JPH0222204B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement in a method for controlling input valve switching at the time of starting a steam turbine, and in particular, to control the control of steam control from bypass valve operation of a main steam stop valve. The present invention relates to an input valve switching control method for a steam turbine that allows switching to valve operation to be performed smoothly without fluctuations in turbine output.

(Prior Art) In steam turbine power generation equipment, an input valve is inserted in piping between a boiler and a steam turbine. As shown in Fig. 1, these input valves include a main steam stop valve 1, a small capacity bypass valve 2 that bypasses this, and
and a steam control valve 4 provided between these valves and the steam turbine 3. Since the main steam stop valve 1 does not have a flow rate adjustment function, the flow rate is adjusted by the small-capacity bypass valve 2 when the turbine is started, and after this reaches a certain opening, the main steam stop valve 1 is fully opened, and the steam control valve 4.

The details of the switching transition at the time of starting the turbine will be explained according to the flowchart of FIG. 2. First, it is confirmed whether the opening degree of the bypass valve 2 has reached the switching point by "Switching point reached? 11". At the same time, it is checked whether the turbine output of the steam turbine 3 has reached a predetermined output value by "Switching load reached? 12". If either of these steps 11 and 12 is YES, it is determined that the load increasing operation using the bypass valve is finished 13, and the bypass valve is maintained at the opening degree.

Next, the switching instruction from the operator is confirmed by "Is there a switching signal? 14", and if YES, the preconditions for switching are checked by "Is P ₁ - _{P 2} less than the specified value? 15". Ru. Here, P ₁ is the front pressure of the main steam stop valve 1 in FIG. 1, and P ₂ is the rear pressure, that is, the front pressure of the steam control valve 4.

This is because when switching from bypass valve 2 operation to steam control valve 4 operation, if the bypass valve 2 is left open and the steam control valve 4 is gradually closed from the fully open state, the steam flowing to the steam turbine 3 is throttled. As a result, the front pressure P ₂ of the steam control valve 4 increases and becomes close to the front pressure P ₁ of the main steam stop valve 1, so that when this pressure difference (P ₁ - P ₂ ) falls below the specified value This is done to stop the closing operation of the steam control valve 4, raise the bypass valve 2, and fully close the main steam stop valve 1.

That is, the front pressure P ₂ of the steam control valve 4 is increased, and this front pressure P ₂ is brought close to the front pressure P 1 of the main steam stop valve ₁ to smoothly open the main steam stop valve 1. This is for the purpose of doing so.

If step 15 is YES, "bypass valve raising operation 16" is performed, and when the main steam stop valve 1 is fully opened, "main steam stop valve 1 fully open or 17" becomes YES, the operation is completed.

On the other hand, if step 15 is NO, it is checked whether there is a load drop 18. This is to monitor whether the steam control valve 4 is closed at the time of switching, so if the turbine output decreases due to excessive throttling, the process moves to step 16 and the bypass valve 2 is closed. Do this.

In addition, if there is no decrease in the turbine output, perform the "steam control valve closing operation 19", and further perform over-throttling monitoring by checking whether the steam control valve 4 is below the specified opening 20, and if YES, the "bypass valve If the answer is NO, move on to “Pushing operation 16” and repeat “P ₁ −P ₂
The closing operation of the steam control valve 4 is performed until the value shifts to less than the specified value or 15'' and this reaches YES.

(Problem to be solved by the invention) By the way, step 15 at the time of starting the turbine mentioned above
Now, wait for the condition that P ₁ − _{P 2} is less than the specified value, and then
Moving to steps 16 and 17, the main steam stop valve 1 is fully opened. However, according to this method, in step 19, the steam control valve 4 is throttled down until the pressure _P2 becomes high to a certain extent, so if the steam control valve 4 is throttled down too much, there is a risk that the turbine output will fluctuate significantly. The load reduction check in step 18, which is used to back up this problem, has a dead band within a certain range because the turbine output is constantly fluctuating. There is a problem in that fluctuations in turbine output cannot be suppressed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an input valve for a steam turbine, which eliminates the problems of the above-mentioned conventional technology and makes it possible to reliably suppress fluctuations in turbine output at turbine startup caused by input valve switching. An object of the present invention is to provide a switching control method.

