JPS62323B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Application) The present invention relates to a speed governor device for a dual system steam turbine control device used in a nuclear power plant or a thermal power plant. In a steam turbine governor device that uses a dynamic switching method to control the opening of each turbine steam valve, by simply adding simple devices and functions, the output control signal of a pair of governors can be changed to The present invention relates to a speed governor device for a steam turbine that can accurately determine which speed governor is abnormal when a difference greater than a predetermined value occurs. (Prior Art) First, as a conventional example, the schematic structure of an electro-hydraulic speed governor applied to a single-stage reheat steam turbine used in a thermal power plant is shown in Fig. 1 along with the connection with the turbine steam system. Shown in block diagram. The contents of FIG. 1 will be explained by dividing them into two groups: those related to the steam generator, turbine and steam system, and those related to the electro-hydraulic speed governor. The steam generated by the steam generator S.GEN is passed through steam stop valves SV1, SV2 and steam control valves CV1 to CV.
4 to the high pressure turbine HP. The enthalpy of the steam that has done work in the high-pressure turbine HP has decreased. Therefore, in order to increase the efficiency of the power generation plant, this steam is transferred to the steam generator S.
It is heated again using the reheater REHEAT in GEN. The enthalpy-enhanced steam in the reheater REHEAT is supplied to the medium and low pressure turbines IP/LP via reheat steam stop valves RSV1, RSV2 and intermediate check valves ICV1 to ICV4. The steam that has done work in the low-pressure turbine LP is sent to the condenser COND and condensed, and this water is returned to the steam generator S.GEN. In a typical example, there are two steam stop valves (SV1 and SV2) and four steam control valves, as shown in the figure.
(CV1 to CV4), two reheat steam stop valves (RSV1 and RSV2), and four intermediate check valves (ICV1 to ICV4). In addition, under normal operating conditions, excluding when the turbine speeds up or when an emergency stop occurs, the steam stop valve SV1,
SV2, intermediate check valve ICV1 to ICV4, reheat steam stop
RSV1 and RSV2 are fully open, and steam generator S.
The steam flow rate supplied from GEN to the turbines HP, IP/LP is adjusted only by steam control valves CV1 to CV4. In this case, as a method for controlling the opening and closing of each steam control valve CV1 to CV4 for regulating the steam flow rate, for example,
There is a way to open them in the order of CV1 → CV2 → CV3 → CV4. In addition, other steam valve opening/closing control methods have been reported that reduce stress on the turbine rotor. Next, the basic functions related to the electro-hydraulic speed governor will be explained. This speed governor controls the opening and closing of each of the ten turbine steam valves mentioned above, and constitutes the troublesome part. The basic functions for turbine speed and load control are as follows. The turbine rotational speed signal 1 is obtained, for example, by an actual rotational speed detector SD that detects the number of rotational teeth of a gear attached to a turbine shaft. Then, the rotation speed signal 1 and the turbine target rotation speed signal 2
The deviation from the above is calculated by the computing unit AD1. This deviation is (when the speed adjustment rate is δ),
It is multiplied by 1/δ and added to the load setting signal 4 from the target load setting device LD.REF in an adder AD2. Note that LMT is a rate of change controller. When the actual turbine rotation speed signal 1 is equal to the turbine target rotation speed signal (S REF),
As is clear from the above explanation, load setting signal 4
This means that only this is added to the subsequent control circuit. Note that the load setting signal 4 is generally a target load setting device having an integral characteristic of 1/SA as shown in FIG.
Given by LD.REF and rate of change controller LMT. Furthermore, this target load setting device LD.REF can receive load increase/decrease commands “L” from other devices or the driver.
It is configured to accept "R". The output signal 5 of the adder AD2 mentioned above is applied to the next stage low value priority circuit LVG. In the example of FIG. 1, the output signal 6 of the load limiter LLM and the output signal 7 of the pressure limiter PM are applied together with the aforementioned signal 5 to the low value priority circuit LVG, and each of the aforementioned signals 5, 6, 7 is applied to the low value priority circuit LVG. Among them, the smallest signal is
The output signal of the low value priority circuit LVG is the turbine integrated valve opening command 8, which controls the openings of various steam valves. Note that PD in FIG. 1 is a main steam pressure detector, and its output is applied to the calculator AD3 together with the reference pressure signal PR. The output of the calculator AD3, that is, the deviation of the main steam pressure from the reference value, is supplied to the pressure limiter PM. As is well known, when the turbine speed drops due to a sudden increase in the load in the power system, the load limiter LLM suddenly opens the steam valve in response to the above signal 5, causing undue stress on the turbine. This is to prevent additional burden. In general, the speed deviation signal 3 is set to have a slightly larger value than the signal 5 when the speed deviation signal 3 is zero. As is well known, the role of the pressure limiter PM is to reduce the pressure of steam given to the turbine from the steam generator S.GEN due to a failure of the steam generator S.GEN or its control device. In the event that
The purpose is to control the turbine steam control valves CV1 to CV4 in the closing direction to support recovery of steam pressure. Next, the function generators FGC1, FGC2, and
FGI1... receives the turbine integrated valve opening command signal 8, and operates steam control valves CV1 to CV4, respectively.
