阅读说明：本技术 核电站gss系统抽汽逆止阀逻辑控制方法 (Logical control method for steam extraction check valve of GSS (gas insulated switchgear) system of nuclear power station ) 是由 刘立华 于 2020-11-19 设计创作，主要内容包括：本发明涉及核电厂蒸汽系统技术领域,公开了一种核电站GSS系统抽汽逆止阀逻辑控制方法,其方法包括：当满足单控条件时,触发抽汽逆止阀执行关闭操作；单控条件包括：所述抽汽逆止阀处于非全关状态,且汽水分离再热器系统的组合状态信号为1；或,试验按钮信号取反后为1,且至少一个疏水器液位高信号为1；或,至少一个甩负荷信号,或者试验按钮信号为1。本发明分别设置了单控条件和双控条件,在单控条件和双控条件中,均设置了若干个信号判断子条件,通过单控条件和双控条件的数字化判断,确定抽汽逆止阀是否执行关闭,实现了抽汽逆止阀控制的数字化改造,有效降低了控制站共模失效风险。(The invention relates to the technical field of steam systems of nuclear power plants, and discloses a logical control method for a steam extraction check valve of a GSS (gas recovery system) system of a nuclear power plant, which comprises the following steps: when the single control condition is met, triggering the steam extraction check valve to execute closing operation; the single control condition comprises the following steps: the steam extraction check valve is in a non-fully-closed state, and a combined state signal of the steam-water separation reheater system is 1; or, the signal of the test button is 1 after being negated, and the high signal of the liquid level of at least one steam trap is 1; or at least one load dump signal, or the test button signal is 1. The invention respectively sets a single control condition and a double control condition, sets a plurality of signal judgment sub-conditions in the single control condition and the double control condition, and determines whether the steam extraction check valve is closed or not through the digital judgment of the single control condition and the double control condition, thereby realizing the digital transformation of the control of the steam extraction check valve and effectively reducing the common mode failure risk of the control station.)

1. A nuclear power station GSS system steam extraction check valve logic control method is characterized by comprising the following steps:

when the single control condition is met, triggering the steam extraction check valve to execute closing operation;

the single control condition comprises the following steps:

the steam extraction check valve is in a non-fully-closed state, and a combined state signal of the steam-water separation reheater system is 1; or the like, or, alternatively,

the signal of the test button is 1 after negation, and the high signal of the liquid level of at least one steam trap is 1; or the like, or, alternatively,

at least one of the load dump signals, or the test button signal, is 1.

2. The logical control method of the extraction check valve of the GSS system of the nuclear power plant as claimed in claim 1, wherein when a combined state signal judgment condition is satisfied, the combined state signal of the moisture separator reheater system is 1, and the combined state signal judgment condition includes:

at least one steam turbine trip signal is 1, or,

at least one steam trap level high signal is 1, or,

the bleed reheat control signal is 1.

3. The logical control method for the steam extraction check valve of the GSS system in the nuclear power plant as claimed in claim 1, wherein the triggering the steam extraction check valve to execute the closing operation when the single control condition is satisfied comprises the following steps:

when the single control condition is met, a D0 signal is output to an isolation relay on the low-voltage circuit, a magnetic control switch on the high-voltage circuit is controlled through the isolation relay to be in a closed state, and at the moment, the steam extraction check valve is closed through a pneumatic mechanism on the high-voltage circuit.

4. The logical control method of the steam extraction check valve of the GSS system of the nuclear power plant as claimed in claim 3, wherein the current of the low-voltage circuit is direct current, and the voltage is 48V.

5. The logical control method of the steam extraction check valve of the GSS system of the nuclear power plant as claimed in claim 3, wherein the current of the high-voltage circuit is direct current, and the voltage is 125V.

6. A nuclear power station GSS system steam extraction check valve logic control method is characterized by comprising the following steps:

when the double control condition is met, triggering the steam extraction check valve to execute closing operation;

the double control condition comprises:

the signal D01 output by control station a is 1, or,

the signal D02 output by the control station B is 1.

