JPS6011605A - Steam turbine control - Google Patents

Abstract

PURPOSE:To curb abrupt uprise of a turbine rotation, by providing two normally closed valves which are arranged in series in steaming systems leading to the steam turbine, in order to let the second valve start turbine control, as well as the first valve is fully opened, when the second valve becomes ready to operate. CONSTITUTION:Initial opening of a motor driven valve 1 is established through function generators 12-14, based on each output signal from a main steam pressure detector 10 and feed-water hydrometer 11 when the cooling system of a nuclear reactor in an atomic power station of boiling water model starts at a time of atomic segregation. Rotational frequency of a steam turbine 4 is controlled by letting a governing valve 3 start closing from its full opening when the steam turbine 4 is started and rotational frequency is raised up to specified level. On the other hand, a motor driven valve 1 is fully opened as per the output of full opening signal generator 15, after exciting a relay 19 via logic circuit 16 according to a control oil pressure establishment signal 23a, rotational frequency signal 21a denoting that turbine frequency goes beyond the specified level and an opening signal 22a indicating start of closing of governing valve 3.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a steam turbine control method, and in particular to a reactor isolation cooling system (hereinafter referred to as RaIc) that constitutes a reactor auxiliary system in a boiling water nuclear power plant. The present invention relates to a steam turbine control method suitable for controlling the start-up of a pump-driving steam turbine used in a pump-driving steam turbine system.

[Technical background of the invention]

The RaIc system in a boiling water nuclear power plant belongs to the reactor auxiliary system, which is auxiliary equipment for the reactor, along with fuel handling equipment, fuel pool cooling purification system, reactor coolant purification system, residual heat removal system, etc. This RaIc system uses some of the steam in the reactor to drive the steam turbine in order to maintain the water level in the reactor if the water supply system to the reactor stops for some reason after the reactor is shut down. This equipment injects steam condensed water from the residual heat removal system or condensate storage tank water, etc. into the reactor core using a water supply pump directly connected to the reactor core. For this reason, the reliability required of such equipment is extremely high.

FIG. 1 shows a schematic systematic diagram of the well-known RaIc system. As is clear from the figure, the ReIC system consists of a pump-driving steam turbine +
In addition to the main system equipment consisting of.

a steam pipe line g connecting the nuclear reactor 7 and the steam turbine;
It is composed of many valves such as the electric valve installed in the steam pipe line g, the main steam stop valve, the speed regulating valve 3, the main piping such as the water supply pipe that connects these, and the main steam isolation valve 9. is common.

In this configuration, when the main steam isolation valve 9 is closed during a scram of the nuclear reactor 7, the reactor system becomes isolated from the steam turbine system (not shown), and the reactor water supply system is stopped. As a result, the pressure inside the reactor rises, causing a safety relief valve (not shown) to operate. On the other hand, due to the loss of water supply, the reactor's decay heat continues to generate steam, so the reactor water level continues to fall. In this state, when the water level in the reactor falls and reaches a certain specified value, an automatic start signal for the RO system 0 is generated, and the electric valve l provided in the steam pipe line It/C of the steam turbine is fully opened.

On the other hand, the main steam stop valve J and the speed governor J are mechanically fully opened in advance before starting the steam turbine t.
The steam that has passed through the main steam stop valve.

It flows into the steam turbine 1 through the governor valve 3 and starts the steam turbine.

By the way, when starting a typical steam turbine,
First, the turbine is rotated by changing the governor valve 3 from a fully closed state to an open state, whereas in the case of an RCIC steam turbine, the governor valve 3 is fully opened before starting, as mentioned earlier. However, this type of steam tarping is only for emergency use.

This is because the steam turbine 1 must be started even under conditions where the control oil pressure, which is the power source for controlling the steam turbine 1 and the driving source for the governor valve 3, is not established. In other words, the electric valve l driven by the DC power supplied from a Nonozuteri etc. is first opened, the steam tarping is started, and the control power obtained by the rotation of the steam turbine l and a pump (not shown) directly connected to the steam turbine are used. This is to allow normal operation by the regulating valve 3 to begin after the hydraulic pressure to be generated is established. In this way, after starting the steam turbine q, as its rotation increases, cooling water is sent to the reactor from the RO work C pump 5 directly connected to it, cooling the core of the reactor 7 and Recovering the reactor water level becomes possible.

FIG. 2 shows an electrically operated valve 1 when a steam turbine is manually started using a conventional steam turbine control method.

The opening degree of each of the regulating valves 3/A, ? A and the rotation speed of steam tarping! It is a characteristic diagram showing the relationship of IA.

