A safe and efficient test method for nuclear power plant steam turbine protection channel

Abstract

The present invention belongs to the instrumentation and control technology of nuclear power plants, and specifically relates to a safe and efficient method for testing the protection channel of a nuclear power plant turbine, including optimizing the transmission of the trip protection channel and designing the test logic configuration of the trip protection channel; optimizing the transmission of the trip protection channel means changing all trip protection signals across platforms and controllers from network transmission to hard-wired transmission; designing the test logic configuration of the trip protection channel means adding a test logic function design to the digital configuration. This method greatly reduces the risk of human error during the channel test, avoids degradation of the protection channel, reduces the manpower and time costs in the work, and saves the critical path of overhaul. Starting from the optimization of the transmission mode of the trip protection channel and the design of the channel test logic, the first turbine protection channel test of a domestic nuclear power project was realized.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power plant instrument control technology, and in particular relates to a safe and efficient method for testing a protection channel of a steam turbine in a nuclear power plant. Background Art

[0002] The nuclear power plant steam turbine protection system is used to receive more than 70 trip protection signals from nuclear power plant steam turbine generator unit related systems, reactor protection related systems, electrical relay protection related systems, emergency trip buttons, etc., and perform real-time calculations and processing. When any predetermined fault occurs that affects the safe and stable operation of the unit or steam turbine generator unit, it provides a means of safe shutdown for the steam turbine generator unit to prevent the accident from occurring, expanding and damaging the equipment, and sends the steam turbine trip signal to the reactor shutdown logic and electrical system to ensure that the nuclear power plant units and equipment are quickly evacuated to a safe state.

[0003] To prevent malfunction or failure of steam turbine protection from causing damage to major nuclear power plant equipment, resulting in severe economic losses, or placing the nuclear power plant in an unsafe state, nuclear power plant steam turbine protection systems must meet high reliability requirements. Therefore, steam turbine protection systems must undergo important periodic functional testing, and these tests must not affect normal tripping functions.

[0004] At present, in the nuclear power projects that are already in commercial operation in China, the periodic test method of the digital turbine protection system adopts the method of disconnecting the wiring on the cabinet side or on the local side, injecting simulation signals through the signal generator, combined with forced configuration on the computer center side, and verifying the turbine protection channel and function at the operator station on the computer center side. It is generally carried out once for each overhaul.

[0005] like Figure 1 The traditional test method shown in the figure is as follows: Two testers remove the signal wiring from the field sensor instrument to cabinet 1 or the local instrument side in room 1 and inject a simulated signal using a signal generator. One tester, at the engineer's or operator's station in the computer center in room 3, checks whether the relevant signal is triggered as expected in cabinet 2 in room 1. This tester provides feedback on the test results by phone, and after confirming that the test is normal, the relevant wiring is restored. The next protection channel test is then carried out in sequence.

[0006] This type of method has the following disadvantages: (1) The protection channel test takes a long time for overhaul, and there is a risk of affecting the critical path of overhaul, which is unfavorable to the economy of the unit; (2) The protection channel test requires the participation of multiple people at the same time, requiring 2 people to perform in the cabinet or 2 people to simulate on-site, and 1-2 people to check and record at the engineer station or operator station, resulting in high maintenance costs; 3. Frequent disconnection of wiring during the test may cause terminal block failure and damage, and the cable termination may not be restored or the termination may be unreliable, which may lead to abnormal preventive maintenance and cause protection channel failure. There is also the risk of human error such as signal forcing errors or failure to restore correctly after forcing. Summary of the Invention

[0007] The purpose of the present invention is to provide a safe and efficient nuclear power plant steam turbine protection channel test method, which can avoid protection channel degradation and reduce manpower and time costs in the work.

[0008] The technical solutions of the present invention are as follows:

[0009] A safe and efficient nuclear power plant steam turbine protection channel test method, including trip protection channel transmission optimization and trip protection channel test logic configuration design;

[0010] The aforementioned optimization of the transmission of the trip protection channel refers to changing all the trip protection signals across platforms and controllers from network transmission to hard-wired transmission;

[0011] The aforementioned design of the test logic configuration for the trip protection channel refers to adding a test logic function design to the digital configuration.