7. The nuclear power plant GSS system extraction check valve logic control method of claim 6, wherein the double control condition comprises a first double control sub-condition;

when the first dual-control sub-condition is satisfied, the signal D01 output by the control station a is 1, and the first dual-control sub-condition includes:

the steam extraction check valve is in a non-fully-closed state, and a combined A state signal of the steam-water separation reheater system is 1; or the like, or, alternatively,

the load dump signal a is 1, or,

the test button signal is 1, or,

the signal of the test button is 1 after being inverted, and the high signal A of the liquid level of the steam trap is 1.

8. The logical control method of the extraction check valve of the GSS system of the nuclear power plant as claimed in claim 7, wherein when a combined a state signal determination condition is satisfied, the combined a state signal of the moisture separator reheater system is 1, and the combined a state signal determination condition includes:

the steam trip signal is a1, or,

the high signal A of the liquid level of the steam trap is 1, or,

the extraction reheat control signal is 1.

9. The nuclear power plant GSS system extraction check valve logic control method of claim 6, wherein the double control condition comprises a second double control sub-condition;

when a second dual-control sub-condition is satisfied, the signal D02 output by the control station B is 1, where the second dual-control sub-condition includes:

the steam extraction check valve is in a non-fully-closed state, and a combined B state signal of the steam-water separation reheater system is 1; or the like, or, alternatively,

the load dump signal B is 1, or,

the high signal B of the steam trap liquid level is 1.

10. The logical control method of the extraction check valve of the GSS system of the nuclear power plant as claimed in claim 9, wherein when a combined B state signal judgment condition is satisfied, the combined B state signal of the moisture separator reheater system is 1, and the combined B state signal judgment condition includes:

the steam turbine trip signal B is 1, or,

the high signal B of the liquid level of the steam trap is 1.

11. The nuclear power plant GSS system steam extraction check valve logic control method as claimed in claim 6, wherein when the double control condition is satisfied, triggering the steam extraction check valve to execute a closing operation comprises:

when the double-control condition is met, the signal D01 and/or the signal D02 are output to an isolation relay on a low-voltage circuit, a magnetic control switch on a high-voltage circuit is controlled through the isolation relay to be in a closed state, and at the moment, the steam extraction check valve is closed through a pneumatic mechanism on the high-voltage circuit.

12. The logical control method of the extraction check valve of the GSS system of the nuclear power plant as claimed in claim 11, wherein the current of the low voltage circuit is dc and the voltage is 48V.

13. The method of claim 11, wherein the current of the high voltage circuit is dc and the voltage is 125V.

Technical Field

The invention relates to the technical field of steam systems of nuclear power plants, in particular to a logical control method for a steam extraction check valve of a GSS (steam generation system) of a nuclear power plant.

Background

The extraction check valve of a moisture separator reheater system (GSS) assumes an important protection function and needs to be closed quickly in transient states such as tripping and load shedding of a steam turbine.

Taking a reference power plant conventional island as an example, the steam extraction check valve is an inclined disc valve. When there is no flow in the pipe, the valve is closed by the inclined valve seat under the action of gravity. In the full flow state of the pipeline, a pneumatic mechanism controlled by an electromagnetic valve (EL) can forcibly close the valve. When the electromagnetic valve is demagnetized, compressed air enters the pneumatic head, and the compression spring loads the pneumatic mechanism to open the valve under the action of flow. When the electromagnetic valve is excited, the air supply in the pneumatic head is quickly discharged, and the spring-loaded piston drives the valve clack to close the valve. The control of the steam extraction check valve depends on a relay logic control cabinet in a control station, and high common-mode failure risk of the control station exists.

Disclosure of Invention

Therefore, in order to solve the technical problem, it is necessary to provide a logical control method for a steam extraction check valve of a GSS system of a nuclear power plant to reduce the risk of common mode failure of a control station.

