JPH0692808B2 - Moisture separation reheater controller - Google Patents

Description

The present invention relates to a controller for a moisture separation reheater in a steam turbine plant, and more particularly to a controller for a moisture separation reheater when a plant starts / stops or when an abnormality occurs. The present invention relates to a control device for a moisture separation reheater that also considers protection of a low pressure turbine as well as a separation heat reheater.

[Conventional technology]

FIG. 3 is a diagram showing a main system of a nuclear power plant using a conventional moisture separation reheater control device, in which steam generated in the reactor 1 has a flow rate depending on a load in the main steam control valve 2. It is controlled and flows into the high pressure turbine 3. High pressure turbine 3
Since the pressure and temperature of the steam that has been used for the work have decreased and the degree of wetness has increased, the moisture is separated by the moisture separator 4, and the steam is further separated by the first-stage reheater 5 and the second-stage reheater 6. After exchanging heat with the heated steam, it flows into the low-pressure turbine 7. The steam that has worked in the low-pressure turbine 7 is guided to the condenser 8, and the work given to each turbine is converted into electric power by the generator 9. The moisture separation heater 10 that contributes to improving the thermal efficiency of the plant is composed of the moisture separator 4, the first-stage reheater 5 and the second-stage reheater 6, and serves as heating steam for the first-stage reheater 5. Is the high pressure turbine bleed air, and the main steam generated from the reactor 1 is used as the steam source of the second stage reheater 6.

[Problems to be solved by the invention]

By the way, considering the operation of the moisture separation reheater 10 in each load zone, in the first stage reheater 5, the cycle steam from the high pressure turbine 3 which is the steam to be heated and the high pressure which is the first stage heating steam. Since each pressure of the turbine bleed air is proportional to the load, the temperature difference between the inside and outside of the heat transfer tube is not so large as to cause a problematic thermal stress.

However, the pressure of the cycle steam flowing to the second-stage reheater 6 is proportional to the load, but the main steam pressure of the second-stage heating steam is constant as shown by the dotted line in FIG. In that case, the temperature difference between the inner and outer surfaces of the heat transfer tube becomes large and excessive thermal stress occurs.

To solve this problem, generally, as shown in FIG. 3, a control valve 11 for adjusting the amount of steam is provided in the second stage heating steam pipe, and the control valve 11 is controlled by the moisture separation reheater controller 12. By the control, the second stage heating steam pressure is controlled to be a linear function of the load in the low load zone as shown by the solid line in FIG. As the load signal, the high pressure turbine exhaust pressure detector 13 and the generator output detector 14
Signals such as are often used.

However, although this method can protect the second-stage reheater from thermal stress, the moisture separation reheater body is subject to heat stress due to the steam temperature difference between the inlet and outlet cycles of the moisture separation reheater, and the low pressure turbine. With respect to, there is no protection function against the thermal stress generated when the steam temperature at the outlet cycle of the moisture separation reheater suddenly changes. Therefore, in the event of sudden change in load, abnormal pressure control, etc., if the steam temperature difference between the inlet and outlet cycles of the moisture separation reheater or the rate of steam temperature change at the outlet cycle of the moisture separation reheater becomes excessive, the moisture separation reheat There was a problem that the life of the main unit and the low-pressure turbine was greatly shortened.

Therefore, an object of the present invention is to provide a control valve that normally controls the second-stage heating steam pressure so as to be a linear function of the load, to a moisture separation reheater inlet / outlet cycle steam temperature difference or a humidity separation outlet cycle steam. It is an object of the present invention to provide a controller for a moisture separation reheater, which preferentially outputs a control signal such that those values remain within the limits when the rate of temperature change exceeds the limits.

[Structure of Invention]

(Means for Solving the Problems) The present invention relates to a controller for a moisture separation reheater having a two-stage reheater using main steam and high-pressure turbine bleed air as respective heating sources. A control valve for adjusting the amount of heating steam flowing into the second-stage reheater is provided at the inlet of the heater, and the heating steam pressure of the second-stage reheater is determined as a function of load. And a controller that outputs a valve opening command signal to the control valve, and a moisture separation reheater inlet / outlet cycle steam temperature difference and low-pressure turbine inlet steam temperature change rate are compared with their respective limit values. And a selector that compares the output signals of these controllers with the valve opening command signal to select a high value or a low value and outputs a final valve opening command signal. It is characterized by

