JPS57173508A - Control device of turbine bypass - Google Patents

Abstract

PURPOSE:To prevent evaporation in an economizer outlet at single operation of a turbine in a plant, by determining saturated pressure from fluid temperature in the economizer outlet, generating a setter signal, with an enough margin not to cause boiling even in a transient state, and controlling inlet pressure of the turbine to set pressure through said setter signal. CONSTITUTION:At normal operation, the value of a bypass setter 12 is added to a pressure signal, from a pressure transmitter 8 of main steam in a turbine inlet, in an adder, introduced to a comparator 15 through a side A of a signal switch 14, and compared with an actual pressure signal from the transmitter 8, in accordance with this compared result, to control a turbine bypass valve 9. On the other hand, at single operation in a plant or run back time, the signal switch 14 is selected to a side B, and a pressure setter signal, determined not in an evaporation range, is fed from the output signal of an economizer outlet fluid temperature transmitter 2 by a signal converter 19 to a low signal selector 20. Then the signal is compared with the signal from said transmitter 8, and whichever one smaller of the signals is fed to the comparator 15, here in accordance with the compared result, said valve 9 is controlled.