A logic control method for a steam extraction check valve of a GSS system of a nuclear power station comprises the following steps:

when the single control condition is met, triggering the steam extraction check valve to execute closing operation;

the single control condition comprises the following steps:

the steam extraction check valve is in a non-fully-closed state, and a combined state signal of the steam-water separation reheater system is 1; or the like, or, alternatively,

the signal of the test button is 1 after negation, and the high signal of the liquid level of at least one steam trap is 1; or the like, or, alternatively,

at least one of the load dump signals, or the test button signal, is 1.

A logic control method for a steam extraction check valve of a GSS system of a nuclear power station comprises the following steps:

when the double control condition is met, triggering the steam extraction check valve to execute closing operation;

the double control condition comprises:

the signal D01 output by control station a is 1, or,

the signal D02 output by the control station B is 1.

According to the logic control method for the steam extraction check valve of the GSS system of the nuclear power station, the single control condition and the double control condition are respectively set, the signal judgment sub-conditions are set in the single control condition and the double control condition, whether the steam extraction check valve is closed or not is determined through digital judgment of the single control condition and the double control condition, digital transformation of control of the steam extraction check valve is achieved, and common mode failure risk of a control station is effectively reduced.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments of the present invention will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive labor.

FIG. 1 is a schematic diagram of a single control station logic control of a steam extraction check valve of a GSS system of a nuclear power plant according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an IO interface of a single control station of a steam extraction check valve of a GSS system of a nuclear power station according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a double-control-station logic control of a steam extraction check valve of a GSS system of a nuclear power plant according to an embodiment of the present invention;

fig. 4 is a schematic diagram of an IO interface of a double control station of an extraction check valve of a GSS system of a nuclear power plant in an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, fig. 1 is a schematic diagram of logic control of a single control station of an extraction check valve of a GSS system of a nuclear power plant according to this embodiment. The logical control method for the steam extraction check valve of the GSS system of the nuclear power station provided by the embodiment comprises the following steps:

when the single control condition is met, triggering the steam extraction check valve to execute closing operation;

the single control condition comprises the following steps:

the steam extraction check valve is in a non-fully-closed state, and a combined state signal of the steam-water separation reheater system is 1; or the like, or, alternatively,

the signal of the test button is 1 after negation, and the high signal of the liquid level of at least one steam trap is 1; or the like, or, alternatively,

at least one of the load dump signals, or the test button signal, is 1.

In this embodiment, the nuclear power station GSS system controls the steam extraction check valve through the single control station, thereby realizing digital modification of steam extraction check valve control. In the logical control method for the steam extraction check valve of the GSS system of the nuclear power station, signal acquisition, logical operation and drive output are realized by a single DCS (digital control system).

The control station is provided with a plurality of logic processing units for processing state signals collected from a GSS system of the nuclear power station. Wherein the status signal includes a steam extraction isolation signal (for reflecting whether the steam extraction check valve is in a non-fully closed state, if the steam extraction check valve is not in a non-fully closed state, the signal is 0, if the steam extraction check valve is in a non-fully closed state, the signal is 1), a steam turbine trip signal a (indicating a steam turbine trip signal of the row a, the same below), a steam turbine trip signal B, a steam trap liquid level high signal a (indicating that, in the row a, if the steam trap liquid level is high, the signal is 1, if the steam trap liquid level is not high, the signal is 0, the "high" is the liquid level of the steam trap, in one example, the liquid level of the steam trap can be divided into high, medium, low and low, the same below), a steam trap liquid level high signal B, an extraction reheating control signal (a signal for monitoring an extraction reheating state), and a load rejection signal a (a state of the steam trap system a row, the same below), a load shedding signal B, a test button signal (the test button has two states, when the test button is in a non-test state, the signal is 0, and when the test button is in a test state, the signal is 1), a steam trap liquid level high signal A and a steam trap liquid level high signal B.

The combined state signal comprises the steam turbine tripping signal A, the steam turbine tripping signal B, the steam trap liquid level high signal A, the steam trap liquid level high signal B and the extraction reheating control signal.

