WO2015132899A1 - 異常検知システム及び異常検知方法 - Google Patents
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- G01K11/324—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres using Raman scattering
Definitions
- the present invention relates to an abnormality detection system and an abnormality detection method.
- an abnormality detection system including a temperature distribution measuring device (Distributed Temperature Sensor: DTS) that uses an optical fiber as a temperature sensor may be employed.
- DTS distributed Temperature Sensor
- an optical fiber is laid around a pipe or tank, and the end of the optical fiber is connected to a temperature distribution measuring device. Then, laser light is incident on the optical fiber from the temperature distribution measuring device, and the Raman scattered light generated in the optical fiber is detected by the temperature distribution measuring device to obtain the temperature of the pipe, tank, etc. Determine if there is an abnormality.
- An object of the present invention is to provide an abnormality detection system and an abnormality detection method capable of detecting abnormalities occurring in facilities such as chemical plants, refineries and thermal power plants at an early stage.
- an optical fiber is connected to one end side and the other end side of the optical fiber, and light is incident on the optical fiber from the one end side, and a first intensity distribution of backscattered light
- a backscattered light detector for acquiring a second intensity distribution of backscattered light by making light incident on the optical fiber from the other end side, the first intensity distribution, and the second intensity distribution.
- an anomaly detection system including a data processing unit that calculates transmission loss at each position in the length direction of the optical fiber by using a normalization function and determines the presence or absence of an abnormality from the calculation result.
- light is incident from one end side of the optical fiber to acquire a first intensity distribution of backscattered light, and light is incident from the other end side of the optical fiber to be rearward.
- a transmission loss is calculated at each position in the length direction of the optical fiber by using the step of obtaining the second intensity distribution of the scattered light, the first intensity distribution, the second intensity distribution, and the normalization function. And a step of determining whether or not there is an abnormality from the calculation result.
- an anomaly occurring in a facility such as a chemical plant, a refinery factory, or a thermal power plant can be detected at an initial stage.
- FIG. 1 is a view showing a state in which an optical fiber is wound with a constant tension around a portion where a branch pipe is welded to a main pipe.
- FIG. 2 is a diagram showing the results of examining transmission loss when a moderate bending is applied to an optical fiber, when a slightly strong bending is applied, and when a strong bending is applied.
- FIG. 3 is a diagram specifically illustrating moderate bending, slightly strong bending, and strong bending.
- FIG. 4 is a diagram illustrating a result of second-order differentiation of the intensity distribution of the backscattered light illustrated in FIG.
- FIG. 5 is a block diagram illustrating the abnormality detection system according to the embodiment.
- FIG. 6A is a diagram showing a state where one end side of the optical fiber and the beam splitter are optically connected
- FIG. 6B is an optical view between the other end side of the optical fiber and the beam splitter. It is a figure which shows the state connected.
- FIG. 7 is a diagram showing the intensity distribution of the first backscattered light NTS1 and the intensity distribution of the second backscattered light NTS2.
- FIG. 8 is a diagram showing the relationship between the temperature distribution (actual temperature distribution) when a part of the optical fiber is heated to 450 ° C. and the intensity distribution of the backscattered light NTS1, NTS2.
- FIG. 9 is an image diagram (part 1) for explaining the normalization function suppression function.
- FIG. 10 is an image diagram (part 2) for explaining the normalization function suppression function.
- FIG. 11 is a diagram illustrating an example of the normalization function.
- FIG. 12 is a flowchart illustrating an abnormality detection method by the abnormality detection system according to the embodiment.
- FIG. 13 is a diagram illustrating the intensity distribution of the backscattered light NTS1 and NTS2 and the normalized backscattering fluctuation.
- FIG. 14 is a diagram illustrating an example of the FIR filter.
- FIG. 15 is a diagram showing the normalized backscattering fluctuation after the FIR filter processing together with the intensity distribution of the backscattered light NTS1 and NTS2 and the normalized backscattering fluctuation before the FIR filter processing.
- FIG. 16 is a flowchart showing an example of a method for determining the phase of the backscattered light NTS1, NTS2.
- FIG. 17 is a diagram illustrating the intensity distribution of the backscattered light NTS1 and NTS2 and the functions FIRNTS1 and FIRNTS2.
- FIG. 18 is a diagram showing an experimental method for confirming that the stress can be measured by the optical fiber.
