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Comment by throw0101c | Hacker News Reader

HVDC facilities look like something out of a scifi movie:

* https://new.abb.com/news/detail/19701/abb-wins-600-mw-hvdc-o...

... meanwhile, it's hard to believe that Japan still runs two separate grids at two separate frequencies. Seems like it'd be worth sorting out a transition plan instead of building that sort of facility, and (presumably) a bunch of others just like it.

I think they might want HVDC either way, and since they’ll have to convert from DC to AC locally anyway, maybe it isn’t so bad?

It does seem a little weird though.

It’s not worth the eye watering amount of money it would cost to change. It took nearly seventy years to transition users off the much smaller NYC DC grid, which was obsolete in the 1920s!

On the contrary, as inverters and HVDC get cheaper, large synchronous grids are less worthwhile. Smaller grids are more resilient and easier to recover; that's the direction we're headed in, with plans to decouple some of these continental grids.

Any time I see rooms like this, I think to myself "Do not touch ANYTHING in here"

Indeed, they do. The Wikipedia page photos are some of my favorite photos of power tech.

Another thing that made a really strong impression was visiting a power dam and realizing that it was almost dead quiet while an enormous amount of power was being generated. Just a slight hum and a vibration in the floor, that was all.

But if those rotors were even a few grams out of balance, you'd feel it. Also, if something went wrong with the valves, you'd also hear it. Right before you drowned and/or were killed by flying concrete. Moving water does NOT like to stop.

Yes, the water hammer from a major dam must be quite impressive if you try to contain it by main force rather than to reduce the flow gradually.

I've seen some videos which show, if I understood the description correctly, chambers which contain the overpressure from these water hammer events. For instance: https://www.youtube.com/watch?v=fJVBlhgt9j8

That's impressive. I've seen a 2" butterfly valve attached to a stepper motor blown clear off the tube it was on because it closed too quickly. Oops... expensive lesson.

Here's a documentary on one disaster: https://youtu.be/OjMtbkFF3RM

75 deaths. RIP.

Oh, that's ugly. Not to be callous: but it could have been much worse still, in spite of all of the failing safety systems. The dam itself could have failed and the downstream effects would have been on a completely different level.

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