Mfcttrf

The details don't matter, just that a large fraction of people have died (let's say 90%) and society has completely collapsed. It's only a year or two later, and people have started to gather together again and attempt to build communities. The leader of a large-ish (~200) band of people has a plan to rebuild as best as possible, and so plans to have everyone take up residence in a nearby city that is built near one of the US' hydroelectric power plants. This city has specifically been chosen so that the nearby hydroelectric plant can be restored and power can be available to the city.

Obviously there is a lot that can go wrong with this plan, but I'm only interested in one aspect of it. I'm handwaving away some details:

1. Assume that the survivors manage to restore the plant


2. Assume that the survivors are able to keep it functional for some extended period of time

Given those things, my question is:

Can a standalone hydroelectric plant actually be useful and provide power to a nearby city in otherwise modern USA? If not, are there any steps that could be taken to make it work?

The reason I'm uncertain is things like:

1. Our power grid is quite complicated, and it isn't obvious to me if modern day power plants can even really operate on their own


2. I'm not quite sure if power plants are actually designed in such a way that they provide their own power - I wouldn't be surprised if an external power source (even if just generators) is required at various parts


3. Presuming that the plant can operate on its own, I'm not sure if that means it can power a city that is likely connected to many other places in the grid. You might end up effectively attempting to power half the nation, which obviously isn't possible.


4. It also seems likely that the plant wouldn't be tied directly or even closely into a city anyway, and so getting power to the city would require a major overhaul of infrastructure.

In terms of power usage, the plant itself should be more than sufficient. Looking at the list of US hydroelectric plants, even the smallest generates roughly 1.3TW of electricity. We're talking roughly a couple hundred survivors, and even if they each have their own house and use electricity at standard US rates (peaking at 2kW) that still leaves room for hundreds of thousands of houses. Presumably only logistics will be an issue for our survivors for quite a while.

On September 28 2003, Italy experienced a nation wide black out.

After three hours, energy was restored in northern regions. Electricity was restored gradually in most places, and in most cities electricity was powered on again during the morning.

Energy was restored first in the northern region because there is where hydroelectric plants are located, and they could be used to power back the other plants, needing electricity to start up and operate. Ref.1 Ref.2

As long as you isolate the network that you want to supply from the network that you don't want to supply, you can use the hydroelectric plant as standalone for quite some time. (this addresses your points 2, 3 and 4). You "just" need to know the schematics of the network.

Moreover, one of the advantages of hydroelectric plants it their flexibility

Hydropower is a flexible source of electricity since stations can be ramped up and down very quickly to adapt to changing energy demands. Hydro turbines have a start-up time of the order of a few minutes. It takes around 60 to 90 seconds to bring a unit from cold start-up to full load; this is much shorter than for gas turbines or steam plants. Power generation can also be decreased quickly when there is a surplus power generation.

This is particularly important if you are supplying a relatively small city with not too much load, where load fluctuations might be relatively large.

Hydroelectric dams are definitely not maintenance-free, nor are power grids. You have three life-threatening problems for your small band of experimenters.

1) Grid power is really dangerous and complex for the inexperienced. It's quite possibly fatal for the new, inadequately equipped, untrained lineman or electrician who it trying to puzzle out the city's electrical network.

Expect several quite nasty casualties before your new settlers' figure out how to isolate their neighborhood from the larger (uncontrolled) grid and energized. Expect a lot of destroyed hardware and perhaps a few more casualties before they learn how to control phase, voltage, and amperage reliably.

2) On the dam itself, your new crewfolk are also trying to handle high volumes of high pressure water through the turbines and the spillways. Again, without proper equipment or training, expect some on-the-job casualties as they learn the hard way.

3) Finally, the dam itself requires maintenance and observation lest the structure fail catastrophically. One hopes that among the new settlers are a skilled hydrologist and a good structural engineer, because repairing a breached dam is definitely another skill you don't want to learn on-the-job...and one hopes the settlers' neighborhood isn't downstream of the breach.

Yes

With a little work it is completely possibly, you just need to cut off unused parts of the grid. This can be done by literally cutting lines or going to transmission stations a shutting down different parts. You are either using an existing microgrid or creating one by cutting apart a larger grid. Grids have to be built to be sectioned off, otherwise every downed powerline would shutdown an entire city. Many places even have existing microgrids for military bases, college campuses, and hospitals. Small power plants often have small local grids as well.

Not only can most hydroplants supply their own power most are designed to run that way, separate generators may be used for start up but the powerplant runs off its own power, it does not make a lot of sense to build parts of a power plant that need anything but the plants electricity for normal running, it just adds unneeded complexity and points of failure. There is not actually much to smaller hydro electric plants.

This does not mean it is easy, you need skilled technicians to close off the grid and to keep it running, but an existing microgrid will make it easier. You also need maintenance, which dam will determine how hard this is. Some dams need little upkeep in an off themselves at least compared to others, this is determined by size and design. There is a big difference between the hoover dam and the Rutherford Creek dam. There are actually a lot of small hydroelectric dams which are fairly low maintenance.