[0012] The design of adding test logic functions in the digital configuration refers to adding four logic functions: automatic resetting of test signals, mutual locking of the same protection test signals, priority of trip protection signals over channel test signals, and independence of test signals from trip protection logic.

[0013] The design of adding test logic function in digital configuration is specifically as follows:

[0014] By starting the test button, the protection channel test signal is injected into the S end of the RS trigger, and then output from the Q end of the RS trigger through the switch output card, and transmitted through hard wiring to the input card corresponding to the controller where the trip protection output channel is located. After processing and calculation by the DCS controller, the protection channel test signal is finally fed back, and the feedback signal is displayed through the status indicator light on the test screen of the operator station.

[0015] In the process of realizing automatic resetting of the test signal, the test injection signal is sent to the controller where the trip protection output channel is located through the RS trigger, and at the same time, a 5s-delayed reset instruction is led out to the R end of the RS trigger. The channel trigger signal of the protection channel for 5s is triggered by the test button. After 5s, the channel trip trigger signal is automatically reset.

[0016] In the process of realizing mutual interlocking of the same protection test signal, the three test buttons corresponding to the three redundant channels participating in the same protection are in an interlocked state, that is, after the test button triggers the test signal, the R end of each RS trigger receives the current test status signal of the other two redundant channels. Only one channel test can be executed at a time. When a trip protection channel test is being executed, other channels are not allowed to be tested.

[0017] In the process of realizing that the trip protection signal takes precedence over the test injection signal, the R terminal of each RS trigger receives the real trip signal, and the trip signal is triggered first during the test.

[0018] In the process of realizing the independence of the test function design and the trip protection signal, a non-AND gate is provided at the output end of the protection channel of the tested steam turbine, which receives the test signal and the trip signal.

[0019] After optimizing the transmission of the trip protection channel and designing the test logic configuration for the trip protection channel, the control cabinets of the turbine regulation system, turbine auxiliary system, generator auxiliary system, and steam-water separator reheater system are connected to various redundant measuring instruments. A 2-out-of-3 judgment is performed, and the inverted DO signal is sent out. This signal is hard-wired to the turbine protection system control cabinet for DI acquisition. The turbine protection system control cabinet receives various trip protection signals and performs calculations to obtain control signals.

[0020] The turbine protection control cabinet sends its output signal to a 2-out-of-1 hydraulic actuator. The 2-out-of-1 hydraulic actuator includes two emergency trip pressure relief solenoid valves. If either one loses power, the hydraulic actuator will be shut down urgently. Each emergency trip solenoid valve is powered by two DO cards at the same time. If any one of the DO cards is normal, the solenoid valve can be energized normally.

[0021] The remarkable effects of the present invention are as follows:

[0022] Currently, there are more than 70 protection channel signals, most of which are trip signals from the verification of related system protection channels of other controllers (turbine regulation controller AP1, turbine auxiliary system controller AP3, steam-water separator reheater controller AP4, generator auxiliary system controller AP5). By optimizing the transmission method of turbine protection transmission signals and optimizing the logical configuration design, the risk of human error during channel testing is greatly reduced, the degradation of protection channels is avoided, the manpower and time costs in the work are reduced, and the overhaul critical path is saved.

