Could anyone please clear this up for me? Say the turbine is outputting 25MW and the circuit breaker for whatever reason opens. Now you have this massive amount of energy going to wind your turbine out.

What prevents this from happening?

Thanks

 

The Subject of this thread is regarding the effect on TA from breaker opening under power, but TA is not defined in the body of the thread. TA can mean Technical Adviser, or it can mean Trip Anticipator, or it can mean something else.

The torque produced by a turbine driving a generator is controlled by some type of valve to limit the amount of energy (fuel or steam or water) to the turbine (combustion or steam or hydro).

So, when a breaker is opened under power it's extremely important to either, (1) make sure the control valve closes extremely quickly to limit the energy flowing into the turbine, or, (2) close the stop valve (usually upstream of the control valve, but may be downstream, too) to shut off the flow or energy into the turbine to prevent excessive overspeed.

Usually when a "load rejection" occurs (load rejection is the common term for the generator breaker opening under load) there will be some overspeed of the turbine, simply because of the amount of energy trapped between the control and/or stop valves (which is why they are usually located very close to the turbine). Some steam turbines even have intercept valves which open to direct steam away from the turbine to help reduce the magnitude of the overspeed. Some hydro turbines have bypass valves to do the same thing--to help prevent overspeed and to protect the turbine and the penstock.

If left unchanged, yes--there will certainly be an overspeed condition, which should result in a closure of the stop valve(s) to prevent any more energy from entering the turbine. But, the idea is to try to prevent ever reaching overspeed by limiting the energy input sufficiently in the first place on a load rejection or breaker open event.

Finally, some large turbine do have Trip Anticipators that actually look at current flow and can very quickly determine that current flow has stopped and will activate measures to prevent overspeed of the turbine-generator.

Hope this helps!

 

As CSA questioned, what is the "TA" you are asking about. some other pertinent information would be the type of turbine (ST/CT?) and the full load rating.

as CSA explained the unit will accelerate upon load rejection, that accel rate depends upon of the % of full load (actually load versus unit inertia. So if the load was 25MWs for a 1000MW high inertia unit, the rate of speed increase would be several seconds till overspeed trip is approached (if the governor is failed). however, if the max load is 25MWs, the overspeed trip would be exceeded in about 1 second.

IF your question was concerning a Trip Anticipator, some more info about the remainder of your controls would be needed for proper explanation.