As shown in Figure 1, when an automatic start signal for the RO system 0 system is generated at time T1, a fully open signal is first input to the electric valve l, and the electric valve opening /A changes from the fully closed state to the fully open state. The opening degree changes over a certain period of time toward 10. The steam from the electric valve is fully open to the main steam stop valve and the regulating valve 3.
into the steam turbine l. The steam tarping starts to rotate for the first time after a certain time delay ΔTI from time T1, but in this case, a large amount of steam passes through the electric valve l and directly flows into the steam turbine l, so the increase in the rotational speed gA is very large. It becomes sudden. by the way.

It is desirable that the rotational speed lIA of the steam tarping is stabilized when it reaches the rotational speed determined by the required value of the discharge amount from the RO pump. However, in reality, the regulating valve, 3
The valve opening degree of 3A is fully open at 3 degrees before startup, and there is a delay in the hydraulic pressure that is the drive source for the governor valve 3, which is secured as the steam turbine rotation speed +A increases. For a reason.

The turbine rotational speed IIA cannot be immediately stabilized, and exceeds the target rotational speed, resulting in an irregular seat. This automatic seat can then be stopped by rapidly closing the regulating valve 3, which is driven by the established oil pressure, to nearly fully closed.

On the other hand, steam tarping will start to reduce the rotational speed.

As a result, the rotational speed lIA of the steam turning becomes lower than the target rotational speed and undershoots, and due to the action of the regulating valve 3, the rotational speed lIA starts to rise again. In this way, after repeating automatic shoot and undershoot several times, it becomes possible to control the speed of the steam turbine to a rotational speed commensurate with the required discharge amount of the RO work C pump 3.

[Problems with background technology]

However, the behavior of the rotational speed lIA of the steam turbine l at the time of startup includes the following problems. First, when the rise of the oil pressure, which is the drive source for the regulating valve 3, is slow, the peak value of the rotational speed of 7 A caused by the automatic chute is caused by an over-speed prevention emergency (not shown) installed as a steam tarping protection device. This could cause the governor to operate, potentially causing the turbine to trip. First, the rapid increase in the rotational speed of the steam turbine exerts a large impact force on not only the main body of the steam turbine, but also the turbine bearings, gears, etc., which has a serious impact on its lifespan and reliability. It's about giving.

Thirdly, after the steam tarping is started, the rotational speed is unstable until it reaches the regulating point, which causes vibrations and induces malfunctions of other equipment such as monitoring devices and protection devices. It is a possibility.

As mentioned above, although the reliability required for the RCIC system is extremely high, conventional turbine control methods have problems with reliability, especially during startup. Some kind of countermeasures were needed.

[Purpose of the invention]

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to determine the opening degree of the electric valve provided at the inlet of the steam turbine based on the main steam pressure and the required amount of water supply at the time of startup of the steam turbine used in the RCIC system. Open it to the desired opening,
Temporarily restricts the amount of steam flowing into the steam turbine, suppresses the sudden increase in the rotational speed of the turbine and the accompanying shocks and vibrations, making it possible to realize a highly reliable ROIC system. The present invention provides a method for controlling a steam turbine.

[Summary of the invention]

In order to achieve the above object, the present invention computationally controls a normally closed first valve provided in a steam system leading to a steam turbine to the degree of opening required to bring the steam turbine to the required rotational speed. It detects that the normally closed 7th valve connected in series with the 1st valve to control the rotation speed is ready for operation, and then fully opens the 7th valve and A steam turbine control method is provided in which a steam turbine is controlled by a valve.

[Embodiments of the invention]

The present invention will be described in detail below with reference to two drawings.

FIG. 3 is a block diagram showing the basic concept of a steam turbine control method according to an embodiment of the present invention. In the figure, the main steam pressure detector lθ detects the main steam pressure of the steam pipe line t and outputs a detection signal P□. The water supply flow rate setter ti generates a flow rate setting signal QR. The function generator 12 performs a function calculation on the flow rate vs. rotation speed characteristic (hereinafter referred to as Q-H characteristic) of the RC pump S based on the signal obtained by adding the correction signal ΔP to the pressure detection signal P1 and the flow rate setting signal QRK, and calculates the rotation speed. Generates signal N□. The function generator 73 performs a function calculation on the turbine rotation speed versus required steam amount characteristic (hereinafter referred to as NG characteristic) based on the earth pressure detection signal P and the rotation speed signal N1 to generate a steam amount signal G□. The function generator /lI performs a function calculation on the electric valve flow rate versus opening characteristic (hereinafter referred to as G-IJ characteristic) based on the pressure detection signal P and the steam amount signal G1 to generate a valve opening signal L□. A full open signal generator/generates a full open signal for the electric valve l. Logic circuit/6 is the steam tarping rotation speed signal 211! A signal is generated based on the logical sum condition of L, the opening degree signal of the governor valve 3, λ4, and the control oil accuracy (9), and the truck signal na, and the relay 19 is operated. Addition circuit/Full open signal generator/3 given via valve opening signal L□ and contact of relay 19
The full open signal from the valve is added and sent to the valve opening controller/g. The valve opening adjuster 7g adjusts the opening of the electric valve. Note that the startup circuit generates a startup signal for the RO system 0 system.

