KR101915638B1 - Multi-channel valve control and self-diagnosis system - Google Patents

Abstract

The present invention relates to a multi-channel valve control and self-diagnosis system. More specifically, the present invention can be remotely controlled by an on-site operator in a field, and can monitor an operation state of a valve at normal times, thereby enabling a valve operation state, maintenance information, and trouble prevention if the valve installed in power plants, chemical plants, refinery plants, offshore plants and large ships are to be monitored and controlled by an on-site operator (multi-way system).

Description

CHANNEL VALVE CONTROL AND SELF-DIAGNOSIS SYSTEM [0001]

The present invention relates to a multi-channel valve control and self-diagnosis system, and more particularly, to a multi-channel valve control and a self-diagnosis system for monitoring, controlling, and diagnosing a valve in a multi-way system.

A fluid device that controls the flow rate and pressure of a fluid in a facility (such as a plant, such as a power plant, a chemical plant, or an offshore plant) that uses fluid (water, steam, or oil) is called a control valve.

In the conventional plant industry, the valves are operated by applying the valve operation signal in the main control room (plant system control room).

That is, the conventional valve control method operates the valve in a one-way manner.

More specifically, when a field operator confirms the valve operation state and then delivers the current state to the main control operator through wireless communication, the main control operator applies the valve operation signal to the valve to control the valve. If there is a limit switch on the valve to check the position of the valve disc, it is possible to know the start and end state of the valve operation in the main control room, but the state during the valve operation can not be confirmed. That is, the conventional valve control method has a problem in that the operator does not operate the valve when the operation signal is applied to the valve at a remote place in the main control room and a failure occurs at one place in the valve operation signal transmission system. There is a problem in that there is no way to take an immediate action in case of malfunction or safety accident.

In other words, when the valve is not operated, the field operator can not take any action and only reports the valve operation status to the main control operator. Since the valve is not operated, the performance of the plant system may be deteriorated, reliability may be deteriorated, and stoppage may occur. In the system where hot water or chemicals move, there is a problem that a safety accident may occur.

In addition, in the conventional fault diagnosis method, when the operator visually inspects the valve or when abnormal operation is detected, the valve operation is stopped in an emergency or the valve actuator is separately operated by using diagnostic equipment in the maintenance period of the plant system, , Diagnosis of component breakage and leakage, and valve maintenance.

  In particular, in the case of valve leakage, it is difficult to diagnose faults in normal operation of valve, and valve leakage can be confirmed by water pressure test during valve decommissioning maintenance.

When the control valve is closed, fluid may leak due to damage to the seat ring (fixed in the orifice area of the flow path) and plug (opening / closing of the flow path), and if the initial fluid leakage is not detected, Thereby causing an increase in the maintenance cost in industrial facilities.

Although the conventional control valve is locked, the fluid leakage of the control valve through which the fluid flows is mainly detected by human hearing or tactile sense. Such a method has a problem that can be detected only when the state of the valve packing or the seal is significantly deteriorated and the valve leakage is significant.

When a separate fluid leakage detection device is used, a plurality of acoustic sensors are attached to the area where the fluid leakage is suspected (control valve body exterior), and the signal detected by the acoustic sensor is analyzed by the microcomputer, Discloses a technique for notifying whether a valve is leaked through a leak or an alarm sound.

However, such equipment is expensive equipment, and there is a problem in that it is costly to constantly monitor a specific control valve.

Korean Patent No. 10-0387334 discloses a device for detecting a fluid leakage of a valve.

Korean Registered Patent [10-0387334] (Registered Date: May 30, 2003)

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a multi-channel valve control and self-diagnosis system for controlling and diagnosing valves in a multi-way system.

The objects of the embodiments of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description .

