Surveillance system and method

Abstract

To enable time synchronization of sampling by each of a plurality of analog input (AI) circuits installed at mutually distant positions.SOLUTION: A monitoring system 10 includes a plurality of expansion input units 110 (A, B, C) and a control unit 100. The control unit 100 transmits first and second sampling instructions to first and second expansion units 110, respectively, of the plurality of expansion units. The first sampling instruction includes information about a first wait time based on a first transmission delay time. The second sampling instruction includes information about a second wait time based on a second transmission delay time. Each of the first and second expansion units 110 initiates a sampling process after a specified wait time has elapsed from reception of the sampling instruction and transmits a result of the sampling process to the control unit 100.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to equipment monitoring systems, and more particularly, to synchronizing sampling in monitoring systems. [Background technology]

[0002] Protection devices (protective relay devices, etc.) are sometimes used to protect substation facilities and the like. The protection devices can control switches and the like based on sampled data of monitored items such as voltage or current acquired from an analog input (AI (Analog Input)) circuit. In recent years, protection devices and multiple AI circuits are sometimes installed at locations distant from each other and configured to communicate via optical fiber or the like. In this case, differences in transmission delay times between each AI circuit and the protection devices can cause discrepancies in the sampling times of the sampled data acquired by the protection devices. For this reason, a method for synchronizing sampling is needed.

[0003] Concerning a sampling synchronization method, for example, Publication No. 254619 / 1987 (Patent Document 1) discloses a sampling time synchronization method that "synchronizes the operation sampling times of a host device and a subordinate device connected via a transmission line, by setting delay time information of the transmission line in advance in the synchronization circuit section of the subordinate device, and delaying the startup of the synchronization signal of the subordinate device by the delay time, thereby almost eliminating the pull-in time of the synchronization signal from the host device and enabling instantaneous sampling time synchronization" (see [Summary]). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Publication number 62-254619 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technology disclosed in Patent Document 1, it is not possible to synchronize the sampling times of multiple AI circuits installed at distant locations. Therefore, there is a need for a technology that enables the sampling times of multiple AI circuits installed at distant locations to be synchronized.

[0006] The present disclosure has been made in consideration of the above-described background, and an object of one aspect is to enable time synchronization of sampling by each of multiple AI circuits installed at locations remote from each other. [Means for solving the problem]

[0007] According to one embodiment, a monitoring system is provided. The monitoring system includes a plurality of expansion units for sampling monitoring items of equipment, and a control unit connected to each of the plurality of expansion units via a transmission line and for monitoring the equipment. The control unit transmits a first sampling instruction to a first expansion unit among the plurality of expansion units, and transmits a second sampling instruction to a second expansion unit among the plurality of expansion units. At the same time as the first sampling instruction is sent A second sampling instruction is transmitted. The first sampling instruction includes information of a first waiting time based on a first transmission delay time between the control unit and the first extension unit. The second sampling instruction includes information of a second waiting time based on a second transmission delay time between the control unit and the second extension unit. The first extension unit starts a sampling process after the first waiting time has elapsed since receiving the first sampling instruction, and transmits the first sampling result to the control unit. The second extension unit starts a sampling process after the second waiting time has elapsed since receiving the second sampling instruction, At the same time as the first sampling process begins The sampling process is started and the second sampling result is sent to the control unit. Effect of the Invention

[0008] According to one embodiment, it is possible to enable time synchronization of sampling by each of a plurality of AI circuits installed at locations remote from each other.

[0009] The above and other objects, features, aspects and advantages of this disclosure will become apparent from the following detailed description of the disclosure, which is to be understood in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0010] [Figure 1] It is a diagram showing an example of the configuration of a monitoring system 10 according to an embodiment. [Diagram 2] It is a diagram showing an example of the configuration of an AI sampling instruction frame 210 and an AI data frame 220. [Diagram 3] It is a diagram showing an example of the configuration of a waiting time table 300. [Figure 4] It is a diagram showing an example of a communication sequence in the monitoring system 10. [Diagram 5] It is a diagram showing an example of the hardware configuration of an extended unit communication circuit 105 and a communication circuit 111. [Figure 6] It is a diagram showing a first example of the components of the delay time generated when transmitting and receiving a measurement frame 550. [Figure 7] It is a diagram showing an example of the communication flow when the cut-through path 518 is not used. [Figure 8] It is a diagram showing a second example of the components of the delay time generated when transmitting and receiving a measurement frame 550.

Modes for Carrying Out the Invention

[0011] Hereinafter, embodiments of the technical idea according to the present disclosure will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated. In the following description, when referring to a plurality of identical configurations, they may be expressed as configuration 123A, 123B, etc. Also, when collectively referring to them, they are expressed as configuration 123. <A. System Configuration> 1 is a diagram showing an example of the configuration of a monitoring system 10 according to the present embodiment. The monitoring system 10 monitors equipment in any facility including, for example, a substation or a power plant. The equipment to be monitored may include a power transmission line. Furthermore, when the monitoring system 10 detects, for example, an abnormal current or voltage in the equipment to be monitored, it may control a switch or the like to stop the power transmission.