Intermediate blocking ICV1 to ICV4, steam stop valve SV1 to SV
2, etc., to control the opening degree. For example, if the turbine operation method is such that four steam control valves CV1 to CV4 are sequentially opened to increase the steam flow rate, for a small value of the turbine joint valve opening command signal 8, The output of FGC1, which should control the control valve CV1 that should be opened first, is large, but it controls the control valve CV4 that should be opened last.
The output of FGC4 is zero. Here, the opening degree control of each steam valve based on the output of each function generator FGC1, FGC2, etc. will be explained. Since each steam valve has a nonlinear relationship between its opening degree and the flow rate of passing steam, each of the function generators provides an inverse function characteristic to the steam valve cylinder opening detection feedback signal system, which will be described later. It works like this. In addition, each function generator FGC1, FGC2, FGI1
The mechanism (encircled by the two-dot chain line in Fig. 1) and method for controlling the opening degree of the corresponding steam valve according to the outputs of ... etc. are the same for all function generators. In the following, only the part related to the function generator FGC1 will be explained. The electric-hydraulic signal converter SERV converts the electric signal output 11 of the amplifier K1 into a control oil amount signal 13,
The amount of hydraulic oil corresponding to the signal 13 is applied to the cylinder.
Send to CYRN. This causes the piston inside the cylinder CYRN to
A stroke (displacement) proportional to the amount of the hydraulic fluid is generated. The stroke (displacement) is the mechanical lever
It is transmitted to the steam control valve CV1 via LV, and its opening degree is controlled. The stroke of the piston in the cylinder CYRN is detected by its detector DIFT, and the detection signal is supplied as a feedback signal 10 to the calculator AD4 via the converter POS. On the other hand, the valve opening degree target signal 9, which is the output of the function generator FGC1, is also applied to the calculator AD4. Output of computing unit AD4 - that is, steam control valve CV
A deviation signal with respect to a valve opening target signal 9 of an actual opening of 1 (represented by a signal 10) is amplified by an amplifier K1 and then supplied to an electro-hydraulic signal converter SERV. That is, the actual opening of the steam control valve CV1 is controlled to always match the valve opening target signal 9 by the component surrounded by the two-dot chain line in FIG. As explained above, arithmetic unit AD4 → electricity
Hydraulic signal converter SERV → Cylinder CYRN → Detector
The reason for the provision of a minor control loop consisting of DIFT → converter POS → computing unit AD4 is that from the valve opening target signal 9, changes in the opening of each steam valve → changes in the amount of steam in the turbine rotor → changes in the turbine rotation speed →Speed deviation→Function generator FGC1 A minor loop like this is provided in the major loop with a large time delay to quickly respond to the steam valve opening control and stabilize the valve opening. . Now, in many cases, the control function part for realizing such a complicated control operation is composed of an electric circuit. The following two methods are used to do this:
is known. (1) Analog control method A desired function is realized by mounting semiconductor integrated circuit elements on a printed board and wiring between them. (2) Digital control method The various required functions are stored in the memory of a digital computer and calculated by the central processing unit (CPU), and the obtained control commands are sent via the process input/output circuit (PI/O). What supplies the turbine steam valve (specifically, an electro-hydraulic converter using high-pressure oil). When digital control type hardware is adopted, there is an advantage that some kind of redundancy system can be easily applied in order to improve the reliability of the electro-hydraulic governor system. In other words, it can be said that the digital control method is superior to the analog control method from the viewpoint of ease of realizing a highly reliable system. Redundancy methods can be broadly divided into static redundancy methods.
