograph-powered locomotives. So if the locomotive can optionally use a pantograph instead of it's diesel (tunnels and urban areas on the east coast come to mind), it has a transformer between the low-voltage traction motors / diesel generator rail and the pantograph rail (15~25 kV, typically).

The alternator and transformer don't care about the lower voltage, except that their current capability won't change much (so you loose power capability).

So I'd assume they should be able to use existing power lines from the other side of the overpass to the school, possibly after isolating that segment from the rest of the grid.

This might also connect some other buildings, but typical transformer ratings here (DE, urban, residential; are a few hundred kVA. So

(If you don't know what kVA means, "kW felt by wires/ transformer/generator, but not the diesel" is a rough summary sufficient for this scenario.

(Don't worry, it's neither wrong nor misleading. If you disagree with that statement, elaborate and feel free to downvote.))

Fascinating. Thanks for sharing.

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