Incidentally, the function generator 1 is given the feed water flow rate set by the feed water flow rate setting device // as the flow rate setting signal Q3, while the feed water flow rate of the reactor 7 corresponding to the pressure detection signal P□ from the main steam pressure detector IO is When the internal pressure is given, the required pump rotation speed is output as the rotation speed signal N1 based on the system hella r curve and the pump rotation speed characteristic 2, that is, the QH characteristic of the RO pump 3.

Note that the N-G characteristics set in the function generator 13 are as follows.

The rotation speed of the steam tarping given by the rotation speed signal N□ is related to the turbine shaft power "KW", and further the shaft power K
(to) is determined based on the relationship that W is determined by the amount of steam flowing into the steam turbine. However, if the steam conditions at the inlet of the steam tarping differ, the amount of steam flowing into the steam tarping will also differ when obtaining coaxial power.Therefore, in general, the higher the steam pressure, the smaller the amount of steam flowing into the steam tarping tends to be. . By the way, RaI
The steam in the steam pipe line g of system a is in a state close to saturated steam, and once the pressure is reduced, the energy held by the steam is uniquely determined.

Furthermore, the G-L characteristic of the electric valve set in the function generator 11 is such that if the steam condition on the valve inlet side, specifically the main steam pressure, is determined, the amount of steam passing through the valve and the valve lift will be It is established based on the fact that there is a certain relationship.

In this configuration, when a startup signal is input from the startup circuit J to the ROIO system due to scram etc. of the reactor 7, the main steam pressure detector 10 first detects the main steam pressure and outputs the pressure detection signal P□. Send to function generator /2°/3, /4'. The function generator/co which is given the pressure detection signal P□ inputs the signal obtained by adding the correction signal ΔP to this pressure detection signal P□ and the flow rate setting signal QR from the water supply flow rate setting device//,
To the RC engineering C pump k ・Set the required number of revolutions to the number of revolutions signal N□
Output as .

Incidentally, the reason for adding the correction signal ΔP is that the discharge pressure of the RO work 0 bonzo left must be set to the pressure in the reactor plus the piping loss between the pump discharge port and the reactor. In addition,
The correction signal ΔP is generated based on the flow rate signal QR from the water supply flow rate setting device //, since the piping loss is affected by the flow rate. This rotational speed signal N is inputted together with the pressure detection signal P to the function generator 13, where the required amount of steam for steam tarping is calculated and output as the amount of steam signal G□. This steam amount signal G1 is sent to the function generator/Q, which calculates the required valve opening by inputting the steam amount signal G□ and pressure detection signal P□ of the function generator Output as L□.

The valve opening signal L□ obtained here is Rf:! under the detected main steam pressure. This is a signal requesting the valve opening degree of the electric valve that can flow the amount of incoming steam from the steam tarping necessary to obtain the required rotational speed of the IC pump 5. This valve opening signal L1 is applied to the valve opening regulator /g via an adder /7, and as a result, the motor-operated valve 1 is opened by the valve opening regulator /g to the required valve opening. Steam turbine q due to opening operation of electric valve /
The rotational speed increases, and at the same time, the RO pump 3 also starts supplying water to the reactor.

On the other hand, as the rotational speed of the steam turbine increases, the control hydraulic pump (not shown), which is the drive source for the governor valve 3 directly connected to the steam turbine 1, begins to perform its original function, controlling the steam flow rate to the steam tarping. It becomes possible to shift from the striped electric valve 1 to the speed regulating valve 3.

At this point, there is no longer a need to maintain the electric valve / at the initial valve opening degree, and it becomes necessary to fully open the electric valve l.

In this case, the conditions under which it can be confirmed that the turbine control system is equipped with the original function are required: the rotational speed signal 2/a indicating that the steam turbine rotational speed has reached a certain rotational speed, and the actual opening change of the governor valve 3. By detecting the opening signal U2a indicating that the control hydraulic pressure has exceeded a certain value, the control oil pressure establishment signal Ua indicating that the control oil pressure has reached a predetermined value, etc. through the logic circuit/6, and operating the relay 79. A full open signal from the full open signal generator/left is sent to the valve opening regulator/g via an adder/7, and the electric valve/ is brought into a fully open state.

