JPS5854241B2 - Steam turbine inlet steam pressure control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steam turbine inlet steam pressure control device that controls the steam pressure to a constant level in a steam plant where the steam turbine is driven by the amount of steam from a steam source whose steam pressure fluctuates. .

Because geothermal power plants use steam emitted from underground, the steam conditions at the inlet of the steam turbine vary.

Therefore, the generator output will be affected by the steam turbine inlet steam conditions.

Small to medium fluctuations in the generator output will not affect the grid as much as the left, but if the fumarole conditions of the steam well suddenly change and the steam pressure at the steam turbine inlet suddenly increases, the power generation The machine output also increases rapidly, which has a negative impact on the grid.

One conventional measure against this problem is to adjust the main steam pressure at the inlet of the steam turbine during normal operation by remotely manually operating an electric relief valve installed in the steam reservoir, etc. (using an operating switch from the central control room). .

According to this method, if the fumarole conditions on the steam well side fluctuate rapidly and there is an abnormal pressure rise, the spring type relief valve, safety valve, or rubber valve installed in addition to the electric relief valve will be activated. Chair discs and the like can operate to protect the steam piping system as well as the steam turbine.

Another measure is to use a spring type relief valve to adjust the main steam pressure during normal operation.

Since the IJ IJ-F valve is mechanically controlled (determines the blowout pressure and blowout pressure and keeps them within a certain band), there is hysteresis and the pressure is roughly adjusted.

In any case, always detect the analog quantity (pressure), calculate it by comparing it with the rated setting pressure, and use the deviation signal to constantly control the steam relief valve and automatically finely adjust the steam pressure. There are no examples where a control device has been installed.

An object of the present invention is to provide a steam turbine inlet steam pressure control device that controls a steam relief valve so that the turbine inlet steam pressure always maintains the rated steam pressure, and prevents large fluctuations in generator output. That is.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, steam generated from one or more steam wells (steam generation sources) 1 is collected in a set of steam reservoirs 2, and is supplied to a steam turbine 5 through a main steam pipe 3 and a steam control valve 4. .

Steam turbine 5 drives generator 6 .

Although the steam control valve 4 is not shown, its opening degree is adjusted by, for example, an output signal from an automatic load control device.

By the way, a normal main steam relief valve 7 and an emergency main steam relief valve 8 are branched and connected to the main steam pipe 3, and these valves are controlled to open and close so that the steam pressure applied to the steam turbine 5 is kept within the rated value. be done.

That is, the pressure signal P1 on the inlet side of the steam control valve 4 is converted into the rated main steam pressure setting value signal P by the signal comparison section (adder) 9.
2, the opening degree of the relief valve T is controlled by the normal steam relief valve control device (hereinafter referred to as the normal valve control device) 10 via the relay contact RY1b, which will be described later, using the deviation signal P3 (-PI P2). Ru.

To explain this normal valve control device 10 in detail, 10□ is a normal main steam relief valve drive unit, which is composed of, for example, a motor and an air valve.

10□ is an automatic/manual changeover switch for the valve 7, and when the movable contact is turned to the M side, the drive section 101 can be operated manually.

Reference numeral 103 denotes a control switch for operating the drive unit 101 in an increasing direction or a decreasing direction during manual operation.

Further, 104 is a control section that supplies a control signal to the drive section 101 during automatic operation.

Reference numeral 11 denotes an emergency steam relief valve control device (hereinafter abbreviated as emergency valve control device) for controlling the valve 8, and includes a valve drive section 111 and a control section 114.

RY2a is a contact point of relay RY2, which will be described later.

A main steam pressure detector 12 operates a relay 12X when it operates.

13 is a main steam pressure rapid increase detector, which operates a relay 13X when activated.

FIG. 2 shows the above-mentioned relay RY1. This is a control circuit for RY2.

P and N are DC control power supplies, 8R. 7R-1 is a contact that is opened when the valve 8 is in the fully closed position, and 7R-1 is a contact that is closed when the valve 7 is in the fully open position.

Relay RY operates when both of these contacts 7R, , 8R are closed.

On the other hand, the relay RY2 has a contact 7R-2 that interlocks with the contact.
Output contacts 12Xa, 13 of the relays 12X, 13X
It is excited through the OR circuit of Xa.

This relay RY2 passes through contact 8R, and its a contact RY
It is designed to be self-retained by 2-al.

Next, the operation of the present invention will be explained.

In a geothermal power plant, steam is released into the atmosphere through a steam relief line before ventilating the steam turbine, but as the steam turbine is ventilated and the load on the system increases, the steam relief valve 7 is closed. Driving takes place.

Now, the steam turbine is ventilated, and the load is increased to the target load while manually closing the main steam relief valve increase/decrease switch 103 while the system is running.

After reaching the target load, the main steam relief valve manual-automatic changeover switch 102 is turned on to the automatic side A.

Thereafter, the adder 9 calculates the main steam pressure signal P1 and the rated main steam pressure setting value signal P2 to obtain the main steam pressure deviation signal P3.

The opening degree of the emergency main steam relief valve 8 is initially in the fully closed position and the limit switch 8R□ is open, so the relay RY
1 is OFF.

Therefore, the deviation signal P3 is input to the normal valve control device through the contact RY1-b, and the control section 104 creates a signal according to the polarity of the main steam pressure deviation signal P3 and the magnitude of the signal.

The normal main steam relief valve 7 is opened and closed by the drive unit 10□.

In this opening/closing operation, the main steam pressure deviation signal P3 is zero (■), that is, the main steam signal P1 is the rated main steam pressure set value signal P2.
This is done until it becomes equal to .

