JP2008123084A - Transmission line abnormality diagnostic field equipment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field equipment system detecting abnormality of a transmission line by detecting increase of transmission-line current when a terminal part of field equipment is submerged. <P>SOLUTION: This field equipment system with the transmission line has a diagnostic module detecting an abnormality of the transmission line. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a field device system connected to a transmission line, and more particularly to detection and diagnosis of an abnormality such as a short circuit of a transmission line.

  For example, in plant instrumentation, a system in which a host device and a field device are connected by a transmission line may be used. Such a system is exposed to wind and rain when used outdoors, and rainwater or the like may enter the field device, so that the terminal portions may be submerged and the terminal portions may be short-circuited.

  FIG. 11 shows a configuration of a conventional general field device system 12. The transmission lines 1 and 2 are connected to a common DC power source 3. The standard of the field device system 12 includes a foundation field bus, FOFIBUS, and HART.

  A pair of terminators 4 and 5 are connected to both ends of the transmission lines 1 and 2, and a host device 6 that performs communication via the transmission line is connected to the transmission lines 1 and 2.

  Further, a differential pressure transmitter 9 which is one of field devices is connected to the transmission lines 7 and 8 branched from the transmission lines 1 and 2. Similarly, a temperature transmitter 10 and a vortex flowmeter 11 which are field devices are connected to a transmission line branched from the transmission lines 1 and 2. Other field devices include electromagnetic flow meters, Coriolis mass flow meters, ultrasonic flow meters, and level meters.

  The transmission lines 7 and 8 are connected to independent terminal portions (not shown) inside the field device through a wiring port (not shown) of a field device such as the differential pressure transmitter 9. A packing is provided at the wiring port so that rainwater or the like does not enter the field device through the wiring port.

  In such a connection configuration, one of a plurality of field devices such as the differential pressure transmitter 9 is selected at a command from the host device 6 or at a constant cycle, and the host device 6 is subjected to AC modulation of the current consumption of the selected field device. Communication is performed with

  On the other hand, a field device such as the differential pressure transmitter 9 converts a physical quantity such as differential pressure / pressure or flow rate into an electrical signal by a sensor, and calculates a differential pressure / pressure value, a flow rate value, and the like. The calculated value is converted into the AC modulation signal and transmitted to the host device 6, and the host device 6 controls the physical quantity.

  This current consumption is designed to be, for example, 4-20 mA, and the span of the variable portion 0-16 mA is AC-modulated by ± 8 mA with 8 mA as the center. When the load resistance between the transmission lines 1 and 2 is designed to be 50Ω, an AC voltage of ± 400 mV is generated between the transmission lines 1 and 2 and the host device 6 receives this. The communication signal is superimposed on the voltage between the transmission lines 1 and 2 by a FOUNDATION FIELDBUS signal of 0.75 to 1 Vp-p.

  Note that FIG. 2 of Patent Document 1 outlines the configuration of such a conventional general field device system.

  Further, FIG. 12 shows a configuration of a conventional general field device system 19. 12, the same components as those in FIG. 11 are denoted by the same reference numerals, and description thereof is omitted.

  Field devices such as the differential pressure transmitter 9 are connected to the transmission lines 1 and 2 via the transmission lines 7 and 8, the plural device connection device 15, and the transmission lines 13 and 14.

  Specifically, the multiple device connection device 15 is connected to the transmission lines 13 and 14 branched from the transmission lines 1 and 2. One of the connection terminals 16 of the multiple device connection device 15 is connected to the transmission lines 13 and 14, and the other is connected to the transmission lines 7 and 8. A differential pressure transmitter 9 is connected to the transmission lines 7 and 8. Similarly, the connection terminals 17 and 18 are also connected to the temperature transmitter 10 and the vortex flowmeter 11 through transmission lines.

  In such a connection configuration, the host device 6 communicates with a plurality of field devices such as the differential pressure transmitter 9 to control physical quantities.

JP 2004-86405 A

  However, in FIG. 11 and FIG. 12, if the packing of the wiring port is not properly provided, rainwater or the like may enter the field device and the terminal portion may be submerged.

When the terminal part is submerged, water is electrolyzed by a voltage applied to the terminal part, and dangerous gas such as hydrogen may be generated from the terminal part. Moreover, the metal of a terminal part ionizes and elutes in water by electrolysis, the electrical conductivity in water rises, and a leakage current may flow between independent terminal parts. If the leakage current further increases, the terminals may be short-circuited.