Redundancy), dynamic redundancy
There are three types of matings: redundancy, and hybrid redundancy. For each series, various methods have been considered that are suitable for requirements such as reliability requirements, ease of repair in the event of a failure in a single system, equipment installation dimensions, and cost. FIG. 2 shows an example of the configuration of a conventional one-standby dynamic switching electro-hydraulic transmission system. In the figure, the electro-hydraulic governors A and B are, for example, the first
Each has the functions shown in the figure independently, and the output of each is supplied to various turbine steam valve drive electro-hydraulic converters through several changeover switches SW. With the switch SW connected to side A,
When speed governor A is out of order, if speed governor B is not out of order, the switch SW is switched to the speed governor B side. As a result, the standby speed governor B takes over the control of the turbine, allowing the turbine to operate. On the other hand, governor A excluded from control can be repaired during turbine operation. The configuration of the switching logic of the switch SW is such that the speed governor that is participating in the control diagnoses itself in terms of hardware and software, and when it recognizes itself as having failed, it relinquishes control and switches to the standby side. This transfers control to the speed governor. However, the above conventional method has the following problems. In other words, if an abnormality occurs in the speed governor that is in charge of control, it is not possible to detect the abnormality with 100% accuracy. In other words, even in digital computers, “Who checks the checker” in the above system
This means that the problem remains. In addition, in the above conventional system, if governors A and B
Even if a separate circuit is provided to distinguish between the outputs of A and
Another problem is that it is not possible to determine which one is correct. One way to solve the above problem is to use a speed governor (controller) with the same function as speed governors A and B.
By installing a new C and using majority logic for each output,
The problem is to find a faulty speed governor and adopt a configuration method that does not apply it to control. However, this method has drawbacks such as increased cost and installation area due to the provision of a new speed governor C as a controller. (Purpose) The present invention provides a speed governor device for a steam turbine of a standby dynamic switching type, in which when a difference occurs between the outputs of the speed governor under control and the speed governor on standby, It is an object of the present invention to provide a speed governor device for a steam turbine equipped with a simple discrimination circuit for determining whether the speed governor is correct and making it possible to reliably perform a speed governor switching operation. (Summary) In order to achieve the above object, the present invention provides a monitoring circuit C that performs simple calculations unrelated to the speed governor function, and adds the same calculation function to each speed governor A and B. However, when a difference occurs between the outputs of two speed governors A and B with the same function that constitute the 1-standby dynamic switching system, an adjustment is made for each speed governor A and B and the monitoring circuit C. A simple calculation unrelated to the speed function (for example, calculating the acceleration rate of the turbine speed) is newly executed, and the switch is connected to the governor A or B side that matches the majority logic of the calculation results of these three parties. It is composed of (Example) An example of the present invention will be described in detail below with reference to FIGS. 3 and 4. In these figures, the same reference numerals as in FIG. 1 represent the same or equivalent parts. In FIG. 3, governor B has the same configuration as governor A, so parts not directly related to the following explanation are omitted from illustration. The joint valve opening command signal 8 of the turbine control valve, which is the most important intermediate variable in controlling the various steam valves of the turbine, is taken out from each of the governors A and B and added to the calculator AD5. Compare. Add the obtained difference signal 15 to the comparator COMP,
For example, when a difference of about 2% of the full scale occurs, a logic output of "1" is output (in the figure,
(indicated by activation signal ABd). It is clear that other valve opening command signals or the like may be used instead of the signal 8. When the comparator COMP generates the logic output "1" (starting signal ABd) as described above, the turbine acceleration rate calculator ACS provided in each governor A, Introducing the acceleration command signal 8 or using this turbine acceleration rate calculator
The ACS is activated to calculate the acceleration rate of the turbine based on the change in the command signal 8. The results of the calculation are supplied to the acceleration discriminator ARD and the deceleration discriminator ALD for each of the speed governors A and B. Acceleration discriminator ARD and deceleration discriminator
In ALD, when the calculation result exceeds a predetermined acceleration/deceleration rate (for example, 0.1% per second), a deceleration signal AL or an acceleration signal AR is output. In addition, as is clear, each of the above-mentioned speed governors A and B
The acceleration/deceleration rate in may be always executed not only when the activation signal ABd is generated from the comparator COMP, but also when the logic output is not generated. Next, referring to FIG. 4, the operation of the monitoring circuit C when the activation signal ABd is generated from the comparator COMP as described above will be explained. FIG. 4 is a block diagram of the monitoring circuit C. The activation signal ABd is supplied to AND gates AND1 and AND2, and is also applied to a turbine acceleration rate calculator ACS. The turbine acceleration rate calculator ACS includes a rotation speed detector SD (Fig. 1).