[0023] Starting from the optimization of the transmission mode of the trip protection channel and the design of the channel test logic, the first steam turbine protection channel test of a domestic nuclear power project was realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the traditional steam turbine protection channel test scheme;

[0025] Figure 2 This is a schematic diagram of the steam turbine control system for the Zhangzhou Nuclear Power Project;

[0026] Figure 3 This is a schematic diagram of the test logic configuration design of the trip protection channel involved in this method;

[0027] Figure 4 This is a schematic diagram of the turbine protection channel test scheme ultimately formed by this method. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0029] A safe and efficient nuclear power plant steam turbine protection channel test method, the method includes the following parts:

[0030] First, optimize the transmission of the trip protection channel;

[0031] In a nuclear power plant in this embodiment, the steam turbine control system includes five pairs of controllers (APs) to implement the automatic control and adjustment functions of the steam turbine-related systems, among which AP1 is used to implement the steam turbine adjustment function, AP2 is used to implement the steam turbine protection function, AP3 is used to implement the steam turbine-related auxiliary system control function, AP4 is used to implement the steam-water separation reheat system control function, and AP5 is used to implement the generator-related auxiliary system control function.

[0032] These five AP pairs are connected via a single-layer ring network, the Plant Bus, for inter-network signal transmission. To ensure the reliability and rapid response of the trip protection function, the existing trip protection logic design was investigated and optimized. Specifically, all cross-platform and controller trip protection signals were transferred from the network to hard-wired transmission.

[0033] After optimization, all turbine protection channels across controllers are changed to hard-wired transmission.

[0034] Second, conduct the test logic configuration design of the trip protection channel.

[0035] After achieving the first part, that is, optimizing all cross-controller protection channels to hard-wired transmission, the test logic configuration design of the trip protection channel is carried out. Specifically, the test logic function design is added to the digital configuration. The design has four new functions: automatic resetting of test signals, mutual interlocking of the same protection test signals, priority of trip protection signals over channel test signals, and independence of test signals from trip protection logic.

[0036] Take the improved steam turbine protection channel of the nuclear power plant as an example. Figure 3 The implementation principle and process of the four functions shown are schematically illustrated. By newly designing a test button and corresponding configuration controls (DO, DI) on the DCS second-level operator screen on the left, the test button can be turned on at the operator station, that is, the protection channel test signal is injected into the S end of the RS trigger. After the output from the Q end of the RS trigger, it passes through the switch output card (DO) and is transmitted through hard wiring to the input card (DI) corresponding to the controller where the trip protection output channel is located. After being processed and calculated by the controller of the original control system, the protection channel test signal is finally fed back to the status indicator light of the operator station test screen on the right.

[0037] In the process of achieving automatic reset of the test signal: the test injection signal is sent to the controller of the trip protection output channel through the RS trigger, and a 5s-delay reset instruction is also drawn to the R end of the RS trigger. When the tester presses the test button on the screen, the channel trigger signal for the protection channel is triggered for 5s. After 5s, the trip trigger signal of the channel is automatically reset. This is achieved from the design perspective: (1) avoiding the risk of human error causing the channel to fail to reset after the test, resulting in the trip protection being downgraded; (2) avoiding the risk of the previous test channel not being reset and continuing to the next channel test, which ultimately leads to the trip protection being malfunctioning.

[0038] To achieve interlocking of test signals for the same protection system, the three test buttons corresponding to the three redundant channels participating in the same protection system are designed to interlock. Because the R terminal of each RS trigger also receives the current test status signals of the other two redundant channels, only one channel can be tested at a time. While a trip protection channel is being tested, the test buttons for the other channels automatically turn gray, preventing the tester from performing any tests. This technically eliminates the risk of human error, such as testing two channels simultaneously and misoperating the trip protection system, due to the previous channel test not completing before the next channel test begins.

[0039] To prioritize the protection trip signal over the test injection signal, each RS trigger also incorporates a real trip signal into its R terminal. During testing, if the protection signal triggers, the test signal output is automatically prevented, giving priority to the trip signal. This allows not only protection channel testing during overhauls but also, if the power plant requires, online testing of trip protection channels during unit operation.

[0040] In the process of realizing the independence of the test function design and the trip protection signal: a NOT-AND gate is designed at the output end of the tested turbine protection channel to receive the test signal and the trip signal separately, thereby realizing complete independence of the test signal and the actual trip signal. Even if the trip signal is triggered during the test, the trip protection function will not be locked due to the ongoing test, and the normal triggering action of the trip protection function will not be affected.

