Hi all;
First off, yes I know if load changes a lot, the turbine hits its limit. But for small changes within the range of the turbine’s capability, as I understand it – the turbine is kept spinning at 60Hz, and I assume a constant voltage, and more load means it works harder (burns more gas) and less load means it works easier (burns less gas).
I can equate that to riding a 1 speed bicycle where I go up hill, level, down hill, and keep pumping the pedals at the same rate. So I’m sweating like a pig going uphill and relaxing on the downhill.
But how does that work for a gas turbine? How does the demand out on the grid feed back to the turbine? Because I pictured it that the turbine sends its power out at a given Hz and V and demand doesn’t impact that at the generator, just at the end of the distribution line when the voltage drops???
thanks – dave
ps – thanks to all here that answer questions. I appreciate it very much.
Comments
I’m not an expert, but from videos I’ve watched, they get the turbine spinning as close to 60hz as possible and then basically turn it on to the grid. The power grid essentially holds it at 60hz. Basically if you let the fuel off the turbine the grid push energy into it to keep it spinning at 60hz, if you put more fuel on the turbine it’ll push energy onto the grid at 60hz.
They have a certain amount of automation in place to control the gas pedal, so if it goes down to 59.98 it will push it up a bit, and if it goes to 60.02 it will hold back. On a grid scale, this works with all the various types of power generation set to a slightly different Hz kick in/kick off limit, so they will start automatically changing based on that at different points.
The Hz of the grid is an almost immediate feedback as demand changes, so it’s really that simple. They also use very large, very heavy equipment, which acts like large flywheels helping to smooth things out, and sometimes have additional flywheel systems in place to smooth it out even more.
They also have parts of the grid that will switch off entirely based on Hz, which is usually what happens when a catastrophic black out happens.
You seem to have a better understanding of this than a 5 year old, but given the sub, I’ll give it a go:
Imagine the gas turbine is like someone pedaling a bike to make electricity. The bike has to spin at just the right speed so the lights stay on and work how they are supposed to.
When more people turn on their lights (more load), it’s like the road gets steeper. The person on the bike has to push harder (burn more gas) to keep pedaling at the same speed.
If fewer people use electricity (less load), it’s like going downhill. The person can relax and pedal more easily (use less gas) but still keeps the same speed.
A special helper called a governor watches the speed all the time and tells the person to push harder or softer so the bike always spins at just the right speed.