| 摘要 |
A method and an apparatus for controlling feedwater flow to a steam generating device in a tripped condition of the steam generating device are disclosed. The method comprises the steps of arithmetically calculating a first forecast length of time required for the water level in the steam generating device to attain its desired normal operation level on the basis of the detected water level and the rate of variation of the water level when the detected water level in the steam generating device is lower than the desired normal operation level, the detected flow rate of feedwater is larger than that of the main steam, and the rate of water level variation is positive, arithmetically calculating a second forecast length of time required for the flow rate of feedwater to decrease to a predetermined flow rate on the basis of the detected feedwater flow rate, the detected main steam flow rate and a substantially constant rate of variation of the flow rate of feedwater when the detected feedwater flow rate is larger than the detected main steam flow rate, decreasing the level of the output signal of a ramp signal generator at a rate of variation corresponding to the substantially constant rate of feedwater flow rate variation when the time difference obtained by subtracting 1/2 of the second forecast length of time from the first forecast length of time becomes zero or negative, and selecting either the output signal of the water level controller for generating a control output signal on the basis of various input signals applied thereto including an input signal indicative of the flow rate of main steam, an input signal indicative of the flow rate of feedwater, and an input signal indicative of the water level in the steam generating device or the output signal of the ramp signal generator means, which has a lower value than the other, to deliver it as the feedwater flow rate demand signal, whereby the water level in the steam generating device is reliably stabilized at its normal operation level upon disappearance of the transient phenomenon appeared as a result of the trip.
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