[Structure of the invention]

(Means for Solving the Problem) In order to solve the above object, the present invention provides a main steam stop valve inserted in a piping system leading from a boiler to a steam turbine, a bypass valve that bypasses the main steam stop valve, and a main steam stop valve that bypasses the main steam stop valve. When controlling the input valve consisting of the steam control valve and the steam control valve located between the steam turbine and the steam turbine, the main steam stop valve is fully closed, the steam control valve is fully open, and the bypass valve is opened to a predetermined opening. The pressure after the first stage of the steam turbine at the time when the input valve switching command is issued at
P ₀ is detected and memorized, and then the front pressure of the main steam stop valve is adjusted while the steam control valve is partially closed at a predetermined valve closing speed while the opening degree of the bypass valve is maintained at a predetermined value.
The difference P ₁ - P ₂ between P _{1 and the front pressure P 2 of} the steam control valve is detected, and if this is not below the specified value, then the first point at which the bypass valve is actually switched to the main steam stop valve is detected.
The deviation between the post-stage pressure and the above-mentioned first-stage post-pressure P ₀ is determined, and if this deviation value is not within the predetermined allowable deviation value, the bypass valve is immediately raised, the main steam stop valve is fully opened, and the steam is stopped. It is characterized by shifting to control valve operation.

(Function) According to the present invention, when switching the input valve, if the front pressure P ₁ of the main steam stop valve is too higher than the front pressure P ₂ of the steam control valve, the steam control valve is closed and the front pressure P ₂ is changed.
control so that it is high. Here, if the steam control valve is closed too much, it is inevitable that the pressure after the first stage will decrease, and the output of the steam turbine, which is proportional to this pressure, will decrease. To prevent this, the present invention monitors the pressure after the first stage. Detect and store _{the pressure after the first stage P 0 at the time when the input valve switching command is issued, compare this pressure after the first stage P 0 with} the pressure after the first stage at the time of actual switching, and calculate this deviation. If the value is within the allowable range, continue closing the steam control valve, and if the value is outside the allowable range, the first
If the pressure drops after the stage, immediately operate the bypass valve and fully open the main steam stop valve.

Therefore, since the pressure after the first stage is monitored, the steam control valve will not be closed too much, the pressure will not become too low after the first stage, and the steam pressure will be proportional to this pressure. There is no fluctuation in the output of the turbine. Note that the above-mentioned allowable range is set within the range of fluctuations in the pressure after the first stage that can normally occur when switching the input valve.

(Example) The details of the present invention will be explained below with reference to FIGS. 1 and 3.

In the input valve switching device shown in FIG. 1, when the present invention is applied, the front pressure P ₁ of the main steam stop valve 1 and the small capacity bypass valve 2 that bypasses it, and the front pressure P ₂ of the steam control valve 4 Besides, the pressure P ₀ after the first stage of the steam turbine 3 is detected and stored.

In Fig. 3, first, "Switching point arrived? 11"
to check whether the opening degree of the bypass valve 2 has reached the switching point, and in parallel check whether the switching load has been reached or not.
2" to confirm whether the turbine output of the steam turbine 3 has reached a predetermined output value. If either of these steps 11 and 12 is YES, the "Load increase by bypass valve completed 13" is confirmed. After performing the operation, the switching instruction from the operator is confirmed by checking "Switching instruction present? 14".

Up to this step, it is the same as the conventional method, but
In the present invention, when step 14 is YES, the pressure P 0 after the first stage of the steam turbine 3 is detected and stored in the "storage ₂₁ of the pressure P ₀ after the first stage". This pressure P ₀ is proportional to the output of the steam turbine 3, and by detecting this value, the energy given to the steam turbine 3 can be monitored.

When this pressure P ₀ memorization operation is completed, the pressure drop due to the bypass valve 2 is checked again by "Is P ₁ - _{P 2} less than the specified value or 15" as in the past,
If YES, the process moves to the bypass valve raising operation 16 to fully open the main steam stop valve 1, and when the ``main steam stop valve fully open 17'' becomes YES, the process is completed.

On the other hand, if step 15 is NO, check ``Is the pressure after the first stage within the allowable deviation value of _P0 ?''. In this step 22, first, the pressure after the first stage at the time of checking is actually measured, the deviation value between this actually measured pressure and the pressure P ₀ stored in step 21 is determined, and this deviation value is determined to be acceptable. Check whether it is within the specified deviation value.