On the other hand, when the main steam pressure is controlled as described above, if the main steam pressure fluctuates abnormally and suddenly rises, the main steam pressure can be quickly rated using only the normal main steam relief valve 7. Since it is not possible to return to the original value, backup control using the emergency main steam relief valve 8 is performed in such a case.

Even if the normal main steam relief valve 7 is fully opened, if it cannot follow the pressure increase, the emergency main steam relief valve 8 is backed up and controlled to suddenly open.

The process will be explained below.

Abnormal fluctuations in the main steam pressure are detected by the main steam pressure signal detector 12 and the main steam pressure rapid rise detector 13.

That is, the main steam pressure signal detector 12 detects when the main steam pressure reaches a level that cannot be controlled by the normal main steam relief valve 7 alone, and turns on the auxiliary relay 12X.

Further, the main steam pressure rapid rise detector 13 detects when a large change in the main steam pressure that cannot be quickly followed by the normal main steam relief valve 7 alone occurs, and turns on the auxiliary relay 13X.

When 12X or 13X turns on, relay RY turns on, and the main steam pressure deviation signal P3 is input to the emergency main steam relief valve control unit 11, and the control unit 114 changes the polarity of this deviation signal P3 and the signal. Create a signal proportional to magnitude.

This output signal causes the emergency main steam relief valve 8 to
1□ in the opening direction.

This operation continues until the main steam pressure deviation signal P3 becomes zero M.

In addition, the control of the normal main steam relief valve 7 at this time cannot follow the rapid increase in main steam pressure, and if the valve opening at that time is other than the fully open position, the valve opening of the main steam relief valve 7 will be fully open. Relay R that operates based on the AND condition that limit switch 7R-1 is closed and main steam relief valve 8 is not fully closed.
Control is performed at the same time as the emergency main steam relief valve 8 until Y becomes ON (b contact RY, 5 in the system diagram is 0FF).

Furthermore, the emergency main steam relief valve 8 as described above is controlled not only when the main steam pressure changes abnormally, but also when the main steam pressure changes slowly so that it can be controlled by the normal main steam relief valve 7. Normal main steam relief valve 7 is rising due to change.
Relay RY is installed so that it can be controlled even when the
2, the limit switch 7R-2 is turned on to close the normal main steam relief valve 7 with it fully open.

Further, return control is performed as follows.

The emergency main steam relief valve 8 is operated only when the main steam pressure cannot be controlled by the normal main steam relief valve 7, so in this case the main steam relief valve 7 is fully open and the relay RY1 is turned ON. Therefore, the b contact RY1-b is turned OFF, and the control of the main steam relief valve 7 is stopped.

In this state, when the main steam pressure recovers to its original state, that is, when the main steam pressure decreases, the pressure is controlled only by the emergency main steam relief valve 8 (the main steam relief valve is controlled in the closing direction).
I do.

Control using only the emergency main steam relief valve 8 means that the emergency main steam relief valve 8 is in the fully closed position and the limit switch 8R-
1 is open and the normal main steam relief valve 7 is operated until the normal main steam relief valve 7 becomes below the fully open position.

In addition, if the main steam pressure drops too much and cannot be maintained at the rated value by simply tightening the emergency main steam relief valve 8, open the emergency main steam relief valve 8 fully and turn off the limit switch 8R.
Then, relay RY turns OFF and its b contact RY15
After the main steam relief valve 7 is turned ON, the pressure is controlled by the normal main steam relief valve 7.

In addition, in the above explanation, the installation location of the main steam relief non-normal use T and the main steam relief non-emergency use 8 is installed between the steam reservoir 2 and the steam control valve 4, but it is not limited to this only. Instead, it is effective in the main steam pipe system from the steam well outlet to the steam turbine inlet, such as the steam reservoir 2 main body, the steam well outlet, or any piping line along the way.

As described above, the turbine inlet steam pressure control device can control the steam relief valve so that the turbine inlet steam pressure always maintains the rated steam pressure, and can prevent large fluctuations in the generator output.

In addition, steam pipes and steam turbines can be used at lower pressures and temperatures than permissible temperatures, and their lives can be extended.

Although the present invention described above is applied to a geothermal power plant, it is not limited to this plant, but can also be used in a steam plant where steam pressure fluctuates significantly.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a steam pressure control device for a steam power plant according to the present invention, and FIG. 2 is a control circuit diagram of a relay. 1... Steam generation source, 3... Main steam pipe,
4... Steam control valve, 7... Main steam relief valve for normal use, 8... Main steam relief valve for emergency use, 9...
. . . Signal comparison section, 10 . . . Normal main steam relief valve control device, 11 . . . Emergency main steam relief valve control device, 12, 13 . . . Pressure detector.

Claims (1)

[Claims] 1. A steam generation source, a steam turbine into which the output steam from the steam generation source is input through a main steam pipe system, and a normal main steam relief valve and an emergency main steam relief valve provided in the middle of the main steam pipe system. a signal comparison unit that compares a signal corresponding to the inlet steam pressure of the steam turbine with a signal corresponding to a set steam pressure; and a pressure detector that operates when the inlet pressure of the steam turbine exceeds a predetermined set pressure. a normal main steam relief valve control device that controls the opening degree of the normal main steam relief valve according to the magnitude and polarity of the deviation of the signal comparison section when the pressure detector does not operate; An inlet steam pressure control device for a steam turbine, comprising an emergency main steam relief valve control device that controls the emergency main steam relief valve when the emergency main steam relief valve is operated.