[0041] The traditional steam turbine protection channel testing solution required separate testing personnel on-site / in the cabinet and at the engineer station during testing. Each channel was individually verified by disconnecting wiring, injecting simulated signals, and forcing configurations. The improved solution, however, requires only two personnel to complete the test on the DCS screen at the engineer station, eliminating manual operations such as disconnecting wiring and forcing. This reduces human risks such as forcing errors, failure to release force, disconnection errors, and failure to restore wiring. This significantly reduces the time required for testing steam turbine protection channels.

[0042] by Figure 2 Take the steam turbine control system of the Zhangzhou Nuclear Power Project shown as an example.

[0043] The nuclear power plant turbine control system (TCS), also known as the Turbine Control System (TCS), is primarily used to monitor and control the 14 process systems of a nuclear power plant's steam turbine generators and their auxiliary systems. The TCS system comprises the Siemens T2000 and PCS7 platforms. The fail-safe functions of the turbine control system (TTG) and the turbine protection system (TTP) are implemented through the PCS7-based AS620T system. The TCS system utilizes the SINEC H1 bus for internal communication between instrumentation and control components, as well as external communication with third-party systems. The SINEC H1 bus system consists of a plant bus and a terminal bus, forming a two-layer ring network structure. The plant bus is used for communication between the AS620 and OM690 operation and monitoring systems, as well as the PU / SU of the ES680 engineering system, primarily for field data collection and processing. The control cabinets of each system are also connected to the Plant Bus. AP1 is used to implement the turbine regulation function, AP2 is used to implement the turbine protection function, AP3 is used to implement the turbine-related auxiliary system control function, AP4 is used to implement the steam-water separation and reheating system control function, and AP5 is used to implement the generator-related auxiliary system control function. These five pairs of APs are connected through a ring network Plant Bus to realize mutual signal network transmission.

[0044] After optimization, all cross-controller steam turbine protection channels are changed to hard-wired transmission. After the trip protection channel test logic configuration design is carried out, the hardware structure diagram of the newly designed steam turbine protection channel test scheme is formed, such as Figure 4 shown.

[0045] The left side of this structure diagram shows various redundant measuring instruments involved in the trip protection of each system. After the relevant instruments enter the various control cabinets of the turbine regulation system / turbine auxiliary system / generator auxiliary system / steam-water separator reheater system in the middle of the structure diagram, they perform a 2-out-of-3 judgment, invert the DO signal and send it to the DI of the turbine protection system control cabinet through hard wiring for data acquisition. The turbine protection system control cabinet is used to receive various trip protection signals and perform calculations.

[0046] The hydraulic actuator contains two emergency trip pressure relief solenoid valves. If either valve loses power, the hydraulic actuator will be shut down immediately.

[0047] Each emergency trip solenoid valve is powered by two DO cards at the same time. If any one of the DO cards is normal, the solenoid valve can be energized normally.

[0048] During normal operation of the unit, the two rows of redundant DO cards in the turbine protection control cabinet respectively supply power to the emergency trip pressure relief solenoid valves of all hydraulic actuators on site on the right side of the structure diagram. As long as one line of power supply is normal, the solenoid valve can be guaranteed to work normally with power; when the trip protection conditions of any line are met, the two rows of redundant DO cards will lose power at the same time, and the two trip solenoid valves on site will also lose power at the same time. As long as any one line of power loss is normal, emergency oil drainage can be carried out to realize the function of rapid tripping of the turbine.

[0049] The traditional steam turbine protection channel testing solution previously employed required separate testing personnel, both on-site / in the cabinet and at the engineer station, during testing. Each channel was individually verified by methods such as disconnecting wiring, injecting simulated signals, and configuring forced connections. The improved solution, however, requires only two personnel to complete the test on the engineer station screen, eliminating manual operations such as disconnecting wiring and forcing connections. This reduces human risks such as forced connections errors, failure to release forced connections, incorrect disconnections, and unrestored connections. This significantly reduces the time required for testing steam turbine protection channels.