- FIGS. 19A to 19C are diagrams showing the normalized backscatter fluctuation and the normalized backscatter fluctuation after the FIR filter processing.
- FIG. 20 is a diagram showing the relationship between tensile stress on the horizontal axis and the peak height of normalized backscattering fluctuation after FIR filter processing on the vertical axis.
- FIG. 21 is a block diagram illustrating an example of a chemical plant monitoring system to which the abnormality detection system according to the embodiment is applied.
- FIG. 22 is a diagram showing availability 1.
- FIG. 23 is a flowchart showing generation of an alarm in the abnormality detection system.
- FIG. 24 is a diagram showing availability 2.
- an abnormality is detected by utilizing the fact that the transmission loss of the optical fiber changes due to the application of stress.
- FIG. 1 is a view showing a state in which an optical fiber 13 is wound with a constant tension around a portion where a branch pipe 12 is welded to a main pipe 11.
- the optical fiber 13 is partially fixed to the branch wiring 12 with a tape 14.
- the flow of liquid or gas in the main pipe 11 and branch pipe 12 changes, and the temperature of the main pipe 11 and branch pipe 12 changes. Due to this temperature change, the main pipe 11 and the branch pipe 12 expand or contract, and the bending stress or tensile stress applied to the optical fiber 13 changes.
- the optical fiber 13 has a large transmission loss when a bending stress or a tensile stress exceeding a certain level is applied. Therefore, for example, it is possible to determine whether there is an abnormality by comparing the transmission loss at the time of past operation or stop and the current transmission loss.
- the horizontal axis indicates the position in the length direction of the optical fiber
- the vertical axis indicates the intensity distribution of the backscattered light (backscattered light amount).
- the moderate bending is the bending shown in FIG. 3A (bending radius is about 10 mm), and the slightly stronger bending is slightly stronger than FIG. 3A (see FIG. 3B).
- the strong bend is a slightly stronger bend than that shown in FIG. 3B (see FIG. 3C).
- the intensity of the backscattered light is normalized based on the light amount at a position of 0 m in the length direction of the optical fiber.
- FIG. 2 shows that transmission loss corresponding to the degree of bending occurs at a position of about 340 m in the length direction of the optical fiber.
- the optical fiber is moderately bent during normal operation and a certain amount of transmission loss occurs at a specific position in the length direction of the optical fiber. In this case, if the transmission loss of the optical fiber changes rapidly, it can be determined that some abnormality has occurred.
- Patent Document 1 describes the second-order differentiation of the intensity distribution of backscattered light for the purpose of measuring the position and connection loss of an optical fiber with high accuracy. It is conceivable to use this method for detecting the presence or absence of abnormality.
- FIG. 4 is a diagram showing a result of second-order differentiation of the intensity distribution of the backscattered light shown in FIG.
- a one-dot chain line in FIG. 4 indicates a range of 3 ⁇ ( ⁇ is a standard deviation).
- the threshold value in order to remove noise components, it is necessary to set the threshold value to about 3 ⁇ .
- the threshold value is set to 3 ⁇ , the peak level of the middle bending portion is slightly higher than the noise level, and it cannot be said that the detection reliability is high.
- FIG. 2 shows that the difference in the amount of backscattered light before and after the position where a slightly strong bend is applied is about 2.4%.
- the occurrence of abnormality cannot be detected accurately unless there is a change in light quantity of 2.4% or more due to bending stress or tensile stress.
- the method of detecting the abnormality by second-order differentiation of the intensity distribution of the backscattered light cannot detect the abnormality until the transmission loss becomes large to some extent, that is, the problem that the abnormality cannot be detected at the initial stage. is there.
- an anomaly detection system and an anomaly detection method capable of detecting an anomaly occurring in a facility such as a chemical plant, a refinery factory, or a thermal power plant at an initial stage will be described.
- FIG. 5 is a block diagram illustrating the abnormality detection system according to the embodiment.
- the anomaly detection system includes a loop photodetection device 20 and a data processing device 30 that processes data output from the loop photodetection device 20.
- the loop-type photodetector 20 is an example of a backscattered light detector
- the data processor 30 is an example of a data processor.
- the loop type light detection device 20 includes a laser light source 21, a beam splitter 22, a transmission path switch 23, a light detection circuit unit 24, and a calculation unit 25, and is connected to an optical fiber 26 for use. Both ends of the optical fiber 26 are connected to the transmission path switch 23, and are laid around the pipes 11 and 12 as shown in FIG. 1 and partially fixed to the pipes 11 and 12 with a tape 14 or the like.