[0012] (a. Hardware Configuration) The monitoring system 10 includes a control unit 100, a plurality of extension input units 110, and a current / voltage sensor 130. The control unit 100 includes a CPU (Central Processing Unit) 101, a memory 102, a network I / F (Interface) circuit 103, a clock circuit 104, an extension unit communication circuit 105, a DIO (Digital Input Output) circuit 106, and an AI circuit 107. The extension input unit 110 includes a communication circuit 111 and an AI circuit 112. The current / voltage sensor 130 is a current sensor or a voltage sensor. Each of the plurality of extension input units 110 is connected to the extension unit communication circuit 105 via a transmission path 120. In one aspect, the transmission path 120 may be an optical fiber. In another aspect, the transmission path 120 may be realized by any wired circuit or wireless device.

[0013] The control unit 100 has a function as a protective relay device, and can monitor multiple pieces of equipment by linking with the expansion input unit 110. The control unit 100 has a function of monitoring equipment on its own, and a function of monitoring equipment in linkage with the expansion input unit 110. Each function will be described below.

[0014] (b. Monitoring function of the control unit alone) First, the function of monitoring equipment by the control unit 100 alone will be described. The AI ​​circuit 107 is connected to one or more current / voltage sensors 130 and acquires sampling data of current or voltage. The DIO circuit 106 is connected to, for example, a switch and outputs a signal for switching the switch on / off.

[0015] The CPU 101 acquires sampling data from the AI ​​circuit 107. The CPU 101 may also refer to the sampling data to determine whether or not there is an abnormality in the current or voltage of the monitored object. Furthermore, the CPU 101 switches the output of the DIO circuit 106 to control the switch based on the determination that there is an abnormality in the current or voltage of the monitored object. In this way, when an abnormality occurs in the equipment to be monitored, the CPU 101 may control the switch to stop power transmission.

[0016] (c. Cooperation Function of Control Unit and Expansion Input Unit 110) Next, a function of monitoring the equipment in cooperation with the expansion input unit 110 in the control unit 100 will be described. The expansion unit communication circuit 105 communicates with one or more expansion input units 110. The expansion unit communication circuit 105 may include multiple communication ports to communicate with multiple expansion input units 110.

[0017] The AI ​​circuit 112 in the expansion input unit 110 is connected to one or more current / voltage sensors 130 and acquires sampling data of current or voltage. The communication circuit 111 transmits the sampling data acquired by the AI ​​circuit 112 to the expansion unit communication circuit 105. The expansion unit communication circuit 105 transmits the sampling data received from each expansion input unit 110 to the CPU 101 via the internal bus. In other words, the expansion input unit 110 is an AI circuit that can be installed in a location away from the control unit 100.

[0018] The CPU 101 may refer to the sampling data acquired from each expansion input unit 110 to determine whether or not there is an abnormality in the current or voltage of the monitored object. Furthermore, the CPU 101 switches the output of the DIO circuit 106 to control the switch based on the determination that there is an abnormality in the current or voltage of the monitored object. In one aspect, the control unit 100 may include multiple DIO circuits 106. In that case, each DIO circuit 106 may control the power transmission of the equipment from which each expansion input unit 110 samples the current or voltage.

[0019] In either function, the memory 102 may store data such as thresholds necessary for abnormality determination, and programs executed by the CPU 101. The CPU 101 refers to the memory 102 to acquire necessary programs and data as appropriate. The network I / F circuit 103 is connected to a local area network or a wide area network. The CPU 101 may notify an external device of an alert via the network I / F circuit 103 based on the detection of an abnormality in the monitored object. The clock circuit 104 generates a timestamp. The timestamp may be used for a sampling synchronization function and a transmission delay time measurement function, which will be described later.

[0020] (d. Overview of Sampling Synchronization Function) Next, an overview of the sampling synchronization function of the monitoring system 10 will be described. As described above, the control unit 100 and the multiple extension input units 110 can be installed at positions distant from each other. This allows the control unit 100 to monitor a wide range of equipment. However, a difference in transmission distance between the control unit 100 and each extension input unit 110 can cause a difference in transmission delay time. For example, a first transmission delay time between the control unit 100 and the extension input unit 110A may be different from a second transmission delay time between the control unit 100 and the extension input unit 110B.

[0021] The sampling timing of the AI ​​circuit 112 is transmitted from the control unit 100 to each expansion unit 110, but if the transmission delay time between the control unit 100 and each expansion input unit 110 is different, the sampling timing of each expansion input unit 110 will differ. If the sampling timing differs, the monitoring program on the control unit 100 may not operate normally. Therefore, the monitoring system 10 has a function for synchronizing the sampling timing of each expansion input unit 110 to suppress the effects of the transmission delay time.