If this step 22 is YES, it means that the pressure after the first stage at the time of checking is approximately equal to the pressure P ₀ stored in step 21. If there is no decrease in the turbine output at this time, step 18 is executed. After that, "steam control valve operation 19" is performed. When the steam control valve 4 starts to close, the pressure in front of the steam control valve 4 increases.
P ₂ is high, and inevitably after the first stage the pressure goes low. If the pressure after the first stage becomes too low, it means that the steam control valve 4 is throttled too much, and if it is throttled too much, the output of the turbine 3 will decrease, which is not preferable.

Next, "Is the opening degree of the steam regulating valve less than the specified opening? 20" is checked, and if this step 20 is NO, that is, if it is not throttled too much, step 20 → 15 is checked.
→22, and in this step 22, it is checked again whether the deviation value of the pressure after the first stage at that time is within the allowable deviation value.

Then, step 15 → 22 → 18 → 19 → 20 →
15 is repeated, and in the process, ``Is the opening of the steam control valve less than the specified opening? 20'' is YES, ``Is there a decrease in turbine output? 18'' is YES, or ``The pressure after the first stage is
When it is determined that either P ₀ is within the allowable deviation value or 22 is NO, the bypass valve lifting operation 1 is immediately performed.
6” is performed.

Therefore, according to this embodiment, steps 21 and 22, which are different from the conventional ones, are provided to monitor excessive throttling of the steam control valve 4 during the input valve switching operation, so that the pressure after the first stage is set within an allowable range. If a drop exceeding 1 is observed, the bypass valve raising operation 16 is immediately performed, the main steam stop valve is fully opened 17, and thereafter the steam amount is controlled by the steam control valve 4. Therefore, the drop in the pressure after the first stage exceeding the allowable range during the input valve switching operation is suppressed, and as a result, the fluctuation in the output of the turbine 3, which is proportional to the pressure after the first stage, is ensured. It can be suppressed.

Incidentally, when the input valve is switched, the pressure after the first stage naturally fluctuates compared to the pressure P ₀ at step 21. However, according to this embodiment,
The allowable range in step 22 is set as the range of such small pressure fluctuations that normally occur. If the pressure drops too much after the first stage beyond this range, immediately operate the bypass valve (16).
will be carried out.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the pressure P ₀ after the first stage of the steam turbine at the time when the input valve switching command is issued is detected and stored, and the bypass valve operation is switched to the steam control valve operation. Since the valve is switched in such a way that the pressure after the first stage at the time of actual switching is kept within its allowable deviation value, it is possible to suppress fluctuations in the turbine output and perform the switching smoothly.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a turbine input valve in a steam turbine power generation facility, FIG. 2 is a flowchart showing a conventional input valve switching method, and FIG. 3 is a flowchart showing an embodiment of the method of the present invention. 1...Main steam stop valve, 2...Bypass valve, 3...Steam turbine, 4...Steam control valve, _P1 ...Pressure before main steam stop valve, _P2 ...Pressure before steam control valve, _P0 ...Input valve switching command Steam turbine first stage pressure at the time of exit.

Claims (1)

[Claims] 1 Switching control of input valves consisting of a main steam stop valve inserted in the piping system leading from the boiler to the steam turbine, a bypass valve that bypasses this valve, and a steam control valve placed between these valves and the steam turbine. At this time, the pressure P after the first stage of the steam turbine at the time when the input valve switching command is issued with the main steam stop valve fully closed, the steam control valve fully open, and the bypass valve opened to a predetermined opening degree. ₀ is detected and memorized, and then the main steam stop valve's front pressure P ₁ and the main steam stop valve are The difference (P ₁ - P ₂ ) between the steam control valve and the front pressure P ₂ is detected, and if this is not below the specified value, then after the first step when the bypass valve is actually switched to the main steam stop valve. The deviation between the pressure and the pressure after the first stage P ₀ is determined, and if this deviation value is not within the predetermined allowable deviation value, the bypass valve is immediately raised, the main steam stop valve is fully opened, and the steam control valve is closed. A method for controlling input valve switching of a steam turbine, characterized by shifting to operation.