- Laser light with a predetermined pulse width is output from the laser light source 21 at a constant cycle.
- the laser light passes through the beam splitter 22 and enters the optical fiber 26 via the transmission path switch 23.
- the transmission path switch 23 switches the laser light transmission path at a constant cycle. That is, the transmission path switch 23 is in a state where one end side of the optical fiber 26 and the beam splitter 22 are optically connected (see FIG. 6A), and the other end side of the optical fiber 26 and the beam splitter 22. Are alternately switched to the state in which they are optically connected (see FIG. 6B).
- a part of the light that has entered the optical fiber 26 is backscattered by molecules constituting the optical fiber 26.
- the backscattered light returns through the optical fiber 26 and reaches the beam splitter 22 through the transmission path switch 23. Then, the light is reflected by the beam splitter 22 and reaches the light detection circuit unit 24.
- the photodetection circuit unit 24 is provided with a filter (not shown) that separates light of a predetermined wavelength and a light receiving element (not shown) that receives light of a predetermined wavelength separated by the filter. An electric signal corresponding to the intensity of the light received by the light receiving element is output from the light detection circuit unit 24.
- the calculation unit 25 includes a computer.
- the arithmetic unit 25 stores changes with time of the signal output from the light detection circuit unit 24 and outputs the data to the data processing device 30.
- the data processing device 30 is also configured to include a computer.
- the data processing device 30 processes the data output from the light detection device 20 to determine whether there is an abnormality as will be described later, and executes a preset process such as generating an alarm when it is determined as abnormal. To do.
- An optical pulse detector (Optical Time Domain Reflectometer: OTDR) that uses Rayleigh scattered light may be used as the loop-type photodetector 20, and Raman scattered light (Stokes light and anti-Stokes light) is used.
- a temperature distribution measuring device (DTS) may be used. When a temperature distribution measuring device is used as the light detection device 20, the temperature distribution can be measured together with the detection of the abnormality.
- the inventors of the present application have proposed a temperature measurement method for performing correction calculation using a transfer function for a temperature distribution detected by an optical fiber (Patent Document 3, etc.). According to this method, the temperature of the measurement points set at intervals of 10 cm to several tens of cm along the length direction of the optical fiber can be detected with high accuracy.
- FIG. 7 shows the intensity distribution of the first backscattered light NTS1 by taking the position of the optical fiber 26 in the length direction on the horizontal axis and the amount of backscattered light detected by the light detection device 20 on the vertical axis. It is a figure which shows intensity distribution of 2nd backscattered light NTS2.
- the horizontal axis in FIG. 7 indicates a predetermined position on the laser light source 21 side as a reference position in a state where the optical detection device 20 and one end side of the optical fiber 26 are optically connected as shown in FIG. (0m) is the distance from the reference position. Further, the transmission loss at the positions indicated by A1 and A2 in FIG. 7 is caused by a connector that optically connects between the light detection device 20 and one end side and the other end side of the optical fiber 26.
- the amount of the backscattered light NTS1 when the laser light is incident from one end of the optical fiber 26 is higher near the reference position (0 m position) and decreases as the distance from the reference position is increased.
- the amount of the backscattered light NTS2 when the laser light is incident from the other end of the optical fiber 26 is lower near the reference position and increases as the distance from the reference position is increased.
- FIG. 8 is a diagram showing the relationship between the temperature distribution (actual temperature distribution) when a partial section of the optical fiber 26 is heated to 450 ° C. and the intensity distribution of the backscattered light NTS1, NTS2.
- a portion of about 92 m to about 100 m of the optical fiber 26 is heated to about 450 ° C., and an external force is applied to a position of about 120 m. Further, the step at the 81.5 m position of the optical fiber 26 is due to the optical fiber connecting portion (connector).
- the direction of change in the amount of light of the backscattered light NTS1, NTS2 is the same (hereinafter referred to as “in-phase”) where a large temperature difference occurs (about 92m to about 100m). The gain is almost the same.
- the direction of change in the amount of the backscattered light NTS1, NTS2 is reversed (hereinafter referred to as "reverse phase”) at a location where an abnormality due to external force has occurred (about 120 m).
- the backscattered light NTS1 and NTS2 may be in the same phase as shown in FIG. 8, but a large transmission loss occurs. In this case, the backscattered light NTS1 and NTS2 are in opposite phases.