The single control condition may refer to a signal condition that triggers the steam extraction check valve to perform a closing operation. Specifically, the single control condition comprises the following sub-conditions:

sub-condition 1: the steam extraction check valve is in a non-fully-closed state, and a combined state signal of the steam-water separation reheater system is 1;

sub-condition 2: the signal of the test button is 1 after negation, and the high signal of the liquid level of at least one steam trap is 1;

sub-condition 3: at least one of the load dump signals, or the test button signal, is 1.

When any of the sub-conditions is met, the steam extraction check valve can be triggered to execute closing operation. Here, the single control condition is a condition when the single control station output signal is 1.

The single control condition is set in the embodiment, a plurality of signal judgment sub-conditions are set in the single control condition, whether the steam extraction check valve is closed or not is determined through digital judgment of the single control condition, and digital transformation of steam extraction check valve control is achieved.

Optionally, when the combined state signal determination condition is satisfied, the combined state signal of the moisture separator reheater system is 1, and the combined state signal determination condition includes:

at least one steam turbine trip signal is 1, or,

at least one steam trap level high signal is 1, or,

the bleed reheat control signal is 1.

In this embodiment, at least one steam turbine trip signal is 1, which means that the steam turbine trip signal a and/or the steam turbine trip signal B is 1. Similarly, at least one steam trap level high signal is 1, meaning that steam trap level high signal A and/or steam trap level high signal B is 1. Referring to fig. 1, when any one of the five signals is 1, the combination status signal is 1.

Optionally, when the single control condition is satisfied, triggering the steam extraction check valve to execute a closing operation, including:

when the single control condition is met, a D0 signal is output to an isolation relay on the low-voltage circuit, a magnetic control switch on the high-voltage circuit is controlled through the isolation relay to be in a closed state, and at the moment, the steam extraction check valve is closed through a pneumatic mechanism on the high-voltage circuit.

Understandably, the D0 signal is the output signal of the single control station. The D0 signal may be 0 or 1. When the single control condition is satisfied, the D0 signal is 1. When the single control condition is not met, the D0 signal is 0.

As shown in fig. 2, fig. 2 is a schematic view of an IO interface of a single control station of an extraction check valve of a GSS system of a nuclear power plant according to an embodiment of the present invention. When the single control condition is met, a D0 signal with a signal value of 1 is transmitted to an isolation relay on the low-voltage circuit, and the isolation relay controls a magnetic control switch on the high-voltage circuit to enable the magnetic control switch to be in an on-state. At this time, the steam extraction check valve is closed by a pneumatic mechanism on the high-voltage circuit. That is, when the isolation relay is in the passage, the magnetic control switch is also in the closed state, at the moment, the high-voltage loop is in the communicated state, the pneumatic mechanism on the high-voltage circuit starts to work, the air supply in the pneumatic head is quickly discharged, and the spring-loaded piston drives the valve clack to close the steam extraction check valve. When the isolating relay is in an open circuit, the magnetic control switch is also in a disconnected state, the high-voltage loop is in a disconnected state, compressed air enters the pneumatic head, and the compression spring loads the pneumatic mechanism to enable the steam extraction check valve to be opened under the action of flow.

Optionally, the current of the low-voltage circuit is direct current, and the voltage is 48V.

Understandably, the low-voltage circuit can be powered by a direct current power supply. In one example, the power supply of the dc power supply is 48V.

Optionally, the current of the high-voltage circuit is direct current, and the voltage is 125V.

Understandably, the high voltage circuit may be powered by a dc power source. In one example, the dc power source has a power supply of 125V.

The steam extraction check valve control logic comprises: protection logic signals (steam turbine tripping, load shedding, liquid level of a drain tank and the like), steam extraction reheating control signals and valve closing test signals. The following reliability analysis was performed for the protection off logic of GSS109VV (i.e., without regard to the valve shut down test button and extraction reheat control).