[0022] The sampling synchronization function of the monitoring system 10 synchronizes the sampling timing in the multiple extension input units 110. For example, the control unit 100 transmits a "sampling instruction frame" to each of the extension input units 110A, 110B, and 110C. The sampling instruction frame includes "waiting time information" for the destination extension input unit 110. Note that, hereinafter, all communication data in this embodiment will be referred to as frames, but the communication data in this embodiment may be realized in any format. In a certain aspect, the communication data in this embodiment may be realized by any packet or signal, not just a frame.

[0023] Each of the extension input units 110A, 110B, and 110C starts sampling after the time specified by the wait time information included in the received sampling instruction frame has elapsed. The time specified by the wait time information is determined based on the transmission delay time (which depends on the laying length of the transmission line 120) between the control unit 100 and each of the extension input units 110. The sampling timing of each of the extension input units 110A, 110B, and 110C is synchronized by a sampling synchronization function using the wait time. Details of the sampling instruction frame and more detailed procedures such as generation of a time stamp for sampling data will be described with reference to FIGS. 2 to 4.

[0024] (e. Overview of transmission delay time measurement function) Next, the outline of the measurement function of the transmission delay time of the monitoring system 10 will be described. The control unit 100 measures the transmission delay time between the control unit 100 and each extended input unit 110 in order to determine the waiting time of each extended input unit 110.

[0025] The control unit 100 transmits a measurement frame to each extended input unit 110. The control unit 100 receives the response frame returned from each extended input unit 110. In a certain situation, each extended input unit 110 may transmit the measurement frame as a response frame to the control unit 100. In other situations, each extended input unit 110 may generate a response frame for the measurement frame and transmit the response frame to the control unit 100.

[0026] When the extended input unit 110 receives a normal frame, it temporarily stores the frame in a reception memory (buffer) (not shown). Further, when the extended input unit 110 transmits a frame, it temporarily stores the frame in a transmission memory (buffer) (not shown).

[0027] However, when the extended input unit 110 receives a measurement frame, instead of passing through the reception memory and the transmission memory, it retransmits the measurement frame via a cut-through path (not shown). Since the measurement frame does not pass through the transmission memory and the reception memory that are easily affected by other frames, the delay in processing the measurement frame (from reception to transmission) within the extended input unit 110 is almost a fixed time. Therefore, the control unit 100 can calculate a highly accurate transmission delay time by subtracting the processing time of the measurement frame within the extended input unit 110 from the round-trip time of the measurement frame. For a more detailed procedure regarding the measurement of the transmission delay time, refer to FIGS. 5 to 8 for description.

[0028] <B. Sampling Synchronization Function> Next, a sampling synchronization function of the monitoring system 10 will be described with reference to Fig. 2 to Fig. 4. The sampling synchronization function here refers to synchronizing the sampling start times of the extension input units 110.

[0029] 2 is a diagram showing an example of the configuration of the AI ​​sampling instruction frame 210 and the AI ​​data frame 220. The configuration of the AI ​​sampling instruction frame 210 and the AI ​​data frame 220 will be described with reference to FIG.

[0030] The AI ​​sampling instruction frame 210 includes a command to the expansion input unit 110 to execute sampling, and is transmitted from the control unit 100 to the expansion input unit 110. The AI ​​sampling instruction frame 210 includes a flag 211, a command 212, a sequence number 213, a wait time 214, and a frame check sequence (FCS) 215.

[0031] The flag 211 is a control code indicating the beginning of a frame. For example, this is the K code in 8B10B coding. The command 212 is a sampling instruction for the extended input unit 110. The sequence number 213 is a serial number assigned to the frame. The sequence number 213 can be used to determine the correct sequence of the frames and to detect whether or not a frame is missing.

[0032] The wait time 214 indicates the wait time of the destination expansion input unit 110. Upon receiving the AI ​​sampling instruction frame 210, the expansion input unit 110 starts sampling when the time specified by the wait time 214 has elapsed since receiving the AI ​​sampling instruction frame 210. The FCS 215 is a code for error detection. The FCS 215 is used to detect whether or not an error has occurred in the AI ​​sampling instruction frame 210 during communication.

[0033] The AI ​​data frame 220 contains AI data (sampling data) acquired by the expansion input unit 110, and is transmitted from the expansion input unit 110 to the control unit 100. The AI ​​data frame 220 contains a flag 221, a command 222, a sequence number 223, AI data 224, and an FCS 225.

[0034] The flag 221 is a control code indicating the beginning of a frame. For example, this is the K code in 8B10B coding. The command 222 is an instruction to transmit or receive AI data. The sequence number 223 is a serial number assigned to the frame. The sequence number 223 can be used to determine the correct sequence of frames and to detect whether or not a frame is missing.

[0035] The AI ​​data 224 includes AI data acquired by the expansion input unit 110. In one aspect, when multiple current / voltage sensors 130 are connected to the expansion input unit 110, the AI ​​data 224 may include AI data acquired from each of the current / voltage sensors 130. The FCS 225 is a code for error detection. The FCS 225 is used to detect whether or not an error has occurred in the AI ​​data frame 220 during communication.