[0050] In addition to regular testing of the turbine protection channel during overhauls, this innovative solution can also be used for online testing of the turbine protection channel during normal unit operation, making a significant contribution to improving work efficiency, reducing the risk of human error, and shortening the critical path of overhaul delays.

Claims

1. A safe and efficient nuclear power plant steam turbine protection channel test method, characterized by: Including trip protection channel transmission optimization and trip protection channel test logic configuration design; The aforementioned optimization of the transmission of the trip protection channel refers to changing all the trip protection signals across platforms and controllers from network transmission to hard-wired transmission; The said design of the test logic configuration of the trip protection channel refers to adding the test logic function design in the digital configuration; The aforementioned design of adding test logic functions in the digital configuration refers to adding four logic functions: automatic reset of test signals, mutual blocking of the same protection test signals, priority of trip protection signals over channel test signals, and independence of test signals from trip protection logic. The design of adding a test logic function to the digital configuration is specifically to inject the protection channel test signal into the S end of the RS trigger by starting the test button, and then output it from the Q end of the RS trigger through the switch output card, and then transmit it to the input card corresponding to the controller where the trip protection output channel is located through hard wiring. After processing and calculation by the DCS controller, the protection channel test signal is finally fed back, and the feedback signal is displayed through the status indicator light on the test screen of the operator station.

2. A safe and efficient nuclear power plant steam turbine protection channel test method according to claim 1, characterized in that: In the process of realizing automatic resetting of the test signal, the test injection signal is sent to the controller where the trip protection output channel is located through the RS trigger, and at the same time, a 5s-delayed reset instruction is led out to the R end of the RS trigger. The channel trigger signal of the protection channel for 5s is triggered by the test button. After 5s, the channel trip trigger signal is automatically reset.

3. A safe and efficient nuclear power plant steam turbine protection channel testing method according to claim 1, characterized in that: In the process of realizing mutual interlocking of the same protection test signal, the three test buttons corresponding to the three redundant channels participating in the same protection are in an interlocked state, that is, after the test button triggers the test signal, the R end of each RS trigger receives the current test status signal of the other two redundant channels. Only one channel test can be executed at a time. When a trip protection channel test is being executed, other channels are not allowed to be tested.

4. A safe and efficient nuclear power plant steam turbine protection channel testing method according to claim 1, characterized in that: In the process of realizing that the trip protection signal takes precedence over the test injection signal, the R terminal of each RS trigger receives the real trip signal, and the trip signal is triggered first during the test.

5. A safe and efficient nuclear power plant steam turbine protection channel testing method according to claim 1, characterized in that: In the process of realizing the independence of the test function design and the trip protection signal, a non-AND gate is provided at the output end of the protection channel of the tested steam turbine, which receives the test signal and the trip signal.

6. A safe and efficient nuclear power plant steam turbine protection channel testing method according to claim 1, characterized in that: After optimizing the transmission of the trip protection channel and designing the test logic configuration for the trip protection channel, the control cabinets of the turbine regulation system, turbine auxiliary system, generator auxiliary system, and steam-water separator reheater system are connected to various redundant measuring instruments. A 2-out-of-3 judgment is performed, and the inverted DO signal is sent out. This signal is hard-wired to the turbine protection system control cabinet for DI acquisition. The turbine protection system control cabinet receives various trip protection signals and performs calculations to obtain control signals.

7. A safe and efficient nuclear power plant steam turbine protection channel testing method according to claim 6, characterized in that: The turbine protection control cabinet sends its output signal to a 2-out-of-1 hydraulic actuator. The 2-out-of-1 hydraulic actuator includes two emergency trip pressure relief solenoid valves. If either one loses power, the hydraulic actuator will be shut down urgently. Each emergency trip solenoid valve is powered by two DO cards at the same time. If any one of the DO cards is normal, the solenoid valve can be energized normally.

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