System and method for operating a steam turbine with capability for

Abstract

A steam turbine is provided with an electrohydraulic control system having an automatic control which includes a digital computer and further having a manual backup control for operating the turbine on automatic or operator switchover to backup control. The automatic control includes control elements and logic elements associated with valve control loops coupled to the turbine and high and low limits and other constants, setpoints and other parameters are characteristic to these control and logic elements and the interrelations among them and the turbine. A switch arrangement is provided for generating parameter value signals corresponding to changed values for the system parameters and for coupling the parameter value signals to the automatic control system where they are registered. The automatic control system is structured to reject invalid parameter value changes and to register only those parameter value changes which can be validly entered as part of the system structure. Once the switch arrangement is activated to initiate a parameter change, the automatic control system bumplessly rejects to the manual backup control so that the control configuration can be restructured while on-line turbine operation continues without substantial interruption. Once the parameter change process is completed, return can be made to automatic operation.