In order to accomplish the above object, a multi-channel valve control and self-diagnosis system according to an embodiment of the present invention includes a smart sensor unit having a plurality of sensors used for monitoring the condition of the valve and the actuator, (100); A valve management unit 200 receiving a sensing signal from the smart sensor unit 100 and activating or deactivating the valve 10 according to a valve opening / closing signal; A main controller 300 connected to the valve manager 200 to receive the sensing signal and to transmit a valve opening / closing signal for controlling the opening / closing of the valve 10 to the valve manager 200; And a valve control unit 200 connected to the valve management unit 200 through a wire or wireless connection to receive a sensing signal from the valve management unit 200 and to control the opening and closing of the valve 10, And a portable controller (400) for delivering the portable information.

The smart sensor unit 100 includes a displacement sensor 110 installed at a connection portion 30 between the valve 10 and the actuator 20 to measure the position of the actuator stem 21; A fluid pressure sensor (120) for measuring fluid pressure inside the valve (10); And a thrust sensor (130) installed on the actuator stem (21) for measuring an axial force.

In addition, the valve 10 is given a unique identifier, the portable controller 400 wirelessly identifies the unique identifier of the valve 10, and the valve 10 connected to the valve 10, based on the unique identifier, And is connected to the management unit (200).

The smart sensor unit 100 may further include one or more sensors selected from a sound wave sensor, a voltage sensor, and a temperature sensor.

The valve management unit 200 may include a signal management unit 210 for collecting and storing the sensing signals. And a determination unit 220 for determining whether the valve 10 is normal based on the sensing signal stored in the signal management unit 210 according to the diagnosis algorithm.

Also, the determination unit 220 may determine

Actuator output / Seat ring force <1

) * 변형률(%) * 재료 탄성계수(

), 시트링 포스= 시트링 면적 * 밸브 내부 유체 압력)(Where actuator output = actuator stem cross section (

) * Strain (%) * Material elastic modulus (

), Seat ring force = seat ring area * fluid pressure inside valve)

It is determined that it is abnormal.

The determination unit 220 determines that the graph of the displacement over time after the valve opening / closing signal is transmitted to the main control unit 300 is abnormal when the graph of the displacement exceeds the preset error range in the normal operation range do.

The determination unit 220 determines whether the valve 10 is normal based on the stem vibration generated when the valve is closed.

In addition, the determination unit 220 determines that the temperature is abnormal when the temperature increases or decreases by 40 to 60% or more from the temperature change during operation.

In addition, the determination unit 220 determines that the electrical signal (voltage, current) of the communication module or the signal cable used for communication is abnormal when 20 to 40% or more of the electric signal changes.

According to the multi-channel valve control and self-diagnosis system according to the embodiment of the present invention, the valves installed in power plants (nuclear power plants, thermal power plants, cogeneration plants, etc.), chemical plants, refinery plants, offshore plants, , When the control signal cable delivered from the main control room is damaged, emergency signal must be transmitted to the plant system, when the plant system is to be protected by the occurrence of a safety accident, When the operator needs to monitor and control the valve directly, the operator can remotely adjust the valve in the field, monitor the operation status of the valve during normal operation, and prevent valve operation status, maintenance information, and trouble .

In addition, based on the information sensed by the displacement sensor, the fluid pressure sensor and the Thrust sensor or the information sensed by the displacement sensor, the fluid pressure sensor and the positioner pressure sensor, the actuator output evaluation is performed to determine the force The necessary measures can be transmitted to the main control unit or the portable control unit according to the evaluation result, so that immediate measures can be taken.

In addition, there is an effect that, by assigning a unique identifier to each valve, and managing the valve based on the unique identifier, valve management can be performed easily without prior knowledge of the valve.

Further, by using an additional diagnostic sensor such as a sound wave sensor, a voltage sensor and a temperature sensor, it is possible to determine whether the valve is normal even during operation of the valve.

1 is a block diagram of a multi-channel valve control and self-diagnosis system in accordance with an embodiment of the present invention.
2 is a view showing an example in which a smart sensor unit of a multi-channel valve control and self-diagnosis system according to an embodiment of the present invention is installed and a valve is closed.
3 is a view showing another example in which a smart sensor unit of a multi-channel valve control and self-diagnosis system according to an embodiment of the present invention is installed and a valve is opened.
4 is a block diagram showing a state in which a signal management unit and a determination unit are included in the valve management unit of FIG.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, .

On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term " comprises " or " having ", etc. is intended to specify the presence of stated features, integers, steps, operations, elements, parts, or combinations thereof, And does not preclude the presence or addition of one or more other features, integers, integers, steps, operations, elements, components, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are to be construed as ideal or overly formal in meaning unless explicitly defined in the present application Do not.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concept of the term appropriately in order to describe its own invention in the best way. The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Further, it is to be understood that, unless otherwise defined, technical terms and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Descriptions of known functions and configurations that may be unnecessarily blurred are omitted. The following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms. In addition, like reference numerals designate like elements throughout the specification. It is to be noted that the same elements among the drawings are denoted by the same reference numerals whenever possible.

FIG. 1 is a block diagram of a multi-channel valve control and self-diagnosis system according to an embodiment of the present invention. FIG. 2 is a block diagram of a multi-channel valve control and self- 3 shows another example in which the smart sensor unit of the multi-channel valve control and self-diagnosis system according to the embodiment of the present invention is installed. FIG. 4 is a block diagram showing a state in which the signal management unit and the determination unit are included in the valve management unit of FIG. 1. FIG.

1 and 2, a multi-channel valve control and self-diagnosis system according to an embodiment of the present invention includes a smart sensor unit 100, a valve management unit 200, a main control unit 300, (400).

The smart sensor unit 100 is provided with a plurality of sensors used for monitoring the condition of the valve 10 and the driver 20. [

The smart sensor unit 100 can use various sensors such as a pressure sensor, a displacement sensor, an axial force (thrust) sensor, an ultrasonic sensor, a temperature sensor, a voltage sensor, a current sensor and an acoustic sensor. A suitable sensor can be selected and used.

The valve management unit 200 receives a sensing signal from the smart sensor unit 100 and operates the valve 10 to open and close in response to a valve opening / closing signal.

The valve management unit 200 allows the user to exchange necessary information between the valve 10 and the main control unit 300 or between the valve 10 and the portable control unit 400. The valve management unit 200 receives a signal input from the smart sensor unit 100, The valve 10 can be opened and closed based on a command received from the main control unit 300 or the portable controller 400. [

The main control unit 300 receives the sensing signal from the valve management unit 200 and transmits a valve opening / closing signal to the valve management unit 200 for controlling the opening and closing of the valve 10.

The main control unit 300 may be connected to the valve control unit 200 in a wired or wireless manner and the main control unit 300 may monitor the state of the valve 10 based on the received sensing signal, , The valve 10 can be opened and closed in consideration of the situation of the field, the operation situation, and the like.

The portable control unit 400 is connected to the valve management unit 200 by wire or wirelessly and receives a detection signal from the valve management unit 200 and outputs a valve opening / closing signal for controlling the opening / To the management unit (200).

The portable control unit 400 can monitor the state of the valve 10 based on the received sensing signal as in the main control unit 300. The portable control unit 400 can monitor the state of the valve 10 based on the monitoring result, ) Can be opened and closed.

As the portable controller 400, a portable wired terminal, a portable wireless terminal, a mobile terminal, a tablet, a portable PC, various smart devices, and the like can be used.

In the case of a portable wired terminal, a connector that can be connected to the portable control unit 400 by wire may be formed in the valve management unit 200.

Other wireless terminals include a wireless LAN (WLAN), a wireless fidelity (Wi-Fi), a wireless broadband Internet, a World Interoperability for Microwave Access, a High Speed Downlink Packet Access (HSDPA) Zigbee, Bluetooth, Ultra-wideband, IrDA, UltraWall Band, Shared Wireless Access Protocol (SWAP), Long Term Evolution (LTE) Near Field Communication).

It is also possible to use both wireless communication and wired communication.

This is for the purpose of enabling the monitoring and control of the valve by another communication when any communication is impossible.

The portable control unit 400 can control the state of the valve and the operation of the valve by software of a simple application type.

The portable control unit 400 is provided to allow a field operator to promptly respond to the field. When the valve is not operated or a problem is detected in the valve, the valve operation signal in the main control room is controlled by line disconnection or the like A valve opening / closing signal for controlling the opening / closing of the valve 10 is transmitted to the valve management unit 200 to receive the detection signal from the valve management unit 200 so that the state of the valve can be monitored and controlled, Can be operated.

The smart sensor unit 100 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention may include a displacement sensor 110, a fluid pressure sensor 120, and a thrust sensor 130.

The displacement sensor 110 is installed at the connection portion 30 between the valve 10 and the actuator 20 to measure the position of the actuator stem 21.

The fluid pressure sensor (120) measures the fluid pressure inside the valve (10).

The thrust sensor 130 is installed on the actuator stem 21 to measure axial force.

3, a positioner pressure sensor 140 may be used instead of the thrust sensor 130 to measure the pressure on the actuator positioner 22 side inside the actuator 20. In this case,

The valve 10 of the multi-channel valve control and self-diagnosis system according to the embodiment of the present invention is given a unique identifier,

The portable controller 400 wirelessly identifies the unique identifier of the valve 10 and connects to the valve management unit 200 connected to the valve 10 based on the unique identifier.

In order to connect the valve 10 to the portable controller 400 wirelessly in an area where the valves are concentrated, the corresponding valve 10 requiring monitoring or control must be separately connected. To this end, it is desirable to give a unique identifier to each valve 10.

The smart sensor unit 100 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention may further include one or more sensors selected from a sound wave sensor, a voltage sensor, and a temperature sensor.

In order to enable the valve diagnosis to be performed in real time even when the valve is in operation, when the data signal out of the set range is acquired, the valve management unit 200 includes a portable controller 400, The alarm signal may be transmitted to the on-site operator or the main control room operator by causing the controller 300 to generate an alarm signal.

In addition to the sensors mentioned above, thrusts, valve stem changes, valve actuator clearances, flow and fluid pressures in the system can be used for changes in valve driving forces (supply or supply), disc trajectory changes, valve movement and stopping Data can be acquired and monitored by using the smart sensor unit 100 composed of sensors for signals, and it is possible to confirm the abnormality (failure) based on the data.

4, the valve management unit 200 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention includes a signal management unit 210 for collecting and storing the sensing signals, And a determination unit 220 for determining whether the valve 10 is normal based on the sensing signal stored in the signal management unit 210 according to the diagnosis algorithm.

The judging unit 220 evaluates the output of the actuator. The actuator output evaluation evaluates the allowance of the force required when the valve is closed or opened. The larger the allowance, the lower the occurrence frequency of hunting. The fault is reduced, and the smaller the allowance, the higher the frequency of occurrence of hunting may occur, resulting in incapacity.

The determination unit 220 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention

Based on the sensing values of the displacement sensor 110, the fluid pressure sensor 120 and the thrust sensor 130 (see FIG. 2)

Actuator output / Seat ring force <1

) * 변형률(%) * 재료 탄성계수(

), 시트링 포스= 시트링 면적 * 밸브 내부 유체 압력)(Where actuator output = actuator stem cross section (

) * Strain (%) * Material elastic modulus (

), Seat ring force = seat ring area * fluid pressure inside valve)

It is determined that the signal is abnormal.

Here, the strain (%) can be measured by the thrust sensor 130, and the fluid pressure can be measured using the fluid pressure sensor 120.

The thrust sensor 130 can be installed by attaching and bonding a strain gauge to the shaft of the actuator stem 21 exposed to the outside of the actuator 20. The data can be zeroed when the valve is closed or opened.