Suppose that: p is a radical of₁、q₁The probability of the refusal action and the misoperation caused by the abnormity of the switching value signals (the liquid level switch and the valve position switch); p is a radical of₂、q₂The probabilities of operation rejection and misoperation caused by the abnormal tripping and load shedding signals of the steam turbine are respectively; p is a radical of₃、q₃Respectively indicating the probability of the failure and the misoperation caused by the abnormal condition of a redundant processor of the DCS control station (such as the abnormal phenomena of control output error caused by the abnormal condition of the redundant processor, the abnormal switching of a main processor and a slave processor, the abnormal condition of the DCS station and the like due to the abnormal operation of the DCS station and the like), or the fault of an output card DO, or the abnormal condition of an isolation relay XR and the like; p is a radical of₄、q₄Respectively the probability of the failure of the electromagnetic valve and the probability of the misoperation caused by the abnormal power supply.

As shown in fig. 3, fig. 3 is a schematic diagram of logic control of a steam extraction check valve dual control station of the GSS system of the nuclear power plant according to this embodiment. The embodiment of the invention also provides a logical control method for the steam extraction check valve of the GSS system of the nuclear power station, which comprises the following steps:

when the double control condition is met, triggering the steam extraction check valve to execute closing operation;

the double control condition comprises:

the signal D01 output by control station a is 1, or,

the signal D02 output by the control station B is 1.

Understandably, the GSS system of the nuclear power station controls the steam extraction check valve through the double control stations, and realizes the digital modification of the control of the steam extraction check valve. In the logical control method for the steam extraction check valve of the GSS system of the nuclear power station, two DCS (digital control system) control stations are used for realizing signal acquisition, logical operation and drive output. The two DCS control stations are control station a and control station B, respectively.

The control station A is provided with a plurality of logic processing units for processing state signals collected from a nuclear power plant GSS system A column. The logic processing unit is used for processing the multipath state signals into a single output signal. Wherein, the state signal of the row a includes a steam extraction isolation signal (for reflecting whether the steam extraction check valve is in a non-fully-closed state, if the steam extraction check valve is not in a non-fully-closed state, the signal is 0, if the steam extraction check valve is in a non-fully-closed state, the signal is 1), a steam turbine trip signal a (representing a steam turbine trip signal of the row a, the same below), a steam trap liquid level high signal a (representing that, in the row a, if the steam trap liquid level is in a high level, the signal is 1, if the steam trap liquid level is not in a high level, the signal is 0, the "high" is the liquid level of the steam trap, in one example, the liquid level of the steam trap can be divided into high, medium, low and low, the same below), a pumping reheating control signal (for monitoring the pumping state), a load shedding signal a (a state of the steam-water separation reheater system row a, the same below), The signal of the test button (the test button has two states, when the test button is in a non-test state, the signal is 0, and when the test button is in a test state, the signal is 1), and the high signal A of the steam trap liquid level.

The control station B is provided with a plurality of logic processing units for processing the state signals collected from the GSS system B column of the nuclear power plant. The logic processing unit is used for processing the multipath state signals into a single output signal. The state signals of the B row comprise steam extraction isolation signals (used for reflecting whether the steam extraction check valve is in a non-fully-closed state, if the steam extraction check valve is not in the non-fully-closed state, the signals are 0, and if the steam extraction check valve is in the non-fully-closed state, the signals are 1), steam turbine tripping signals B, steam trap liquid level high signals B, load shedding signals B and steam trap liquid level high signals B.

The double control condition may refer to a signal condition that triggers the steam extraction check valve to perform a closing operation. Specifically, the dual control condition includes the following sub-conditions:

sub-condition 1: the signal D01 output by control station a is 1,

sub-condition 2: the signal D02 output by the control station B is 1.

When any of the sub-conditions is met, the steam extraction check valve can be triggered to execute closing operation. Here, the double control condition is a condition when the control station a and/or the control station B output signal is 1.

The embodiment is provided with a double-control condition, a plurality of signal judgment sub-conditions are also set in the double-control condition, whether the steam extraction check valve is closed or not is determined through digital judgment of the double-control condition, and digital modification of control of the steam extraction check valve is realized.

