Transducer out of range protection for a steam turbine generator system

A control system for a steam turbine combination including at least one high-pressure turbine, a control valve for controlling the flow of steam to said high-pressure turbine, a reheater for adding thermal energy to the steam discharged by the high-pressure turbine, at least one low-pressure turbine, an interceptor valve for controlling the flow of reheated steam from the reheater to the low-pressure turbine, and an electrical generator driven by the high- and low-pressure turbines for delivering electrical power to a load, said control system including:

• main control means for positioning the control valve and the interceptor valve to match the flow of steam through the turbine with the electrical load,
• means for sensing the pressure of the steam applied to the inlet of the low-pressure turbine,
• means for sensing the electrical output power delivered to the load by the generator,
• means for generating a representation of the ratio between said sensed input pressure and said output power,
• means for closing the interceptor valve for a predetermined interval of sufficient duration to permit correction of a partial load loss when said ratio exceeds a predetermined amount, and
• means for preventing continued closing of the interceptor valve when said ratio exceeds a preselected amount for a preselected interval longer in duration than that required to correct a partial load loss.

A method of controlling a turbine system comprising:

• at least one high-pressure turbine,
• at least one low-pressure turbine,
• and an electrical generator driven by the turbines for supplying electric power to a load, said method comprising the steps of:
• generating a signal representative of pressure of the steam at the inlet of the low-pressure turbine,
• generating a signal representative of the output of the generator,
• generating a signal representative of the ratio of the steam pressure to the output power,
• terminating the flow of stream to the low-pressure turbine for an interval of sufficient duration to permit correction of a partial load loss but not of sufficiently long duration to cause the turbine to trip when the ratio of the pressure signal to output signal exceeds a predetermined amount, and
• preventing repeated termination of the flow of steam to the low-pressure turbine when the ratio of the pressure signal to the output signal remains above a preselected amount following the reestablishment of steam flow to the low-pressure turbine