Hi,

I would like to know what exactly happens when we change the speed control of Steam Turbine for 600 MW subcritical Power Plant from MSV to GV?

I am a simulator instructor and many times asked this question.

 

Hi,

I would like to know what exactly happens when we change the speed control of Steam Turbine for 600 MW subcritical Power Plant from MSV to GV?

I am a simulator instructor and many times asked this question.

It is called valve transfer with or without bypass in service, where bypass I/S is more difficult for control design. Before the valve transfer, a steam turbine generator set should be synchronised and the initial load completed (Normally, 10% of MCR). Operator manually initiates a FA/PA transfer auto interlock. Then, the initial gov. close-in interlock should be activated to close GV, while RSV-BV and TSV-BV valves are further open to maintain the output MW at its set point until TSV outlet pressure/TSV pressure actual > 85% (if the bypass system is in service, it would be a lower limit, e.g., 70%). the pressure ratio >85% means gov in control and a fast open request is initiated to fast open these BVs to 100% open. Pleaes note, before the vlv transfer, gov is fully opened via setting the load limiter to 100%. With bypass I/S, RSV-BVs are responsible for load control while TSV-BVs move proportionally with the RSV-BVs.