- the portion of the backscattered light NTS1, NTS2 having the opposite phase is either a portion where an abnormality is caused by an external force or a portion where a large transmission loss is generated at the optical fiber connection portion.
- an abnormality due to an external force is an abnormality in transmission loss caused by some external force acting on the optical fiber, such as tension, bending, or twisting.
- the intensity distribution of the backscattered light NTS1, NTS2 is normalized using a normalization function in order to detect anomalies due to external forces.
- a normalization function By giving this normalization function a suppression function, the influence of the temperature gradient is reduced.
- the distance from one end face of the optical fiber 26 is L, and a light pulse is made incident from one end face of the optical fiber 26 at a certain time t1.
- the intensity distribution of the backscattered light is normalized by its maximum value to obtain the L function NTS1 (L).
- the intensity distribution of the backscattered light obtained by making the light pulse incident from the other end face of the optical fiber 26 at the time t2 adjacent to the time t1 is also normalized by the maximum value, and the L function NTS2 (L).
- the condition (3) is that either the value of NTS1 (L) or the value of NTS2 (L) depends on whether the point of interest is near one end face side of the optical fiber 26 or near the other end face side. This is because one may be larger than the other. Even if the gain is the same value, for example, the intensity of the light pulse incident from one end face side of the optical fiber 26 is reduced. It becomes easy to receive.
- the step generated in the normalized backscattering fluctuation is small. Therefore, at the position where a large step occurs in the normalized backscattering fluctuation, either the transmission state of the optical fiber connection part is not good, a large transmission loss has occurred, or a transmission loss due to external force has occurred. It can be said.
- the position of the optical fiber connection part is managed when the optical fiber 26 is laid, it can be determined whether or not the position where the large step in the normalized backscattering fluctuation is the optical fiber connection part. . If the position where a large step is generated in the normalized backscattering fluctuation is not the optical fiber connection portion, it can be determined that an external force is applied to the position.
- a differential FIR (Finite Impulse Response) filter is used to emphasize the level difference of the normalized backscattering fluctuation.
- the differential FIR filter will be described later.
- FIG. 11 shows an example of the normalization function. This normalization function is expressed by the following equation (1).
- This equation (2) becomes the following equation (3) by canceling the denominator and the K of the numerator.
- the location affected by the ambient temperature and the location not affected by the ambient temperature have the same value.
- a function expressed by the following equation (4) using a sufficiently large real number A for non-zero NTS1 (L) and NTS2 (L) may be used.
- the denominator and numerator of equation (1) You may use the function of (5) Formula which replaced.
- FIG. 12 is a flowchart showing an abnormality detection method by the abnormality detection system according to this embodiment.
- the block diagrams of FIGS. 6A and 6B are also referred to.
- step S11 the data processing device 30 causes laser light to enter from one end side of the optical fiber 26 (see FIG. 6A), and acquires the intensity distribution of the backscattered light NTS1. Then, the data processing device 30 normalizes the intensity distribution of the backscattered light NTS1 with a reference value generated using the amount of laser light at the time of data acquisition, and obtains a function NTS1 (L) of the distance L.
- the light amount of the laser light measured by the light detection device may be used, and the normality or abnormality of the light amount of the laser light is judged from the output of the light detection device or the laser drive current, and normal If so, a predetermined value may be used.
- An average value or an integrated value can be used as the amount of laser light.
- the data processing device 30 causes the laser beam to enter from the other end of the optical fiber 26 (see FIG. 6B), acquires the intensity distribution of the backscattered light NTS2, and generates it by the same method as the NTS1.
- the function NTS2 (L) of the distance L is obtained by normalizing with the reference value.
- step S12 the data processing device 30 calculates a normalization function for each distance using NTS1 (L) and NTS2 (L), and generates a standardized backscattering fluctuation.
- FIG. 13 is a diagram showing the intensity distribution of the backscattered light NTS1 and NTS2 and the normalized backscattering fluctuation.
- the step due to the temperature gradient of the intensity distribution of the backscattered light NTS1 and NTS2 is suppressed, and the connector portion (position of about 81.5 m) and stress are applied.
- a large step occurs in the portion (position of about 120 m).
- step S13 the process proceeds to step S13, and the data processing device 30 causes a differential FIR filter to act (convolution) on the normalized backscattering fluctuation. Then, the absolute value of the result of applying the FIR filter is taken as the normalized backscattering fluctuation after the FIR filter processing.