(Operation) In normal times, the control valve is controlled so that the pressure of the steam heated by the second-stage reheater becomes a linear function of the load. However, when the load changes suddenly, the moisture separation reheater inlet / outlet cycle steam When the temperature difference or the low-pressure turbine inlet steam change rate exceeds the set value, the opening of the control valve is controlled, the inflow amount of the second-stage reheater heating steam is controlled, and the moisture separation reheat is controlled. The inlet / outlet cycle steam temperature difference and the low-pressure turbine inlet steam temperature change rate are adjusted to be within the set values. And, thereby, the moisture separator main body and the low-pressure turbine can be protected from the lifetime consumption due to the thermal stress generation.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a configuration diagram of a moisture separation reheater control device to which the present invention is applied, and FIG. 2 is a main system diagram of a nuclear power plant to which the present invention is applied.

The cycle steam generated in the nuclear reactor 1 and worked in the high-pressure turbine 3 is guided to the moisture separation reheater 10 and the moisture separator 4, the first
After being heated by the stage reheater 5 and the second stage reheater 6, it is introduced into the low-pressure turbine 7 where work is performed. By the way, the main steam generated from the nuclear reactor 1 is used as the second stage heating steam, and the steam is controlled by the control valve 11.

By the way, the moisture separation reheater control device 12 for controlling the opening degree of the control valve 11 includes a second stage heating steam pressure detector 15 for detecting the steam pressure at the inlet of the second stage reheater 6. Detection signal from the high pressure turbine exhaust pressure detector 13 for detecting the exhaust pressure of the high pressure turbine, and the low temperature turbine inlet steam temperature detector provided at the low pressure turbine inlet portion.
The detection signals from 16 are input respectively.

Therefore, the signal from the high-pressure turbine exhaust pressure detector 13 is first converted into a load signal by the function generator 17 and input to the next second function generator 18, where the temperature limitation of the second stage reheater 6 causes It is converted into a pressure setting signal which is determined as a linear function of the load. Then, this pressure setting signal is input to the subtractor 19.

A detection signal from the second stage heating steam pressure detector 15 is also input to the subtracter 19, and the deviation between the pressure setting signal and the signal from the second stage heating steam pressure detector is calculated there. Then, it is input to the PID controller 20 and the valve opening command signal is calculated. The valve opening command signal calculated by the PID controller 20 in this way is output as a control signal to the control valve 11 via the high value selector 21, the low value selector 22, and the low value selector 23.

The signal from the high-pressure turbine exhaust pressure detector 13 is also applied to the function generator 24, converted into the high-pressure turbine exhaust temperature, and input to the subtractor 25. The signal from the low-pressure turbine inlet steam temperature detector 16 is also input to the subtractor 25, where the moisture separation reheater inlet / outlet cycle steam temperature difference is calculated, and the next subtractor 26 inputs the moisture separation reheater inlet / outlet. Cycle steam temperature set value
The deviation from 27 is calculated and output as a valve opening command signal by the PID controller 28 to the low value selector 23, where it is compared with the valve opening command signal to select the low value.

Further, the change rate of the low-pressure turbine inlet steam temperature is calculated by the differentiator 29, and the low-pressure turbine inlet steam temperature increase rate limit value 32 and the low-pressure turbine inlet steam temperature decrease rate limit value 33 are respectively calculated by the subtractor 30 and the subtracter 31. The deviation is calculated, and the valve opening command signals are calculated by the PID controller 34 and the PID controller 35, respectively, and the former is input to the low value selector 22 and the latter is input to the high value selector 21, and the PID controller 20 Is compared with the output signal from.

This control circuit normally outputs a control signal from the PID controller 20 to the control valve 11, but if the moisture separation reheater inlet / outlet cycle steam temperature difference becomes excessive, PI
The signal of the D controller 28 is selected by the low value selector 23 and the control valve 1
Output for 1.

That is, when the moisture separation reheater inlet / outlet cycle steam temperature difference becomes excessive, a control signal for the valve closing direction of the control valve 11 is output from the PID controller 28, and this is output via the low value selector 23 to the control valve.
In addition to 11, the control valve 11 is controlled in the closing direction. In this way, the flow rate of the heating steam to the second-stage reheater 6 is controlled so that the temperature difference is within the set value.