Optionally, the dual-control condition includes a first dual-control sub-condition;

when the first dual-control sub-condition is satisfied, the signal D01 output by the control station a is 1, and the first dual-control sub-condition includes:

the steam extraction check valve is in a non-fully-closed state, and a combined A state signal of the steam-water separation reheater system is 1; or the like, or, alternatively,

the load dump signal a is 1, or,

the test button signal is 1, or,

the signal of the test button is 1 after being inverted, and the high signal A of the liquid level of the steam trap is 1.

Understandably, the first dual-control sub-condition may refer to a determination condition of a column state signal of the GSS system a of the nuclear power plant. The first dual-control sub-condition comprises four sub-conditions, which are respectively:

1. the steam extraction check valve is in a non-fully-closed state, and a combined A state signal of the steam-water separation reheater system is 1;

2. the load shedding signal a is 1 and,

3. the test button signal is a1 and,

4. the signal of the test button is 1 after being inverted, and the high signal A of the liquid level of the steam trap is 1.

When any one of the above sub-conditions is satisfied, the first dual-control sub-condition may be satisfied. When the steam extraction check valve is in a non-fully closed state, the corresponding steam extraction isolation signal is 0. The combined a-state signal of the moisture separator reheater system may refer to a result signal output by a logic processing unit for processing a steam turbine trip signal a, a steam trap liquid level high signal a, and a steam extraction reheating control signal.

Optionally, when the combined a state signal determination condition is satisfied, the combined a state signal of the moisture separator reheater system is 1, and the combined a state signal determination condition includes:

the trip signal of the steam turbine is 1, or,

the high and high signal of the liquid level of the steam trap is 1, or,

the extraction reheat control signal is 1.

Understandably, the combined a-state signal determination condition includes three sub-conditions, which are:

1. the trip signal of the steam turbine is 1,

2. the high signal of the liquid level of the steam trap is 1,

3. the extraction reheat control signal is 1.

When any one of the above sub-conditions is satisfied, the combined a state signal judgment condition is satisfied. When the combined A state signal judgment condition is satisfied, the output signal is 1; when the combined a state signal determination condition is not satisfied, the output signal is 0.

Optionally, the dual-control condition includes a second dual-control sub-condition;

when a second dual-control sub-condition is satisfied, the signal D02 output by the control station B is 1, where the second dual-control sub-condition includes:

the steam extraction check valve is in a non-fully-closed state, and a combined B state signal of the steam-water separation reheater system is 1; or the like, or, alternatively,

the load dump signal B is 1, or,

the high signal B of the steam trap liquid level is 1.

Understandably, the second dual-control sub-condition may refer to a judgment condition of a B-column status signal of the GSS system of the nuclear power plant. The second dual-control sub-condition comprises three sub-conditions, which are respectively:

1. the steam extraction check valve is in a non-fully closed state, and a combined B state signal of the steam-water separation reheater system is 1;

2. the load shedding signal B is 1 and the load shedding signal B,

3. the high signal B of the steam trap liquid level is 1.

When any one of the above sub-conditions is satisfied, the second dual-control sub-condition may be satisfied. When the steam extraction check valve is in a non-fully closed state, the corresponding steam extraction isolation signal is 0. The combined B state signal of the moisture separator reheater system may refer to a result signal output by a logic processing unit for processing a steam turbine trip signal and a steam trap liquid level high signal.

Optionally, when the combined B state signal determination condition is satisfied, the combined B state signal of the moisture separator reheater system is 1, and the combined B state signal determination condition includes:

the trip signal of the steam turbine is 1, or,

the high signal of the liquid level of the steam trap is 1.

Understandably, the combined B-state signal determination condition includes two sub-conditions, respectively:

1. the trip signal of the steam turbine is 1,

2. the high signal of the liquid level of the steam trap is 1.

When any one of the above sub-conditions is satisfied, the combined B-state signal determination condition is satisfied. When the combined B state signal judgment condition is satisfied, the output signal is 1; when the combined B state signal determination condition is not satisfied, the output signal is 0.