- a differential FIR filter is a filter having a differentiation function and a high-frequency cutoff function by weighted smoothing.
- An example of the FIR filter used in this embodiment is shown in FIG.
- the FIR filter is 0 at the origin, is point-symmetric with respect to the origin, has an absolute value that increases as it approaches the origin, and approaches 0 as it moves away from the origin. Use a function.
- FIG. 15 is a diagram showing the normalized backscattering fluctuation after the FIR filter processing together with the intensity distribution of the backscattered light NTS1 and NTS2 and the normalized backscattering fluctuation before the FIR filter processing.
- step S14 the data processing device 30 extracts a peak where the maximum value exceeds the threshold value from the graph of the normalized backscattering fluctuation after the FIR filter processing.
- the threshold value is set to 10 times that. Thereby, the peak by the influence of the temperature gradient which exists in the position of about 92m and about 103m remove
- the threshold value may be set arbitrarily according to the system design, and may not be 10 times the background noise.
- the peak is treated as noise accompanying the large peak. This is because the distance resolution of the present system is about 1 m, and if there is a large peak and a small peak within ⁇ 2 m, the small peak is likely to be a large peak noise. Further, even if the small peak and the large peak are caused by different abnormalities, it is considered that there is no problem even if an alarm is generated as the same abnormalities.
- step S15 the data processing device 30 determines whether or not the backscattered light NTS1 and NTS2 are in reverse phase at the peak position.
- the determination as to whether or not the backscattered light NTS1 and NTS2 are in reverse phase is a local maximum value of a predetermined magnitude or more after a second-order differentiation is performed on the intensity distribution of the backscattered light NTS1 and NTS2, respectively.
- step S15 when it is determined that the backscattered light NTS1 and NTS2 are in phase (in the case of NO), the process proceeds to step S19.
- step S19 the data processing device 30 stores the peak as a result of the optical fiber connection unit. Thereafter, the process proceeds to step S20.
- step S15 if it is determined in step S15 that the backscattered light NTS1 and NTS2 are in opposite phases at the peak position (in the case of YES), the process proceeds to step S16.
- step S16 the data processing device 30 refers to the laying data and determines whether or not the peak position is the optical fiber connection portion.
- a peak larger than the threshold value occurs at a position of 80.5 m.
- the laying data it is recorded that there is a connector at a position of 81.5 m.
- There is a difference of 1 m between the peak position of the standardized backscattering fluctuation after the FIR processing and the connector position of the laying data but this difference is within the range of ⁇ 2 m described above.
- the peak at the position of 80.5 m is determined to be due to the optical fiber connection. Therefore, in this case (YES in step S16), the process proceeds to step S19.
- the data processing device 30 stores the peak at the position of 80.5 m as a transmission loss due to the optical fiber connection unit. Thereafter, the process proceeds to step S20.
- step S20 the data processing device 30 performs a system check.
- the data processing device 30 refers to past data to check whether or not the transmission loss amount in the optical fiber connection portion has changed significantly. When it is determined that the amount of transmission loss has not changed significantly, the process ends with no abnormality. Further, when it is determined that the transmission loss has changed significantly, it is considered that some abnormality has occurred in the optical fiber connection portion, and therefore the data processing device 30 executes processing such as generating an alarm.
- step S16 determines whether the peak position is not the optical fiber connection part (in the case of NO)
- the process proceeds to step S17.
- step S17 the data processing device 30 stores the peak located at 119.5 m as a transmission loss due to the application of external force.
- step S17 the process proceeds from step S17 to step S18, and the data processing apparatus 30 performs sign analysis.
- the data processing device 30 compares past data with a transmission loss amount (for example, the magnitude of the detection signal in FIG. 13) due to the application of external force. If the amount of transmission loss is the same as when there is no abnormality in the past, the process ends with no abnormality.
- a transmission loss amount for example, the magnitude of the detection signal in FIG. 13
- the data processing device 30 performs processing such as generating an alarm indicating abnormality. Note that an alarm may be generated when the amount of transmission loss due to the application of an external force deviates from a preset range.
- a sensitivity three times or more is obtained as compared with the method of second-order differentiation of the intensity distribution of the backscattered light (see FIG. 4). For this reason, according to the present embodiment, it is possible to detect an abnormality occurring in a facility such as a chemical plant, a refinery factory, or a thermal power plant at an initial stage, and it is possible to prevent a serious accident.