Due to the increase in leakage current, the transmission line current flowing in the transmission lines 1, 2, 7, and 8 increases and the output voltage of the DC power supply 3 decreases, causing an abnormality in the transmission lines 1, 2, 7, and 8, and the host device. A communication failure that prevents communication between 6 and a plurality of field devices occurs.

  On the other hand, in FIG. 12, the leakage current increases in the same way, but the output voltage of the DC power supply 3 is lowered because the transmission line current flowing in the transmission lines 7 and 8 is limited by the current limiting function of the multiple device connecting device 15. Therefore, it is possible to prevent a communication failure from occurring.

  However, depending on the component of rainwater and the submerged condition, the leakage current repeatedly increases and decreases below the current limit value of the multi-device connection device 15, and noise occurs in the transmission lines 1, 2, 13, 14, 7, and 8. A superimposing abnormality occurs, and a communication failure that prevents communication between the host device 6 and a plurality of field devices occurs.

  An object of the present invention is to detect an increase in transmission line current due to an increase in leakage current flowing between terminal parts when the terminal part of a field device is submerged, and to reduce the output voltage of a DC power source or transmission line due to noise superposition It is an object of the present invention to provide a field device system including a diagnostic module for detecting abnormalities in the apparatus.

In order to achieve such an object, the invention of claim 1
In a field device system including a transmission line,
With a diagnostic module that detects the presence or absence of an abnormality in the transmission line,
It is characterized by that.

The invention of claim 2 is the invention of claim 1,
The diagnostic module includes:
A current measurement unit for measuring the transmission line current;
A threshold value calculation unit that calculates a threshold value based on an initial measurement value of the current measurement unit;
A comparison unit that compares the measured value of the current measurement unit and the threshold;
With an alarm output unit that outputs an alarm based on the output of the comparison unit,
It is characterized by that.

The invention of claim 3 is the invention of claim 2,
The diagnostic module includes:
In addition, it has a communication unit that communicates information.
It is characterized by that.

The invention of claim 4 is the invention according to claim 2 or 3,
The diagnostic module includes:
Furthermore, a storage unit for storing the measurement value of the current measurement unit together with time information is provided.
It is characterized by that.

The invention according to claim 5 is the invention according to any one of claims 2 to 4,
The diagnostic module includes:
Connected to the transmission line to which the field device is connected,
It is characterized by that.

The invention of claim 6 is the invention of claim 5,
An opening / closing part for connecting or disconnecting the transmission line based on an alarm output of the diagnostic module,
It is characterized by that.

  According to the present invention, when a terminal portion of a field device is submerged, an increase in the transmission line current due to an increase in leakage current flowing between the terminal portions is detected, and a transmission line due to a decrease in the output voltage of the DC power supply or superimposition of noise is detected. It is possible to realize a field device system including a diagnostic module for detecting abnormalities in the apparatus.

[First embodiment]
A first embodiment will be described with reference to FIGS. FIG. 1 shows a field device system according to the first embodiment of the present invention. The same components as those in FIG. FIG. 2 shows a field device system when the multiple device connecting device 15 is used in FIG. 1, and the same components as those in FIG. 1 and FIG. FIG. 3 is a block diagram of the diagnostic module 20.

Hereinafter, description will be made assuming that the terminal portion of the differential pressure transmitter 9 is submerged.
The diagnostic module 20 is connected to transmission lines 1, 21 and 2 connected between the DC power supply 3 and the plurality of field devices in order to measure transmission line currents flowing through the plurality of field devices such as the differential pressure transmitter 9. To do.

  Specifically, the terminal A of the diagnostic module 20 is connected to the transmission line 1, the terminal B is connected to the transmission line 21, and the terminal C is connected to the transmission line 2. A terminator 5 is connected to the transmission lines 21 and 2, and a differential pressure transmitter 9 which is one of field devices is connected to the transmission lines 7 and 8 branched from the transmission lines 21 and 2. Similarly, a temperature transmitter 10 and a vortex flowmeter 11 which are field devices are connected to a transmission line branched from the transmission lines 21 and 2.

