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HydroElectric Equipment

Zephyr7

Registered
I wish I’d seen this thread earlier! I love micro hydro setups!

Everyone is correct that you control the speed primarily with a valve that controls the water flow to the turbine, but in microhydro setups it’s also common to have a load control that keeps the generator operating at a fixed load. This allows for electronic frequency control with a fast response that would not be possible using a mechanical valve. These systems work by using a multi step resistive load bank and a bunch of relays or a thyristor (like a triac) to make an adjustable load. The controls are configured so that any power not consumed by the real load is dumped into the resistive load bank. If you have 2kw of real load, and a set 5kw load for the generator, the resistive load bank would be set to consume the extra 3kw. You get better response that way since you can more rapidly vary the load of the load bank than you can vary the flow of water and speed of the turbine.

That transformer might be used to step the generator voltage up to 480v for transmission back to the house. This would help a lot to keep volt drop under control. If that’s the case, there is probably a matching transformer back at the house.

I doubt this was setup for grid tie operation. All the synchronization issues on a small scale would be a lot of hassle. I’d expect the system is setup to run the house as an isolated load. That’s how I’d do it anyway.

I would absolutely try to get this system running again. You have a VERY interesting system here! I’d love to build something like that myself. I have several small streams on my property, but none have much drop so I’d have to use “run of the river” turbines which give much less power out.

Bill
 

Birken Vogt

Registered
Those stories have been an inspiration for us. Whenever people need large equipment and machinery moved around they call us. Although not quite on that scale. Sometimes we wonder if we are charging enough money for these jobs.
 

Zephyr7

Registered
Well Birken, it’s easy to test your theory: charge more and see if you keep getting jobs :)

I’ve run into that myself doing consulting work. There aren’t many people who do what I do, but it’s tricky to find the right balance between charging what you’re worth and charging what customers expect to pay.

Bill
 

Wayne 440

Registered
...Whenever people need large equipment and machinery moved around they call us....Sometimes we wonder if we are charging enough money for these jobs.
If you are wondering about your rates, you are almost certainly low. IF you show up when you say you will and get done on time, you can probably raise your rate by 20% without affecting your volume.
 

DKamp

Registered
...Everyone is correct that you control the speed primarily with a valve that controls the water flow to the turbine, but in microhydro setups it’s also common to have a load control that keeps the generator operating at a fixed load. This allows for electronic frequency control with a fast response that would not be possible using a mechanical valve...

These systems work by using a multi step resistive load bank and a bunch of relays.......

...I doubt this was setup for grid tie operation. All the synchronization issues on a small scale would be a lot of hassle. I’d expect the system is setup to run the house as an isolated load.
Bill... if it's grid-tied, there's no need to control ANY of that... at all. All one has to do, is spin the generator up to synchronous speed, and throw the big switch. Once a synchronous generator is connected to the grid, it will either motor (consuming power from the line) or drive (push generated current INTO the line). The only thing that will ever cause it to lose synchronization with the line, is if the generator burns up, or the connection is broken.

If synchronization seems really difficult and expensive, it's not.

I had opportunity to perform a demonstration on a fault recording system using a small 1920's era 200kw hydroelectric plant, and the synchronization equipment consisted of one small knife switch, three large (1/2 ohm or so) resistors, one big knife switch, three 100w lamps, and a place to stand.

Between the generator and line are three resistors, one on each leg. In series with the three resistors, is a small knife switch.
Bypassing the three resistors and small knife switch, are three light bulbs, in parallel with one big knife switch.

With the grid line live, the starting process is easy, and can be done in several different ways... regardless of wether the generator is stopped or spinning. First, is to look at the three lamps- they'll all be illuminated, and fairly bright... If not, replace the 'bad' bulbs. They indicate current flowing between the grid, and the generator. Start by throwing the small switch... this flows a limited amount of current into the generator, and starts it rotating. the lamps will dim considerably. As it speeds up, the lamps will start to brighten a bit, and then (as it gets closer to synchronous speed), they'll start to dim again. Eventually, they'll get just barely glowing enough to notice, throw the big switch. Now you're synchronized, but MOTORING.

Now open the penstock valve.

IF you have a metering system between the generator and line, you'll see that in motoring mode, current is flowing INTO the generator. Once penstock flow is pushing the generator, current will flow OUT of the generator, into the grid. In motoring, the current waveform is LAGGING the grid line, but in GENERATING, it's LEADING the line.

The generator CANNOT spin faster than the line... flowing more penstock pressure and volume will NOT magically force the generator to exceed line speed... instead, what happens, is that the applied voltage to the local grid connection will rise as a result of applied outgoing current. If one puts enough shaft horsepower in it to cause the generator to output at a frequency HIGHER than the grid to which it's connected, the result will be a burning generator, as this is insufficient generator capacity for the shaft horsepower being applied. You'll get a blown fuse or line breaker.
 
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