The strain measurement at the time of closing or opening can be measured until there is no strain change after valve operation, and if it is in the range of -0.05% to + 0.05%, it can be determined that there is no deformation (0%) in the actuator stem (21) , The maximum strain can be used as a measurement value.

3) using a positioner pressure sensor 140 for measuring the pressure on the actuator positioner 22 side in the actuator 20 instead of the thrust sensor 130,

) * 구동기 피스톤(다이아프램 루버 면적) 면적(

)Actuator output = Actuator internal working pressure (

) * Actuator piston (Diaphragm louver area) Area (

)

(Here, material elastic modulus is material test value or published data)

.

)은 포지셔너압력센서(140)로 측정할 수 있다.Here, the operating pressure inside the actuator (

Can be measured with the positioner pressure sensor 140. [

The positioner pressure sensor 140 measures the pressure in the cylinder 20 of the actuator 20, measures about 1,000 data per second, calculates an average excluding the largest value and the smallest value, and measures the calculated average value Can be used as a value.

The driver output evaluation can be evaluated and output in four ways in total.

1) Step 1: 0.85 ~ 1: Driver can not be operated and need maintenance

2) Step 2: 1.05 ~ 1.1: Reduction of driver output margin and check

3) Step 3: 1.15 ~ 1.3: Driver output is normal

4) Step 4: 1.35 ~ 1.5: Actuator output transient and valve damage

In addition, the situation judgment and action measures according to the driver output evaluation can also be evaluated and output in total of four.

1) Step 1: Insufficient supply pressure - Maintenance and replacement of regulator, piston o-ring, actuator crack, diaphragm louver

2) Step 2: Insufficient supply pressure - Regulator pressure check, lubricating oil inside driver and piston o-ring check

3) Step 3: Normal operation

4) Step 4: Excessive supply pressure - Check plug and seat ring (Replace when required)

The determination unit 220 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention determines whether a graph of a displacement over time after a valve opening / closing signal is transmitted to the main control unit 300, And if it is out of the predetermined error range, it is determined that the error is abnormal.

When the actuator stem 21 is buckled and deformed due to an excessive output of the actuator 20, the actuator stem 21 in which the buckling has occurred is pinched in the valve bonnet packing portion during the valve operation, Fluid leakage may occur due to poor seating, and a phenomenon in which the valve operation can not be performed may occur due to a phenomenon in which the sealing ring at the lower end of the actuator 20 is inserted.

The determination unit 220 of the multi-channel valve control and self-diagnosis system according to an embodiment of the present invention determines whether the difference between the measured data of the opening rate change and the basic displacement data exceeds 10% And output it.

The determination unit 220 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention determines whether the valve 10 is normal based on the stem vibration generated when the valve is closed .

For example, when the valve is closed, a vibration sensor (including an ultrasonic sensor) may be attached to the actuator stem 21 to acquire vibration or ultrasound data. Based on this, it is possible to determine whether the valve 10 is normal, .

The determination unit 220 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention determines that it is abnormal when the temperature increases or decreases by 40 to 60% or more from the temperature change during operation.

For example, it can be determined that the valve disk is damaged or an abnormality indicating an increase in fluid overflow occurs when the operation temperature is increased or decreased by 50% or more from the normal operation temperature change, and it can be informed by an alarm or the like.

The determination unit 220 of the multi-channel valve control and self-diagnosis system according to an exemplary embodiment of the present invention determines whether abnormality (abnormality) occurs when an electric signal (voltage, current) of a communication module or a signal cable used for communication changes by 20% It is determined that there is an error.

For example, when the electric signal (voltage, current, etc.) of the communication module or the signal cable is increased or decreased by 30% or more than the normal operation electric signal during operation, it can be determined that it is abnormal and can be informed by an alarm or the like.

The portable controller 400 of the multi-channel valve control and self-diagnosis system according to an embodiment of the present invention may obtain access authority for the valve manager 200 from the main controller 300, 200) and controls the valve management unit (200) after acquiring control authority from the main control unit (300) in the valve management unit (200).