- step S21 the data processing device 30 causes a differential FIR filter to act (convolution) on the intensity distribution of the backscattered light NTS1 and NTS2.
- a differential FIR filter is applied to the intensity distributions of the backscattered light NTS1 and NTS2, a function (graph) having a peak corresponding to a change in the amount of light with little noise is obtained.
- a filter having the characteristics shown in FIG. 14 is used as the differential FIR filter.
- FIRNTS1 a function obtained by applying the FIR filter to the intensity distribution of the backscattered light NTS1
- a function obtained by applying the FIR filter to the intensity distribution of the backscattered light NTS2 is referred to as FIRNTS2.
- FIG. 17 is a diagram showing the intensity distribution of the backscattered light NTS1 and NTS2 and the functions FIRNTS1 and FIRNTS2.
- the function FIRNTS1 has a positive peak at positions of about 80 m, about 100 m, and about 120 m, and has a negative peak at a position of about 92 m.
- the function FIRNTS2 has a positive peak at a position of about 100 m, and has negative peaks at positions of about 80 m, about 92 m, and about 120 m.
- step S22 the data processing unit 30 performs multiplication (multiplication) of the peak value at each peak position of the functions FIRNTS1 and FIRNTS2. Then, it transfers to step S23 and it is determined whether a calculation result is negative for every peak position.
- step S23 If it is determined in step S23 that the calculation result is negative (in the case of YES), the process proceeds to step S24, where the change in the amount of the backscattered light NTS1, NTS2 at the peak position is determined to be in reverse phase, and step S15 in FIG. Return to.
- step S23 If it is determined in step S23 that the calculation result is 0 or positive (in the case of NO), the process proceeds to step S25, where the change in the light amount of the backscattered light NTS1, NTS2 at the peak position is determined to be the same phase. Return to step S15 of step 12.
- the calculation result is a negative value at positions of about 80 m and about 120 m, and is a positive value at positions of about 92 m and about 100 m. That is, it can be seen that the change in the amount of light of the backscattered light NTS1 and NTS2 is in the opposite phase at the positions of about 80 m and about 120 m and in the same phase at the positions of about 92 m and about 100 m.
- three circular bobbins 31a, 31b, 32 having a radius larger than the minimum allowable bending radius of the optical fiber 26 were prepared. Then, the bobbins 31a and 31b were fixed to a support (not shown), the optical fiber 26 was hung between the bobbins 31a and 31b, and the bobbin 32 was arranged at the center.
- a spring alone (not shown) is attached to the bobbin 32, and the bobbin 32 is pulled downward through the spring alone so that a desired tensile stress can be applied to the optical fiber 26 between the bobbins 31a and 31b. Further, the optical fiber 26 and the bobbins 31a and 31b are joined with a tape so that tensile stress is applied only to the optical fiber 26 between the bobbins 31a and 31b.
- Both ends of the optical fiber 26 are connected to the photodetector 20 (see FIG. 5), the intensity distribution of the backscattered light NTS1 and NTS2 is measured, and data processing is performed by the data processing device 30 (see FIG. 5) to perform normalized backscattering. Normalization backscatter variation after variation and FIR treatment was obtained. It was confirmed that NTS1 (L) and NTS2 (L) were in antiphase when obtaining normalized backscattering fluctuations.
- the horizontal axis represents the position of the optical fiber
- the vertical axis represents the temperature and the peak height of the normalized backscattering fluctuation after FIR filter processing, that is, the detection signal. It is a figure which shows a relationship.
- FIG. 20 is a diagram showing the relationship between the tensile stress on the horizontal axis and the peak height of normalized backscattering fluctuation after FIR filter processing on the vertical axis.
- FIG. 19A is a graph when a medium tensile stress is applied to the bobbin 32
- FIG. 19B is a graph when a tensile stress twice that of FIG. 19A is applied
- FIG. 19 (c) is a graph when a tensile stress of 2.8 times that in FIG. 19 (a) is applied.
- the peak near 98 m is due to the tensile stress.
- FIG. 20 shows that the peak height of the detection signal changes in a quadratic function with respect to the tensile stress.
- FIG. 21 is a block diagram showing an example of a chemical plant monitoring system to which the abnormality detection system according to the present embodiment is applied.
- the 21 includes an abnormality detection system 40 that monitors whether there is an abnormality in the chemical reaction tower 41 and the piping 42, and a monitoring control system 50 that performs state monitoring and control of the entire chemical plant.