[0036] 3 is a diagram showing an example of the configuration of a latency table 300. The control unit 100 determines the value of the latency 214 by referring to the latency table 300. The latency table 300 is stored in the memory 102. In a certain aspect, the latency table 300 may be expressed as a table of a relational database, or may be expressed in any other data format such as JSON (JavaScript (registered trademark) Object Notation). The latency table 300 includes a unit number 301, a transmission delay time 302, and a latency 303.

[0037] The unit number 301 includes an identifier of each expansion input unit 110. As an example, the identifier of expansion input unit 110A is 1, the identifier of expansion input unit 110B is 2, and the identifier of expansion input unit 110C is 3.

[0038] The transmission delay time 302 includes the transmission delay time between the control unit 100 and each expansion input unit 110. For example, the transmission delay time between the control unit 100 and the expansion input unit 110A is 1.5 μ (micro) seconds. In one aspect, the unit of the transmission delay time may be any unit such as m (milli) seconds, μ seconds, or n (nano) seconds.

[0039] Waiting time 303 is the waiting time until sampling starts in each expansion input unit 110. For example, the expansion input unit 110A starts sampling 3.5 μsec after receiving the AI ​​sampling instruction frame 210.

[0040] The control unit 100 determines the waiting time for the extended input units 110 so that all the extended input units 110 start sampling simultaneously after a predetermined "fixed time" has elapsed from the timing of transmission of the AI ​​sampling instruction frame 210.

[0041] The waiting time of each extension input unit 110 is calculated by subtracting the transmission delay time of each extension input unit 110 from the fixed time. For example, assume that the fixed time is 5 μsec. The transmission delay time between the control unit 100 and the extension input unit 110A is 1.5 μsec. In this case, the waiting time of the extension input unit 110A is 3.5 μsec (=5 μsec-1.5 μsec).

[0042] The extension input unit 110A receives the AI ​​sampling instruction frame 210 1.5 μsec after the timing of transmission of the AI ​​sampling instruction frame 210. The extension input unit 110A then delays the execution of sampling by a waiting time of "3.5 μsec" from the time of reception of the AI ​​sampling instruction frame 210. In this way, the extension input unit 110A can start sampling a predetermined fixed time (in this case, the fixed time is 5 μsec) after the timing of transmission of the AI ​​sampling instruction frame 210. The other extension input units 110 operate in a similar manner.

[0043] Fig. 4 is a diagram showing an example of a communication sequence in the monitoring system 10. A detailed procedure of the sampling synchronization function will be described with reference to Fig. 4. In the example shown in Fig. 4, the control unit 100 communicates with each of the extension input units 110A, 110B, and 110C in the same procedure.

[0044] In step S410, the control unit 100 transmits the AI ​​sampling instruction frame 210 to each of the extension input units 110A, 110B, and 110C. More specifically, the control unit 100 refers to the latency table 300 in the memory 102 to acquire the value of the latency 303 of each extension input unit 110. Then, the control unit 100 sets the value of the latency 303 corresponding to the destination to the latency 214. For example, if the destination of the AI ​​sampling instruction frame 210 is the extension input unit 110A, the value of the latency 214 is 3.5 μsec. Also, if the destination of the AI ​​sampling instruction frame 210 is the extension input unit 110B, the value of the latency 214 is 4.0 μsec.

[0045] In step S420, each extension input unit 110 receives the AI ​​sampling instruction frame 210. The timing at which each extension input unit 110 receives the AI ​​sampling instruction frame 210 depends on the length of the transmission path 120 between the control unit 100 and each extension input unit 110. For example, the extension input unit 110A receives the AI ​​sampling instruction frame 210 1.5 μsec after the control unit 100 transmits the AI ​​sampling instruction frame 210. The extension input unit 110B receives the AI ​​sampling instruction frame 210 1.0 μsec after the control unit 100 transmits the AI ​​sampling instruction frame 210. Similarly, the extension input unit 110C receives the AI ​​sampling instruction frame 210 1.2 μsec after the control unit 100 transmits the AI ​​sampling instruction frame 210.

[0046] In step S430, each expansion input unit 110 delays the execution of sampling based on the value of the wait time 303 included in the received AI sampling instruction frame 210. For example, the expansion input unit 110A delays the execution of sampling by 3.5 μsec after receiving the AI ​​sampling instruction frame 210. The expansion input unit 110B delays the execution of sampling by 4.0 μsec after receiving the AI ​​sampling instruction frame 210. Similarly, the expansion input unit 110C delays the execution of sampling by 3.8 μsec after receiving the AI ​​sampling instruction frame 210.

[0047] In step S440, each extension input unit 110 starts sampling after the time specified by the value of the wait time 303 has elapsed. That is, the extension input units 110A, 110B, and 110C simultaneously perform sampling after the fixed time 400 has elapsed from the start of transmission of the AI ​​sampling instruction frame 210. When following the value of the wait time table 300 in FIG. 3, each extension input unit 110 simultaneously performs sampling after 5 μs has elapsed from the start of transmission of the AI ​​sampling instruction frame 210. When each extension input unit 110 is connected to multiple current / voltage sensors 130, it can acquire multiple pieces of AI data (sampling data).