Opening and closing control of the valve 10 should not be performed by an unauthorized user. Therefore, it is preferable that a user who has been given a legitimate access right is able to connect to the corresponding valve 10 by using the portable control unit 400. [

For this purpose, when attempting to connect to the specific valve 10 using the portable control unit 400, the control unit 400 must be approved by the main control unit 300 so that the portable control unit 400 can be connected to the specific valve 10 .

At this time, if the field worker inputs information such as information for identifying who is the field operator using the portable control unit 400, work to be connected to the specific valve 10, work time, etc., When the portable control unit 400 transmits the information to the main control unit 300 and the main control unit 300 receiving the information approves the corresponding operation (connection or control), the on-site operator uses the portable control unit 400 It is preferable to be able to connect or control the specific valve 10.

Although the example in which the on-site operator acquires the access authority or the control authority using the portable controller 400 in the field is described above, the present invention is not limited to this example, and all authority (master authority) It is possible to set various rights and grant authorization.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

10: Valve
20:
21: Actuator stem 22: Actuator positioner
30: Connection
100: Smart sensor unit
110: displacement sensor 120: fluid pressure sensor
130: Thrust sensor 140: Positioner pressure sensor
200:
210: signal management unit 220:
300:
400:

Claims (10)

A smart sensor unit 100 provided with a plurality of sensors used for monitoring the state of the valve 10 and the actuator 20;
A valve management unit 200 receiving a sensing signal from the smart sensor unit 100 and activating or deactivating the valve 10 according to a valve opening / closing signal;
A main controller 300 connected to the valve manager 200 to receive the sensing signal and to transmit a valve opening / closing signal for controlling the opening / closing of the valve 10 to the valve manager 200; And
A valve open / close signal for controlling opening and closing of the valve 10 is transmitted to the valve management unit 200, which is connected to the valve management unit 200 by wire or wirelessly, receives the detection signal from the valve management unit 200, A portable controller 400;
/ RTI &gt;
The valve management unit 200
A signal management unit 210 for collecting and storing the sensing signals; And
A determination unit 220 for storing a diagnosis algorithm and determining whether the valve 10 is normal based on a sensing signal stored in the signal management unit 210 according to the diagnosis algorithm;
Channel valve control and self-diagnosis system.
The method according to claim 1,
The smart sensor unit 100 includes:
A displacement sensor 110 installed at a connection portion 30 between the valve 10 and the actuator 20 to measure the position of the actuator stem 21;
A fluid pressure sensor (120) for measuring fluid pressure inside the valve (10); And
A thrust sensor (130) installed on the actuator stem (21) and measuring an axial force;
Channel valve control and self-diagnosis system.
The method according to claim 1,
The valve (10)
A unique identifier is assigned,
The portable controller (400)
Channel control and self-diagnosis system wirelessly identifies the unique identifier of the valve (10) and connects to the valve management unit (200) connected to the valve (10) based on the unique identifier.
delete The method according to claim 1,
The smart sensor unit 100 includes:
Channel sensor, a sound sensor, a voltage sensor, and a temperature sensor.
delete The method according to claim 1,
The determination unit 220 determines
When the graph of the displacement over time after the valve opening / closing signal is transmitted to the main control unit (300) is out of the predetermined error range in the normal operating range, the multi-channel valve control and self- system.
The method according to claim 1,
The determination unit 220 determines
And determines whether the valve (10) is normal or not based on the stem vibration generated when the valve is closed.
The method according to claim 1,
The determination unit 220 determines
And when it is increased or decreased by 40 to 60% or more from the temperature change during operation, it is determined to be abnormal.
The method according to claim 1,
The determination unit 220 determines
Channel voltage of the communication module or signal cable used for communication is abnormal when the electric signal (voltage, current) changes by 20 to 40% or more.

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