Similarly, when the low-temperature turbine inlet steam temperature rising rate or the low-pressure turbine inlet steam temperature falling rate exceeds the respective limit values, the output signals of the PID controller 34 and the PID controller 35 are respectively low value selectors. It is selected by 22 and the high value selector 21, is output to the control valve 11, and is controlled so that the low-pressure turbine inlet steam temperature change rate becomes the limit value.

The signal from the high pressure turbine first stage rear steam chamber pressure detector 36 may be used as the input signal to the function generator 17, and the generator output may be directly detected as the input signal to the second function generator 18. The signal from the instrument 14 may be used. Furthermore, for the purpose of performing more optimal control, the slope of the function of the second function generator 18 may be changed by a signal from the high pressure turbine metal temperature detector 37 or the low pressure turbine metal temperature detector 38. Good. That is, the slope of the function may be increased as the metal temperature is higher.

〔The invention's effect〕

Since the present invention is configured as described above, even when the moisture separation reheater inlet / outlet cycle steam temperature difference or the low-pressure turbine inlet steam temperature change rate exceeds the set value at the time of a sudden load change, etc.
The amount of steam heated to the second-stage reheater is controlled, the temperature difference and the rate of change are controlled to set values, and the moisture separation reheater main body and the low-pressure turbine can be protected from life consumption due to thermal stress generation. Therefore, the reliability of the entire plant can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a moisture separation reheater control device according to the present invention, and FIG. 2 is a nuclear power generation mainly showing a moisture separation reheater to which an embodiment of the present invention is applied. Main system diagram of the plant, Fig. 3 is a main system diagram of the nuclear power plant mainly showing the conventional moisture separation reheater, and Fig. 4 is each moisture separation reheater against load by the conventional control method It is a diagram showing a steam temperature. 1 ... Reactor, 2 ... Main steam control valve, 3 ... High pressure turbine, 4
... Moisture separator, 5 ... First stage reheater, 6 ... Second stage reheater,
7 ... Low-pressure turbine, 8 ... Double water generator, 9 ... Generator, 10 ... Moisture separation reheater, 11 ... Control valve, 12 ... Moisture separation reheater control device, 13 ... High pressure turbine exhaust pressure detector, 14 ... Generator output detector, 15 ... Second stage heating steam pressure detector, 16 ... Low pressure turbine inlet steam temperature detector, 17 ... Function generator, 18 ... Function generator, 19 ... Subtractor, 20 ... PID calculation Vessel, 21 ... High price selector, 2
2 ... Low value selector, 23 ... Low value selector, 24 ... Function generator, 25
… Subtractor, 26… Subtractor, 27… Moisture separation reheater inlet / outlet cycle steam temperature difference set value, 28… PID controller, 29… Differentiator, 3
0 ... Subtractor, 31 ... Subtractor, 32 ... Low-pressure turbine inlet steam temperature increase rate limit value, 33 ... Low-pressure turbine inlet steam temperature decrease rate limit value, 34 ... PID controller, 35 ... PID controller, 36 ... High-pressure turbine Post-stage steam chamber pressure detector, 37 ... High pressure turbine metal temperature detector, 38 ... Low pressure turbine metal temperature detector.

Claims (5)

[Claims] 1. A controller for a moisture separation reheater having a two-stage reheater using main steam and high-pressure turbine bleed air as heating sources, which is provided at the inlet of the second-stage reheater. The control valve for adjusting the amount of heating steam flowing into the second-stage reheater, and the heating steam pressure of the second-stage reheater are compared and calculated with a pressure set value determined as a function of load, and the control valve And a controller for outputting a valve opening command signal to the moisture separation reheater, and a plurality of controllers for performing a comparison calculation of the steam temperature difference between the inlet and outlet cycles of the moisture separation reheater and the low temperature turbine inlet steam temperature change rate, And a selector for comparing the output signal of the controller with the valve opening command signal to select a high value or a low value and outputting a final valve opening command signal. Heater control device. 2. The control device for a moisture separation reheater according to claim 1, wherein a high pressure turbine exhaust pressure signal is used as a load signal. 3. A control device for a moisture separation reheater according to claim 1, wherein a high pressure turbine first stage after steam chamber pressure signal is used as a load signal. 4. The controller for a moisture separation reheater according to claim 1, wherein the generator output signal is used as the load signal. 5. The function of the function generator for calculating the second stage heating steam pressure set value according to the load is changed by the high pressure turbine metal temperature or the low pressure turbine metal temperature. The control device for the moisture separation reheater according to item 1.