Optionally, when the dual control condition is satisfied, triggering the steam extraction check valve to execute a closing operation, including:

when the double-control condition is met, the signal D01 and/or the signal D02 are output to an isolation relay on a low-voltage circuit, a magnetic control switch on a high-voltage circuit is controlled through the isolation relay to be in a closed state, and at the moment, the steam extraction check valve is closed through a pneumatic mechanism on the high-voltage circuit.

Understandably, the D0 signal is the output signal of the single control station. The D0 signal may be 0 or 1. When the single control condition is satisfied, the D0 signal is 1. When the single control condition is not met, the D0 signal is 0.

As shown in fig. 4, fig. 4 is a schematic view of an IO interface of a dual control station of an extraction check valve of a GSS system of a nuclear power plant according to an embodiment of the present invention. When the double control condition is met, the signal D01 and/or the signal D02 with the signal value of 1 are transmitted to an isolation relay on the low-voltage circuit, and the magnetic control switch on the high-voltage circuit is controlled through the isolation relay to enable the magnetic control switch to be in an on-state. At this time, the steam extraction check valve is closed by a pneumatic mechanism on the high-voltage circuit. That is, when the isolation relay is in the passage, the magnetic control switch is also in the closed state, at the moment, the high-voltage loop is in the communicated state, the pneumatic mechanism on the high-voltage circuit starts to work, the air supply in the pneumatic head is quickly discharged, and the spring-loaded piston drives the valve clack to close the steam extraction check valve. When the isolating relay is in an open circuit, the magnetic control switch is also in a disconnected state, the high-voltage loop is in a disconnected state, compressed air enters the pneumatic head, and the compression spring loads the pneumatic mechanism to enable the steam extraction check valve to be opened under the action of flow.

Optionally, the current of the low-voltage circuit is direct current, and the voltage is 48V.

Understandably, the low-voltage circuit can be powered by a direct current power supply. In one example, the power supply of the dc power supply is 48V.

Optionally, the current of the high-voltage circuit is direct current, and the voltage is 125V.

Understandably, the high voltage circuit may be powered by a dc power source. In one example, the dc power source has a power supply of 125V.

And carrying out reliability analysis on the two logic control methods. Specifically, the steam extraction check valve control logic comprises: protection logic signals (steam turbine tripping, load shedding, liquid level of a drain tank and the like), steam extraction reheating control signals and valve closing test signals. The following reliability analysis was performed for the protection-off logic of the extraction check valve (i.e. without considering the valve-closing test button and the extraction reheat control).

Suppose that: p is a radical of₁、q₁The probability of the refusal action and the misoperation caused by the abnormity of the switching value signals (the liquid level switch and the valve position switch); p is a radical of₂、q₂The probabilities of operation rejection and misoperation caused by the abnormal tripping and load shedding signals of the steam turbine are respectively; p is a radical of₃、q₃Respectively indicating the fault of the redundant processor of the DCS control station (such as the abnormal phenomena of control output error caused by the fault of the redundant processor, the abnormal switching of a master processor and a slave processor, the abnormal operation of the DCS station and the like), the fault of an output card DO (used for outputting D0 or D01 and D02 signals), or the fault of an isolation relay XR (X-ray isolation relay) and the probability of malfunction; p is a radical of₄、q₄Respectively the probability of the failure of the electromagnetic valve and the probability of the misoperation caused by the abnormal power supply.

For a single control station, when the liquid level is high or A, B signals of steam turbine tripping or load shedding are failed simultaneously, the protection channel refuses to operate with the probability p₁ ²+2p₂ ²(ii) a When the liquid level is high or the trip signal of the steam turbine normally appears (the probability of appearing is zeta), the valve position of the steam extraction isolation valve is abnormal (a full-closed signal is sent) so that the protection channel is refused to act, and the probability is zeta p₁(ii) a When the DCS control station fails and stops operation or an output card fails or an isolation relay fails and the like, the protection fails and refuses to operate, and the refusing probability is p₃(ii) a The failure of the valve control electromagnetic valve loop causes the failure of the valve to close, and the protection failure probability is p₄。

Thus, the probability of a single control station's action rejection may be: p is a radical of₁ ²+2p₂ ²+ζ*p₁+p₃+p₄。

When the liquid level is high or the steam engine trips or any signal of the A or B row of the load shedding is triggered by mistake, the false action of the protection channel is caused, and the false action probability is 2q₁+4q₂(ii) a When the DCS control station has operation fault or output card fault or isolation relay is abnormal, a '1' signal is output by mistake, the valve is closed by mistake, and the probability of protection misoperation is q₃(ii) a Failure of the valve control solenoid valve circuit, resulting in a valve failureThe door is closed by mistake, and the probability of protecting misoperation is q₄。

Thus, the probability of malfunction of a single control station may be: 2q of₁+4q₂+q₃+q₄。

For the dual control stations, 2 control stations are respectively A, B protection channels, and A, B columns are respectively collected into the corresponding control stations for configuration so as to realize the protection function. When 2 control stations corresponding to the A, B channel are abnormal at the same time, the protection refuses to operate; when any control station corresponding to the A, B channel is abnormal, a valve closing signal is sent out by mistake, and protection misoperation is caused.

When the liquid level of 2 control stations is high or the steam engine tripping or load shedding signals are all invalid, the protection channel refuses to operate, and the probability of the double control stations refusing to operate is p₁ ²+2p₂ ²(ii) a When the liquid level is high or the steam turbine tripping signal normally appears (the probability of appearance is assumed to be zeta), if the steam extraction isolation valve position signal is abnormal, the protection channel is refused to operate, and the probability of double control station refusing to operate is zeta × p₁)²(ii) a Wherein the liquid level of 1 control station is high or the steam turbine tripping or load shedding signal is invalid, the DCS control station superposed with another 1 control station fails to stop running or the output card fails to normally output a '1' signal or the fault contact of the isolation relay cannot be closed, so that the valve cannot be normally protected and closed, and the dual-control station failure probability is 2 (p)₁+2p₂)*p₃(ii) a When 2 DCS control stations are out of order or an output card fails to normally output a '1' signal or a fault contact of an isolation relay cannot be closed, the valve cannot be normally protected and closed, and the dual-control-station failure probability is p₃ ²(ii) a The failure of the valve electromagnetic valve loop causes the valve to be unable to close, and the protection failure probability is p₄。

Thus, the probability of a dual control station's action rejection may be: p is a radical of₁ ²+2p₂ ²+(ζ*p₁)²+2(p₁+2p₂)*p₃+p₃ ²+p₄。

When the liquid level of any control station is high or the steam engine is tripped or the load shedding signal is triggered by mistake, the misoperation of the protection channel and the mistake of the double control stations are causedDynamic probability of 2 (q)₁+2q₂) (ii) a When any DCS control station has operation fault or output card fault or isolation relay is abnormal, a '1' signal is output by mistake, the valve is closed by mistake, and the probability of false operation of double control station protection is 2q₃(ii) a The valve electromagnetic valve loop fault causes the valve to be closed by mistake, and the protection malfunction probability is q₄。

Thus, the dual control station malfunction probability may be: 2q of₁+4q₂+2q₃+q₄。

Through the analysis, the reliability of the single and double control station 2 schemes is compared, and the reliability is shown in table 1.

TABLE 1 list of reliability comparisons for single and dual control stations

According to the table 1, compared with a single control station scheme, the double control station adopts 2 control stations, 2 DO outputs and 2 isolation relays, so that the protection action rejection risk is reduced.

In terms of the false action probability, the double control station scheme has a slightly increased false action probability due to the adoption of 2 control stations, 2 DO outputs and 2 isolation relays. However, it is considered that the occurrence of "1" signal due to abnormality in the DCS control station, the change of the DO output from "0" abnormality to "1", the erroneous closing of the isolation relay contact, and the like are negligible and extremely low.

It should be understood that, the sequence numbers of the steps in the foregoing embodiments do not imply an execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of the functional units and modules is illustrated, and in practical applications, the above-mentioned function distribution may be performed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-mentioned functions.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present invention, and are intended to be included within the scope of the present invention.