Next, the steam turbine rotation speed IA at the time of startup of the RoIO system when the steam turbine control method of this embodiment is applied
, the opening degree/A of the electric valve I, and the opening degree 3A of the regulating valve 3, and their relationship will be explained with reference to the characteristic diagram shown in FIG. By the way, in order to clarify the differences from the characteristic diagram in Fig. 2, in Fig. &,? A is indicated by a broken line.

Now, when the activation signal to the ROIC system is inputted at time TI, the initial opening degree of the electric valve / is set by the calculation system based on the configuration shown in FIG. 3, and is sent out as the opening degree signal L□. As a result, the electric valve / is the opening degree /.

It opens from the state to the state of opening degree l. Steam is supplied to the steam tarping by the movement of the electric valve l in the opening direction, so
The turbine rotation speed A will increase after a certain time delay, but the rate of increase in the rotation speed at this time is limited by the amount of steam flowing into the tarping A by the opening degree of the electric valve /. This will be slower than before. As the rotation speed QA of the steam tarping increases, the control oil pressure, which is the drive source for the governor valve 3, is gradually established by the control oil pressure pump, and at time T2, this reaches a certain rotation speed lIa' of the steam turbine q. If this is established, the governor valve 3 will begin to close from the full opening degree of 3 degrees, and will be responsible for controlling the rotational speed of the steam turbine 1. On the other hand, the electric valve / is the control oil pressure establishment signal 3a
, a rotational speed signal 2/a indicating that the turbine rotational speed has reached a certain level or higher, an opening signal indicating that the regulating valve 3 has begun to close, etc. are detected by the logic circuit/6. The opening degree is controlled based on the conditions from the opening degree /, to the fully open degree l. and becomes fully open at time T3. On the other hand, the turbine rotation speed +A is the electric valve opening from 1 to fully open.

Even if the rotation speed starts to shift, the rotation speed control is transferred to the regulating valve 3, so even if some overshoot occurs, the rotation speed will not increase suddenly and will almost reach the required target rotation speed. It is controlled stably and enters a substantially stable control state at 1 time T4.

Note that one of the conditions required for the RCIC system is that the time from the time T1 when the turbine start signal is input until the rated water supply flow rate is reached must be within a certain specified time. For example, even though the rotation speed increases relatively slowly at startup, the time required for stabilization can be kept short because the automatic shoot and undershoot are small, and the time T4 is almost the same as in the conventional case. In this case, it is possible to achieve the target flow rate.

By the way, although the above embodiment illustrates the case where an electric valve is used to start the steam turbine, it goes without saying that a similar control method can be applied to other electric-pneumatic regulating valves, etc. .

〔Effect of the invention〕

As described above (1) According to the present invention, when starting a steam turbine for driving a pump used in an RC! It prevents damage, prevents malfunction of the emergency governor due to an increase in the number of rotations, and malfunction of monitoring instruments and detectors due to vibration caused by unstable control, and further secures the required amount of water supply quickly within the specified time. I made it possible.Also RC
This makes it possible to improve the reliability of the engineering C system and obtain a steam turbine control method that is effective in the operation of nuclear power plants.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a well-known reactor isolation cooling system. Figure 1 shows the turbine rotation speed and electric valve opening when starting the ReIC system using the conventional steam turbine control method. A characteristic diagram showing the behavior of the governor valve opening. FIG. 3 is a block diagram showing the basic concept of a steam turbine control method according to an embodiment of the present invention. FIG. 4 is a characteristic diagram showing the behavior of the turbine rotational speed, the electric valve opening degree, and the regulating valve opening degree at the time of starting the ReIC system according to the configuration shown in FIG. l...Electric valve, 3...Governing valve, t...Steam turbine. Left...RO engineer C? pump, 7... nuclear reactor, //...
Water supply flow rate setting device, /ko, /3, /4'...Function generator. Applicant's representative Inomata Kiyo-ku is pregnant.

Claims (1)

[Claims] A normally closed first valve provided in the steam system leading to the steam turbine is computationally controlled to the opening degree necessary to bring the steam turbine to the required rotation speed, and the first valve is operated to control the rotation speed of the steam turbine. It is characterized by detecting that the second normally open valve connected in series is ready for operation, then fully opening the first valve and causing the first valve to control the steam turbine. A steam turbine control method.