An acceleration rate calculation is performed based on the actual rotational speed signal 1 of the turbine measured at . The calculation results are supplied to the acceleration discriminator ARD and the deceleration discriminator ALD, and the acceleration signal CR or deceleration signal CL is output in the same manner as described above regarding the operation of the speed governors A and B. The aforementioned acceleration signal CR and deceleration signal CL, together with the acceleration signals AR, BR and deceleration signals AL, BL calculated in each governor, are the first and second 2/3
It is supplied to logic circuits (generally majority logic circuits) MJ1 and MJ2. The output of the first 2/3 logic circuit MJ1 is supplied to the first and second mismatch circuits UCN1 and UCN2, while the output of the second 2/3 logic circuit MJ2 is fed to the third and fourth mismatch circuits UCN1 and UCN2. Circuits UCN3 and UCN4
is supplied to Further, the deceleration signal AL from the speed governor A is sent to the first mismatch circuit UCN1, and the deceleration signal AL from the governor A is sent to the first mismatch circuit UCN1.
2 receives the deceleration signal BL from the governor B, and the third discrepancy circuit UCN3 receives the acceleration signal AR from the governor A.
However, the fourth mismatch circuit UCN4 also has governor B.
An acceleration signal BR is supplied from each. First and third mismatch circuits UCN1, UCN3
The output of is supplied to the first OR gate OR1,
On the other hand, the second and fourth mismatch circuits UCN2,
The output of UCN4 is supplied to the second OR gate OR2. Also, the output of the first OR gate OR1 is the first
is added to the AND gate AND1, and the output of the second OR gate OR2 is added to the second AND gate AND1.
Added to 2. As is clear from what will be described later, governor A
When is abnormal, a logic output "1" is produced at the first AND gate AND1, and when governor B is abnormal, a logic output "1" is produced at the second AND gate AND2. Table 1 is a truth table of logical operations performed in the monitoring circuit C of FIG. Note that the X marks in Table 1 indicate that "1" and "0" of the corresponding signals are the results of logical operations (outputs of AND gates AND1 and AND2).
It shows that it is unrelated. Next, with reference to Table 1, the operation of the monitoring circuit C shown in FIG. 4 will be explained for some typical cases. Case 1 The difference between the combined valve opening command signals 8 and 8 output from the governors A and B is small, and the output of the comparator COMP (Fig. 3) is "0" - that is, the start signal ABd
When is “0”, two logics are applied regardless of the output of acceleration discriminator ARD and deceleration discriminator ALD.

[Table] The outputs of product gates AND1 and AND2 are both “0”
It is. Under this condition, no abnormality occurs in governors A and B, and therefore, the governors are not switched. Case 3 Start signal ABd is “1” and governor A deceleration signal
AL becomes “1”, and on the other hand, the acceleration of monitoring circuit C
The deceleration signals CR and CL are both "0". (According to signal 8 from governor A, the turbine is supposed to decelerate, but the actual turbine speed is neither acceleration nor deceleration, indicating that governor A is not operating normally. Become). In this case, the first and second 2/3 logic circuits MJ
The outputs of MJ1 and MJ2 are both "0", and only the third mismatch circuit, UCN3, produces a "1" output. As a result, the outputs of the first OR gate OR1 and the first AND gate AND1 are “1”.
becomes. As a result, it is determined that governor A is abnormal, and when governor A is included in the control system, control is switched to governor B. Case 6 When the start signal ABd is "1", governor B does not generate either acceleration/deceleration signals AR or AL, and the deceleration signal AL of governor A becomes "1", while the monitoring circuit C
In this case, the deceleration signal CL becomes "1". (According to signal 8 of governor B, the turbine is supposed to neither accelerate nor decelerate, but the actual turbine speed is decelerated. Therefore, governor B is not normal. According to signal 8 of speed machine A,
(The speed governor A is operating normally.) In this case, only the outputs of the first 2/3 logic circuit MJ1 and the second mismatch circuit UCN2 become "1". Therefore, the outputs of the second OR gate OR2 and the second AND gate AND2 become "1", and it is determined that the speed governor B is abnormal. Case 9 When the start signal ABd is "1", the acceleration signal BR of governor B and the deceleration signal AL of governor A become "1", while the deceleration signal CL in the monitoring circuit becomes "1".