[0048] In step S450, the control unit 100 acquires a timestamp indicating the timing at which the fixed time 400 has elapsed since the start of transmission of the AI ​​sampling instruction frame 210. This timestamp is the timing at which each of the extended input units 110 starts to simultaneously perform sampling. In practice, the processes of steps S440 and S450 can be performed almost simultaneously.

[0049] In step S460, each extension input unit 110 transmits the AI ​​data frame 220 storing the acquired AI data to the control unit 100. In step S470, the control unit 100 receives the AI ​​data frame 220 from each extension input unit 110. In step S480, the control unit 100 assigns the timestamp acquired in step S450 to the AI ​​data frame 220 received from each extension input unit 110. The control unit 100 may also associate each of the AI ​​data frames 220 assigned with the same timestamp as a measurement result at the same timing and use it to detect an abnormality in the equipment. In a certain aspect, the control unit 100 may determine whether or not there is an abnormality in the equipment based on whether or not each of the acquired AI data is equal to or greater than a predetermined threshold stored in the memory 102 (or whether or not each AI data satisfies a predetermined condition, etc.).

[0050] As described above, each extended input unit 110 can synchronize the execution timing of the sampling process by delaying the execution timing of sampling based on the waiting time set for each.

[0051] Also, it has been found that each extended input unit 110 starts sampling after a fixed time 400 has elapsed from the transmission timing of the AI sampling instruction frame 210. Therefore, the control unit 100 only needs to obtain the timestamp from the clock circuit 104 after the fixed time has elapsed from the transmission timing of the AI sampling instruction frame 210 and add the received timestamp to the sampled data. By doing so, complex synchronization or timing adjustment processes between the control unit 100 and each extended input unit 110 become unnecessary, and the extended input unit 110 can be realized with a simple configuration.

[0052] Furthermore, no matter how many extended input units 110 increase, the control unit 100 can easily synchronize the sampling start timing of each extended input unit 110 according to the procedure described with reference to FIG. 4.

[0053] <C. Measurement Function of Transmission Delay Time> Next, with reference to FIGS. 5 to 8, the measurement procedure for the transmission delay time between the control unit 100 and the extended input unit 110 will be described. The transmission delay time here indicates the one-way delay between the control unit 100 and each extended input unit 110.

[0054] FIG. 5 is a diagram showing an example of the hardware configuration of the extension unit communication circuit 105 and the communication circuit 111. The extension unit communication circuit 105 includes a transmission circuit 501, a reception circuit 502, and a transmission / reception time measurement circuit 503. The transmission circuit 501 transmits a frame to the reception circuit 511 via the transmission path 120. The reception circuit 502 receives a frame from the transmission circuit 517 via the transmission path 120. The transmission / reception time measurement circuit 503 acquires a timestamp of the transmission timing of the frame by the transmission circuit 501 and a timestamp of the reception timing of the frame by the reception circuit 502. In a certain aspect, the transmission / reception time measurement circuit 503 may request the time from the clock circuit 104 at the timing of transmission / reception. Alternatively, the transmission / reception time measurement circuit 503 may incorporate a timer circuit and measure the delay time between transmission and reception by setting the start of transmission as the Start of the timer and the end of reception as the Stop of the timer.

[0055] The communication circuit 111 includes a receiving circuit 511, a receiving memory 513, an I / F circuit 514, a transmitting memory 515, a transmitting circuit 517, and a cut-through path 518. The receiving circuit 511 receives frames from the transmitting circuit 501 via the transmission path 120. The receiving circuit 511 may also decode the received frames. The receiving memory 513 temporarily stores the frames received by the receiving circuit 511. In one aspect, the receiving memory 513 may store data obtained by decoded the frames. In another aspect, the receiving memory 513 may store the frames themselves.

[0056] I / F circuit 514 may transfer the frames (or decoded data) stored in reception memory 513 and the AI ​​data (sampling data) acquired from AI circuit 112 to other circuits depending on the purpose. Transmission memory 515 temporarily stores frames to be transmitted from transmission circuit 517. In one aspect, transmission memory 515 may store data before encoding. In another aspect, transmission memory 515 may store the encoded frames themselves. Transmission circuit 517 transmits the frames to reception circuit 502 via transmission path 120. In addition, transmission circuit 517 may encode the data to be transmitted.

[0057] The cut-through path 518 connects the receiving circuit 511 and the transmitting circuit 517. Usually, a frame is transmitted and received via a route 530. In other words, the frame passes through the receiving memory 513, the I / F circuit 514, and the transmitting memory 515. The storage time of the frame in the receiving memory 513 and the transmitting memory 515, and the transfer processing time of the frame in the I / F circuit 514, etc., may vary greatly because they are influenced by other data, etc. For this reason, in measuring the transmission delay time, the communication circuit 111 uses a route 540 that passes only through the receiving circuit 511, the cut-through path 518, and the transmitting circuit 517.

[0058] The measurement frame 550 includes a setting bit 560 for enabling and disabling the cut-through path in the header area. It is assumed that the receiving circuit 511 receives the measurement frame 550 including the setting bit 560 for enabling the cut-through path. In this case, the receiving circuit 511 transfers the measurement frame 550 to the transmitting circuit 517 via the cut-through path 518. Then, the transmitting circuit 517 returns the measurement frame 550 to the receiving circuit 502 via the transmission path 120. In one aspect, the transmitting circuit 517 may transmit the measurement frame 550 received by the receiving circuit 511 as it is. In another aspect, the transmitting circuit 517 may transmit a response frame to the measurement frame 550 received by the receiving circuit 511. The CPU 101 may obtain a timestamp at the time of transmission of the measurement frame 550 and a timestamp at the time of reception (RTT (Round-Trip Time) of the measurement frame 550) from the transmission / reception time measurement circuit 503. Alternatively, if the transmission / reception time measurement circuit 503 has a built-in timer circuit, the CPU 101 may acquire a timer measurement value (RTT of the measurement frame 550) from the transmission / reception time measurement circuit 503 during the period from the start of transmission to the end of reception of the measurement frame 550. In another aspect, when the communication circuit 111 uses the cut-through path 518, the reception circuit 511 may not need to perform the decoding process and the transmission circuit 517 may not need to perform the encoding process.

[0059] Fig. 6 is a diagram showing a first example of components of a delay time that occurs when transmitting and receiving the measurement frame 550. With reference to Fig. 6, the components of the delay time that occurs when transmitting and receiving the measurement frame 550 and a method of calculating the communication delay time between the control unit 100 and the extended input unit 110 will be described.

[0060] Components of the delay time occurring when transmitting and receiving the measurement frame 550 include a delay 651 in the transmitting circuit 501, a delay 652 on the outbound path in the transmission line 120, a delay 653 in the cut-through path 518, a delay 654 on the return path in the transmission line 120, and a delay 655 in the receiving circuit 502. Note that the delay 653 in the cut-through path 518 includes a transfer delay in the receiving circuit 511, the cut-through path 518, and the transmitting circuit 517.

[0061] Of the delays 651 to 655, the delays 651, 653, and 655 are approximately fixed times. The delays 652 and 654 in the transmission path 120 depend on the laying length of the transmission path 120. The CPU 101 of the control unit 100 can obtain only the round-trip delay in the transmission path 120 by subtracting the delays 651, 653, and 655 from the RTT (round-trip time) of the measurement frame 550. Furthermore, the CPU 101 can obtain the communication delay time between the control unit 100 and the extension input unit 110 (the value of the transmission delay time 302 in the latency table 300) by halving the value of the round-trip delay in the transmission path 120 (dividing it by 2 or multiplying it by 0.5).

[0062] 7 is a diagram showing an example of a communication flow when cut-through path 518 is not used. When the cut-through path is disabled by setting bit 560, receiving circuit 511 does not use cut-through path 518, and transfers a frame to route 740 via receiving memory 513 and I / F circuit 514. Also, receiving circuit 511 executes a decoding process on the received frame. Transmitting circuit 517 executes an encoding process on the data to be transmitted.

[0063] Fig. 8 is a diagram showing a second example of components of delay time occurring during transmission and reception of the measurement frame 550. The components of delay time shown in Fig. 8 include delays in decoding and encoding processes, unlike the components of delay time shown in Fig. 6. The components of delay time occurring during transmission and reception of the measurement frame 550 shown in Fig. 8 include delays 850 in decoding process in the receiving circuit 511 and delay 855 in encoding process in the transmitting circuit 517, in addition to delays 651 to 655. These delays 850 and 855 are approximately fixed times.

[0064] The CPU 101 of the control unit 100 can obtain only the round trip delay in the transmission path 120 by subtracting the delays 651, 850, 653, 855, and 655 from the RTT of the measurement frame 550. Furthermore, the CPU 101 can obtain the communication delay time between the control unit 100 and the extended input unit 110 (the value of the transmission delay time 302 in the latency table 300) by halving the value of the round trip delay in the transmission path 120 (dividing it by 2 or multiplying it by 0.5).

[0065] As described above, the control unit 100 and each extension input unit 110 can accurately and easily calculate the transmission delay time by measuring the communication time using the cut-through path 518. Furthermore, in the process of calculating the transmission delay time, only the control unit 100 needs to be equipped with the clock circuit 104 or a timer circuit, and the extension input unit 110 can be realized with a simple configuration.

[0066] As described above, the monitoring system 10 according to the present embodiment can easily and accurately calculate the transmission delay time between the control unit 100 and each extended input unit 110 by using the cut-through path 518. Furthermore, the monitoring system 10 can synchronize the sampling start times of each extended input unit 110 by using the obtained transmission delay time.

[0067] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. In addition, the disclosure contents described in the embodiments and each modified example are intended to be implemented, as far as possible, either alone or in combination. [Explanation of symbols]

[0068] 10 monitoring system, 100 control unit, 101 CPU, 102 memory, 103 network I / F circuit, 104 clock circuit, 105 expansion unit communication circuit, 106 DIO circuit, 107, 112 AI circuit, 110, 110A, 110B, 110C expansion input unit, 111 communication circuit, 120 transmission path, 130 current / voltage sensor, 210 AI sampling instruction frame, 211, 221 flag, 212, 222 command, 213, 223 sequence number, 214, 303 waiting time, 220 AI data frame, 224 AI data, 300 waiting time table, 301 unit number, transmission delay time, 400 fixed time, 501, 517 transmission circuit, 502, 511 reception circuit, 503 transmission / reception time measurement circuit, 513 reception memory, 514 I / F circuit, 515 transmission memory, 518 cut-through path, 530, 540 routes, 550 measurement frame, 560 setting bit.

Claims

1. A number of expansion units for sampling monitoring items of the facility; a control unit connected to each of the plurality of expansion units via a transmission line and configured to monitor the facility; The control unit Sending a first sampling instruction to a first extension unit among the plurality of extension units; Transmitting a second sampling instruction to a second extension unit among the plurality of extension units at the same timing as the transmission of the first sampling instruction; The first sampling instruction includes information of a first latency based on a first transmission delay time between the control unit and the first extension unit, The second sampling instruction includes information of a second latency based on a second transmission delay time between the control unit and the second extension unit, The first expansion unit includes: starting a sampling process after the first waiting time has elapsed since receiving the first sampling instruction; Sending a first sampling result to the control unit; The second expansion unit includes: After receiving the second sampling instruction and after the second waiting time has elapsed, starting a sampling process at the same timing as the start of the sampling process in the first extension unit; Sending the second sampling result to the control unit; The control unit A clock circuit is provided. Calculating the first latency time by subtracting the first transmission delay time from a fixed time; Calculating the second latency time by subtracting the second transmission delay time from the fixed time; acquiring a time stamp from the clock circuit after the fixed time has elapsed since transmitting the first sampling instruction and the second sampling instruction; A monitoring system that adds the timestamp to each of the received first sampling result and the second sampling result.

2. The monitoring system of claim 1 , wherein the control unit associates the first sampling result and the second sampling result based on a timestamp of the first sampling result being the same as a timestamp of the second sampling result.

3. The control unit Transmitting measurement data for measuring a transmission delay time to the first extension unit and the second extension unit, respectively; receiving the measurement data from the first expansion unit and the second expansion unit which have received the measurement data; The clock circuit measures a total transmission delay time from the transmission time of the measurement data to the reception time of the measurement data, 2. The monitoring system according to claim 1, further comprising: a monitoring unit configured to calculate the first transmission delay time and the second transmission delay time based on the total transmission delay time.

4. A number of expansion units for sampling monitoring items of the facility; a control unit connected to each of the plurality of expansion units via a transmission line and configured to monitor the facility; The control unit Sending a first sampling instruction to a first extension unit among the plurality of extension units; Sending a second sampling instruction to a second extension unit among the plurality of extension units; The first sampling instruction includes information of a first latency based on a first transmission delay time between the control unit and the first extension unit, The second sampling instruction includes information of a second latency based on a second transmission delay time between the control unit and the second extension unit, The first expansion unit includes: starting a sampling process after the first waiting time has elapsed since receiving the first sampling instruction; Sending a first sampling result to the control unit; The second expansion unit includes: starting a sampling process after the second waiting time has elapsed since receiving the second sampling instruction; Sending the second sampling result to the control unit; The control unit Calculating the first latency time by subtracting the first transmission delay time from a fixed time; Calculating the second latency time by subtracting the second transmission delay time from the fixed time; The control unit A clock circuit is provided. acquiring a time stamp from the clock circuit after the fixed time has elapsed since transmitting the first sampling instruction and the second sampling instruction; adding the time stamp to each of the received first sampling result and the received second sampling result; The control unit Transmitting measurement data for measuring a transmission delay time to the first extension unit and the second extension unit, respectively; receiving the measurement data from the first expansion unit and the second expansion unit which have received the measurement data; The clock circuit measures a total transmission delay time from the transmission time of the measurement data to the reception time of the measurement data, Calculating the first transmission delay time and the second transmission delay time based on the total transmission delay time; The expansion unit includes: A receiving circuit; A transmission circuit; a receiving memory for storing received data; a transmission memory for storing data to be transmitted; a path connecting the receiving circuit and the transmitting circuit without passing through the receiving memory and the transmitting memory; the measurement data includes a setting to enable the path, The expansion unit, upon receiving the measurement data, returns the measurement data via the receiving circuit, the path, and the transmitting circuit.

5. 5. The monitoring system of claim 4, wherein calculating the first transmission delay time and the second transmission delay time includes subtracting a transmission and reception delay by the control unit, a delay in the receiving circuit, a delay in the transmitting circuit, and a delay in the path from the total transmission delay time.

6. 5. The monitoring system of claim 4, wherein calculating the first transmission delay time and the second transmission delay time includes subtracting a transmission and reception delay by the control unit, a delay in the receiving circuit, a delay in the transmitting circuit, a delay in a decoding process, a delay in an encoding process, and a delay in the path from the total transmission delay time.

7. The monitoring system according to any one of claims 1 to 6, wherein the control unit detects an abnormality in the equipment based on determining whether each of the first sampling result and the second sampling result is equal to or greater than a predetermined threshold value.

8. A method for monitoring equipment, comprising: A control unit transmits a first sampling instruction to a first extension unit via a transmission path; The control unit transmits a second sampling instruction to a second extension unit via the transmission path at the same timing as the transmission of the first sampling instruction, The first sampling instruction includes information of a first latency based on a first transmission delay time between the control unit and the first extension unit, The second sampling instruction includes information of a second latency based on a second transmission delay time between the control unit and the second extension unit, The monitoring method further comprises: The first extension unit starts a sampling process after the first waiting time has elapsed since receiving the first sampling instruction; the first extension unit sending a first sampling result to the control unit; A step in which the second extension unit starts a sampling process at the same timing as the start of the sampling process in the first extension unit after the second waiting time has elapsed since receiving the second sampling instruction; the second extension unit sending a second sampling result to the control unit; the control unit calculating the first latency time by subtracting the first transmission delay time from a fixed time; the control unit calculating the second latency time by subtracting the second transmission delay time from the fixed time; acquiring a timestamp after the fixed time has elapsed since the control unit transmitted the first sampling instruction and the second sampling instruction; and a step of the control unit adding the timestamp to each of the received first sampling result and the second sampling result.

9. 9. The monitoring method of claim 8, further comprising the step of: the control unit associating the first sampling result and the second sampling result based on a timestamp of the first sampling result being the same as a timestamp of the second sampling result.

10. The control unit transmits measurement data for measuring a transmission delay time to the first extension unit and the second extension unit, respectively; The control unit receives the measurement data from the first expansion unit and the second expansion unit, respectively; a step of the control unit measuring a total transmission delay time from a transmission time of the measurement data to a reception time of the measurement data; The monitoring method according to claim 8 , further comprising: the control unit calculating the first transmission delay time and the second transmission delay time based on the total transmission delay time.

11. A method for monitoring equipment, comprising: A control unit transmits a first sampling instruction to a first extension unit via a transmission path; The control unit transmits a second sampling instruction to a second extension unit via the transmission path; The first sampling instruction includes information of a first latency based on a first transmission delay time between the control unit and the first extension unit, The second sampling instruction includes information of a second latency based on a second transmission delay time between the control unit and the second extension unit, The monitoring method further comprises: The first extension unit starts a sampling process after the first waiting time has elapsed since receiving the first sampling instruction; the first extension unit sending a first sampling result to the control unit; The second extension unit starts a sampling process after the second waiting time has elapsed since receiving the second sampling instruction; the second extension unit transmitting a second sampling result to the control unit; the control unit calculating the first latency time by subtracting the first transmission delay time from a fixed time; and the control unit calculates the second latency time by subtracting the second transmission delay time from the fixed time, acquiring a timestamp after the fixed time has elapsed since the control unit transmitted the first sampling instruction and the second sampling instruction; and the control unit adding the timestamp to each of the received first sampling result and the second sampling result; The control unit transmits measurement data for measuring a transmission delay time to the first extension unit and the second extension unit, respectively; The control unit receives the measurement data from the first expansion unit and the second expansion unit, respectively; a step of the control unit measuring a total transmission delay time from a transmission time of the measurement data to a reception time of the measurement data; The control unit further includes a step of calculating the first transmission delay time and the second transmission delay time based on the total transmission delay time; the expansion unit includes a path for connecting the receiving circuit and the transmitting circuit without passing through the receiving memory and the transmitting memory; the measurement data includes a setting to enable the path, The monitoring method further includes a step of the expansion unit returning the measurement data via the receiving circuit, the path, and the transmitting circuit based on receipt of the measurement data.

12. 12. The monitoring method according to claim 11, wherein the step of calculating the first transmission delay time and the second transmission delay time includes the step of subtracting a transmission and reception delay by the control unit, a delay in the receiving circuit, a delay in the transmitting circuit, and a delay in the path from the total transmission delay time.

13. 12. The monitoring method according to claim 11, wherein the step of calculating the first transmission delay time and the second transmission delay time includes the step of subtracting a transmission and reception delay by the control unit, a delay in the receiving circuit, a delay in the transmitting circuit, a delay in a decoding process, a delay in an encoding process, and a delay in the path from the total transmission delay time.

14. The monitoring method according to any one of claims 8 to 13, further comprising a step of detecting an abnormality in the facility based on whether or not each of the first sampling result and the second sampling result is equal to or greater than a predetermined threshold.

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