  The diagnostic module 20 includes a power generation unit 24, a current measurement unit 25, a threshold value calculation unit 26, a comparison unit 27, an alarm output unit 28, and a control unit 29.

  The power supply generation unit 24 is connected to the terminals A and C, generates an internal power supply voltage 30 from the output voltage of the DC power supply 3, and supplies it to each unit such as the current measurement unit 25.

  The current measuring unit 25 is connected to the terminals A and B, and measures the currents of the transmission lines 1, 21, and 2 flowing through a plurality of field devices such as the differential pressure transmitter 9.

  The threshold calculation unit 26 calculates a threshold 32 based on the initial measurement value 31 of the current measurement unit 25. The comparison unit 27 compares the threshold value 32 with the measurement value 33 of the current measurement unit 25. The alarm output unit 28 outputs an alarm based on the output of the comparison unit 27. The output of the alarm output unit 28 is connected to an acoustic device such as a buzzer or a lamp or a lighting device (not shown).

  The operation of the diagnostic module 20 will be described with reference to the flowchart of FIG.

  By outputting the voltage of the DC power supply 3, a voltage is applied to the terminals A and C of the diagnostic module 20 (step S1), and steps S2 and after are executed.

  The measurement value of the current measurement unit 25 is input to the threshold value calculation unit 26 as the initial measurement value 31 (step S2). The initial measurement value 31 is a current of the transmission lines 1, 21, 2 flowing in a plurality of field devices such as the differential pressure transmitter 9 when the transmission line is normal.

  The threshold value calculation unit 26 detects an abnormality in the transmission line by adding, to the initial measurement value 31, the variation in the current of the transmission lines 1, 21, and 2 flowing in the field device such as the differential pressure transmitter 9 when normal. The threshold value 32 is calculated (step S3). The threshold value 32 is input to the comparison unit 27. Since the threshold value 32 varies depending on the current variation of the field devices such as the differential pressure transmitter 9 and the structure of the terminal portions thereof, the threshold value 32 may be changed and set.

  Next, abnormality diagnosis of the transmission line is started (step S4). The measurement value 33 (step S5) of the current measurement unit 25 is input to the comparison unit 27. The comparison unit 27 compares the measured value 33 with the threshold value 32 (step S6). If the measured value 33 is larger than the threshold value 32, the diagnostic module 20 detects that there is an abnormality in the transmission line (step S7).

  The alarm output unit 28 outputs an alarm signal for generating sound from an acoustic device such as a buzzer or lighting or blinking a lighting device such as a lamp in order to notify that there is an abnormality in the transmission line (step S8). ).

  If the measured value 33 is smaller than the threshold value 32, the diagnostic module 20 detects that there is no abnormality in the transmission line (step S9) and does not output the alarm signal. Henceforth, the process after step S4 is repeated.

  The control unit 29 controls and executes processing based on each unit such as the comparison unit 27 and the flowchart of FIG. The control unit 29 can be realized by a microprocessor unit (MPU) including the comparison unit 27 and the like.

  Further, FIG. 10 shows an example of a change with respect to time of the currents of the transmission lines 7 and 8 flowing in the differential pressure transmitter 9 when the terminal portion of the differential pressure transmitter 9 is submerged. Cur1 indicates a current flowing through the differential pressure transmitter 9 when the transmission line is normal (about 15 mA). Cur2 indicates a leakage current that flows between the terminal portions when the terminal portions are submerged.

  When the terminal part of the differential pressure transmitter 9 is submerged, the leakage current Cur2 takes about several hours to about one day and becomes about 30 mA (T1). After that, when the corrosion of the terminal portion starts, it takes about several days and the leakage current Cur2 stops flowing (T2). If the measured value is larger than the threshold value, an alarm is output, and if it is smaller, no alarm is output.

  According to this embodiment, when the terminal part of the field device is submerged, the diagnostic module 20 detects an increase in the transmission line current due to an increase in leakage current flowing between the terminal parts, and reduces the output voltage of the DC power supply or noise. Detects transmission line anomalies due to superposition. Then, by outputting an alarm, it is notified that there is an abnormality and prompts the user to remove or replace the field device that is causing the abnormality. As a result, it is possible to realize a field device system with improved reliability that can prevent the occurrence of communication failure, prevent the generation of dangerous gas such as hydrogen, and continue to control the physical quantity.