This is the case when it becomes. (According to signal 8 from governor B, the turbine should be in an accelerating state, but the actual turbine speed is decelerating, and governor B is abnormal.On the other hand, governor A's According to signal 8, it is in a deceleration state and governor A is normal). In this case, the output of the first 2/3 logic circuit MJ1 becomes "1", and the output of the second and fourth mismatch circuits UCN
2. The output of UCN4 becomes "1". Therefore, the outputs of the second OR gate OR2 and the second AND gate AND2 become "1", and it is determined that the speed governor B is abnormal. As can be easily understood from the above explanation of operation and Table 1, the monitoring circuit shown in Fig. 4 performs the following logical operations to determine which governor is abnormal. It's summery. (1) Acceleration signals AR each calculated separately,
Find the majority logic for BR, CR and deceleration signals AL, BL, CL. (2) Find acceleration signals and/or deceleration signals that do not match the output of each majority logic, and determine that the governor generating the acceleration/deceleration signals that do not match is abnormal. (Effects) As is clear from the above explanation, according to the present invention, the self-failure of a pair of speed governors A and B, which greatly affects the reliability of the electro-hydraulic speed governor of the one-standby dynamic switching type, If the detection rate is not 100% (e.g. 95%)
However, by providing a simple monitoring circuit C, the systematic failure detection rate can be improved to over 99%. As a result, for example, MTBF (Mean Time
Between Failure) can be improved by 20%. In addition, the cost required to add the monitoring circuit shown in Figure 4 and the acceleration/deceleration discriminator shown in Figure 3 is approximately 5 to 50%.
It is about 10%, and the ratio of reliability improvement to input cost is large. (Modified Example) In the above embodiment, the monitoring circuit and the set of speed governors A and B were made to perform acceleration rate calculation, but the invention is not limited to this calculation, and other appropriate calculations may be performed. That's a good reason. In the above embodiment, the reason for calculating the acceleration rate is as follows. (1) The acceleration rate is an index value related to the speed signal, which is important for the turbine. (2) Since the turbine speed signal is taken in, there is no need to install a new detector, and the detector Must be able to be used effectively.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an electro-hydraulic speed governor in a steam turbine, FIG. 2 is a block diagram showing a 1-standby dynamic switching system, and FIG. 3 is a block diagram showing a speed governor according to an embodiment of the present invention. Block Diagram FIG. 4 is a block diagram of a monitoring circuit according to one embodiment of the present invention. 1... Turbine actual rotation speed signal, 2... Turbine target rotation speed signal, 3... Speed deviation signal, 4... Load setting signal, 5... Output signal of adder AD2, 8... Turbine integrated valve opening command signal, ABd ...Start signal,
AL, BL, CL...Deceleration signal, AR, BR, CR...Acceleration signal, ACS...Acceleration rate calculator, ALD...Deceleration discriminator, ARD...Acceleration discriminator, COMP...Comparator, MJ
1, MJ2...2/3 logic circuit, UCN1 to UCN4...mismatch circuit, OR1, OR2...OR gate, AND
1, AND2...AND gate.

Claims (1)

[Scope of Claims] 1. A device that is supplied with the actual rotational speed of a steam turbine, generates a turbine joint valve opening command based on the deviation of the actual rotational speed from a target rotational speed of the steam turbine, and a target load; The speed governor that controls the openings of the various steam valves of the steam turbine based on the joint valve opening command is configured in a dual system, one of which is used for actual steam valve control, and the other is used as a standby system. A regulator device for a steam turbine system, which is installed independently in each governor, takes in the turbine steam valve opening command of each governor, and calculates the turbine acceleration rate based on this. first and second generating first and second acceleration/deceleration signals;
a comparator that takes in and compares the turbine steam valve opening commands corresponding to each other for each governor and generates a start signal when the difference between the two commands exceeds a predetermined level; a third acceleration rate calculation means that takes in the actual rotational speed of the turbine, calculates the actual acceleration rate of the turbine based on this, and generates a third acceleration/deceleration signal; a first majority logic circuit that calculates majority logic; a second majority logic circuit that calculates majority logic of the first to third acceleration signals; outputs of the first and second majority logic circuits; Taking in the outputs of the first and second acceleration rate calculation means,
means for performing a scheduled logical operation based on these and outputting a speed governor abnormality determination signal; and means for prohibiting output of the speed governor abnormality determination signal when the start signal is not generated from the comparator. A speed governor device for a steam turbine, characterized by comprising: 2. The first to third acceleration rate calculation means and the first and second majority logic circuits are started in response to generation of the activation signal. A speed governor device for a steam turbine as described in . 3. The predetermined logical operation in the means for outputting the governor abnormality determination signal determines that the speed governor that is generating acceleration/deceleration signals that do not match the outputs of the first and second majority logic circuits is abnormal. A speed governor device for a steam turbine according to claim 1 or 2, characterized in that the speed governor device for a steam turbine is such that it is determined that: