Overspeed protection control arrangement for a steam turbine generator control system

Claim 1

An improved OPC arrangement for a turbine control system having at least one central controller in two-way digital data communication with a plurality of motive fluid admission valve control circuits for controlling motive fluid admission to the turbine, comprising: (A) at least three OPC circuits each including programmable digital computer means in two-way digital data communication with said controller; (B) at least three speed transducers positioned to derive respective output signals indicative of turbine shaft rotational speed; (C) each of said OPC circuit including circuit means operable to convert a respective one of said speed transducer output signals to a pulse waveform of a frequency greater than the frequency of the received speed transducer output signal; (D) means for counting the pulses of said waveform and for sampling the count in repetitive predetermined periods of time for transfer to said digital computer means; (E) said digital computer means being operable to calculate turbine speed and provide a turbine speed signal (RPM), in response to said counts transferred to it; (F) means for providing said turbine speed signal to said other OPCs, as well as said central controller; (G) said digital computer means being responsive to RPM signals received from other OPCs to validate its own RPM signal if it is in agreement with a predetermined number of other received RPM signals.