[Second Embodiment]
A second embodiment of the block diagram of the diagnostic module 20 will be described with reference to FIG. In FIG. 4, the same components as those in FIG.

  In FIG. 4, the communication unit 34 is connected to the terminal A, the terminal C, and the control unit 29. The communication unit 34 receives a communication signal requesting information held by the diagnostic module 20 from the host device 6 via the transmission lines 1 and 2, and transmits the information to the host device 6 via the control unit 29. The information includes the output of the alarm output unit 28, the measured value 33 of the current measuring unit 25, and the like. For example, as an alarm output, data “1” is transmitted as information when there is an abnormality in the transmission line (step S7), and data “0” is transmitted as information when there is no abnormality (step S9). The communication unit 34 may also perform the operation of the control unit 29 and may acquire information between the output of the alarm output unit 28 and the output of the current measurement unit 25 without going through the control unit 29.

  According to the present embodiment, in the control room where the host device 6 is installed, the presence or absence of the transmission line can be intensively monitored through the host device 6, so that the field device causing the abnormality can be quickly removed. In addition, it is possible to replace them, to prevent occurrence of communication failure, to prevent generation of dangerous gas such as hydrogen, and to realize a field device system with improved reliability capable of continuing control of physical quantities.

[Third embodiment]
A third embodiment of the block diagram of the diagnostic module 20 will be described with reference to FIG. In FIG. 5, the same components as those in FIGS.

  In FIG. 5, the diagnostic module 20 includes a time timer 35 and a storage unit 36. The time timer 35 has time information including the current date and time. The storage unit 36 is connected to the output of the current measurement unit 25, the output of the time timer 35, and the control unit 29.

  The storage unit 36 stores the measurement value 33 of the current measurement unit 25 as well as the time information of the timer 35 as information of the diagnostic module 20. For example, storage in the storage unit is executed between steps S5 and S6 in FIG. Alarm output data may be stored in the storage unit 36 via the control unit 29 in steps S7 and S9.

  In response to a signal requesting information from the host device 6, the communication unit 34 transmits the time information, the measured value 33, and alarm output data to the host device 6 from the storage unit 36 via the control unit 29. The communication unit 34 may also perform the operation of the control unit 29, and may acquire the information with the output of the storage unit 36 without passing through the control unit 29.

  According to the present embodiment, the measured value 33 can be monitored in time series, and the field device that may cause the abnormality is removed before the measured value 33 gradually increases and an alarm output is given to notify that there is an abnormality in the transmission line. Therefore, it is possible to prevent the occurrence of communication failures and the generation of dangerous gases such as hydrogen, and it is possible to realize a field device system with improved reliability capable of continuing control of physical quantities.

[Fourth embodiment]

  A fourth embodiment in which the connection location between the diagnostic module 20 and the transmission line is different from that in FIGS. 1 and 2 will be described with reference to FIGS. 6 and 7. FIG. 6 is a field device system showing an embodiment in which the diagnostic module 20 is connected to the transmission lines 7 and 8. FIG. 7 shows a field device system when the multiple device connecting device 15 is used in FIG. 6, and the same components as those in FIG. 1 and FIG.

  Specifically, the terminal A of the diagnostic module 20 is connected to the transmission line 7, the terminal B is connected to the transmission line 37, and the terminal C is connected to the transmission line 8.

  In the first to third embodiments, the diagnostic module 20 measures the transmission line current flowing in a plurality of field devices such as the differential pressure transmitter 9, whereas in this embodiment, one differential pressure transmission is performed. The transmission line current flowing in the field device such as the device 9 is measured. Therefore, the threshold value calculation unit 26 calculates or sets a threshold value 32 for detecting an abnormality in the transmission lines 7, 37, and 8 due to a leakage current flowing between the terminal portions of one field device.

  According to the present embodiment, when the alarm output unit 28 outputs an alarm output having an abnormality in the transmission line, the field device causing the abnormality can be identified, and the field device can be removed or replaced more quickly. Therefore, it is possible to prevent the occurrence of communication failure, prevent the generation of dangerous gas such as hydrogen, and realize a highly reliable field device system capable of continuing the control of the physical quantity.

[Fifth embodiment]
A fifth embodiment in which an opening / closing part 43 is further provided with respect to FIG. 7 will be described with reference to FIG. The open / close section 43 is connected between the transmission lines 37 and 8 and field devices such as the differential pressure transmitter 9.

  Specifically, the terminal A of the diagnostic module 20 is connected to the transmission line 7, the terminal B is connected to the transmission line 37, and the terminal C is connected to the transmission line 8. The opening / closing unit 43 is connected to the transmission lines 37 and 8 and the output of the alarm output unit 28 of the diagnostic module 20, and is connected to the differential pressure transmitter 9 via the transmission lines 41 and 42.

  In step S <b> 9 of FIG. 9, the opening / closing unit 43 connects the transmission lines 37, 8 and 41, 42 based on an alarm output that is not abnormal in the transmission line of the alarm output unit 28. In step S7, the opening / closing unit 43 cuts the transmission lines 37, 8 and 41, 42 based on an alarm output having an abnormality in the transmission line. After that, the alarm output unit 28 maintains an abnormal output, and the switching unit 43 maintains the state in which the transmission lines 37, 8 and 41, 42 are disconnected based on the output. The open / close unit 43 may be connected in series between the current measuring unit 25 and B of the diagnostic module 20. Further, similarly to FIG. 6, an embodiment provided with an opening / closing part 43 is also possible.

  According to this embodiment, when the alarm output unit 28 outputs an alarm output having an abnormality in the transmission line, the field device causing the abnormality is automatically disconnected from the connected transmission line. Therefore, it is possible to prevent the occurrence of communication failure more quickly, prevent the generation of dangerous gas such as hydrogen, and realize a highly reliable field device system capable of continuing the control of the physical quantity.

  It should be noted that the present invention is not limited to submersion of the terminal portion of the field device, but also against abnormalities in the transmission line such as submergence caused by rainwater or the like of the connection terminals 16, 17 and 18 of the multi-device connection device 15 or short circuit due to deterioration of the transmission line. Even applicable. Further, the diagnostic module 20 may be provided inside the multiple device connecting device 15.

It is a block diagram which shows one Example of this invention. It is a block diagram which shows the other Example of this invention. 3 is a block diagram illustrating a specific example of a diagnostic module 20. FIG. It is a block diagram which shows the other specific example of the diagnostic module 20. FIG. It is a block diagram which shows the other specific example of the diagnostic module 20. FIG. It is a block diagram which shows the other Example of this invention. It is a block diagram which shows the other Example of this invention. It is a block diagram which shows the other Example of this invention. 4 is a flowchart showing the operation of the diagnostic module 20. It is an example of the characteristic with respect to time of the transmission line current when the terminal part of a differential pressure transmitter is submerged. It is a block diagram which shows an example of the past. It is a block diagram which shows the other example of the past.

Explanation of symbols

2, 7, 8, 13, 14, 21 Transmission line 3 DC power supply terminator 6 Host device 9 Differential pressure transmitter 10 Temperature transmitter 11 Vortex flow meter 15 Multiple device connection device 20 Diagnostic module 22, 23 Field device system 24 Power generation Unit 25 Current measurement unit 26 Threshold calculation unit 27 Comparison unit 28 Alarm output unit 29 Control unit 30 Internal power supply 31 Initial measurement value 32 Threshold value 33 Measurement value 34 Communication unit 35 Time timer 36 Storage unit

Claims (6)

In a field device system including a transmission line,
With a diagnostic module that detects the presence or absence of an abnormality in the transmission line,
A field device system characterized by that. The diagnostic module includes:
A current measurement unit for measuring the transmission line current;
A threshold value calculation unit that calculates a threshold value based on an initial measurement value of the current measurement unit;
A comparison unit that compares the measured value of the current measurement unit and the threshold;
With an alarm output unit that outputs an alarm based on the output of the comparison unit,
The field device system according to claim 1. The diagnostic module includes:
In addition, it has a communication unit that communicates information.
The field device system according to claim 2, wherein: The diagnostic module includes:
Furthermore, a storage unit for storing the measurement value of the current measurement unit together with time information is provided.
The field device system according to claim 2, wherein the field device system is a field device system. The diagnostic module includes:
Connected to the transmission line to which the field device is connected,
The field device system according to claim 2, wherein the field device system is a field device system. An opening / closing part for connecting or disconnecting the transmission line based on an alarm output of the diagnostic module,
The field device system according to claim 5, wherein:

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