- the optical fiber 26 is laid on the outer surface of the chemical reaction tower 41 and a pipe 42 connected to the chemical reaction tower 41, and the optical fiber 26, the light detection device 20, and the data processing device 30.
- the abnormality detection system 40 is constructed.
- This anomaly detection system 40 updates the history of transmission loss of the optical fiber 26, thereby causing abnormal expansion or contraction due to deformation of the piping 42, breakage at the joint, and malfunction of the chemical reaction tower 41. Etc. are detected.
- the abnormality detection system 40 activates the monitoring alarm lamp 44 or a buzzer to notify the operator of the abnormality.
- a temperature distribution measurement device (DTS) is used as the light detection device 20, and the temperature distribution in the length direction of the optical fiber 26 can be measured.
- the temperature data of the preset section is sent to the I / O device 53 via the external contact 43, and is used for opening / closing control of the electromagnetic valve 54, for example.
- the abnormality detection system 40 is connected to the monitoring control system 50 via the transmission control LAN 55.
- the monitoring control system 50 includes a monitoring control server 51 that monitors the states of the I / O devices 53 and the abnormality detection system 40 via the transmission control LAN 55, and a monitoring operation connected to the monitoring control server 51 via the man-machine LAN 56. And a table 52. The state of each place in the plant can be monitored by the monitoring console 52, and the electromagnetic valve 54 and the like can be operated via the I / O device 53.
- the abnormality detection system 40 is connected to the monitoring control system 50, it is configured independently as a local system. This is to prevent other parts from being affected even if the abnormality detection system 40 stops for some reason.
- FIGS. 22A to 22D show examples in which the abnormality detection system described in the embodiment is applied to abnormality detection of a pipe connection portion as shown in FIG.
- FIG. 22 (a) it is assumed that a high-temperature liquid or gas flows in the main pipe 61 during plant operation.
- the main pipe 61 expands during plant operation, and the main pipe 61 contracts when the plant is stopped.
- the data processor 30 stores the loss amount of the optical fiber 26 during plant operation and shutdown.
- reference numeral 64 denotes a tape for fixing the optical fiber 26
- 65 denotes a heat insulating material and a protective pipe arranged around the main pipe 61.
- the normal operation is performed next time as shown in FIG. 22 (c). Rather than the branch pipe 52 is pushed out. Then, as shown in FIG. 22D, when the next stop state is reached, the optical fiber 26 is pulled without returning the pushed branch pipe 62, and an abnormality is detected by the abnormality detection system.
- FIG. 23 is a flowchart showing generation of an alarm in the abnormality detection system.
- step S31 when a peak equal to or higher than the threshold value is detected in step S31 (see FIG. 15), the process proceeds to step S32 to determine whether or not the peak location is different from the previous time. If the peak location is the same as the previous time in step S32 (in the case of YES), the process proceeds to step S33, and if the peak location is not the same as the previous time (in the case of NO), the process proceeds to step S37.
- step S33 it is determined whether the backscattered light NTS1 and NTS2 are in reverse phase. In the case of the reverse phase (in the case of YES), the process proceeds to step S34, and in the case of the same phase (in the case of NO), the process proceeds to step S36.
- step S34 When the process proceeds from step S33 to step S34, the peak position and size are stored. And it transfers to step S35 and turns on a red lamp. The lighting of this red light indicates a loss abnormality due to external force.
- step S36 the yellow light is turned on. This yellow light indicates that there is an unregistered fusion splice point or the like.
- step S32 it is determined whether or not the peak position is not registered in the laying data. If not registered (in the case of YES), the process proceeds to step S38. If registered (in the case of NO), the process proceeds to step S41.
- step S38 it is determined whether there is a significant difference from the past data.
- the process proceeds to step S39 and the red light is turned on. The lighting of this red light indicates an increase in loss.
- step S38 If it is determined in step S38 that there is no significant difference from the past data (in the case of NO), the process proceeds to step S40 and the yellow light is turned on. The lighting of this yellow light indicates the remaining loss.
- step S41 it is determined whether there is a significant difference from the past data.
- step S42 the yellow light is turned on. The lighting of this yellow lamp indicates that the connection state of the fused part of the connector or the optical fiber has deteriorated.
- step S41 when it is determined in step S41 that there is no significant difference (in the case of NO), the process proceeds to step S43 and the green lamp is turned on.
- the green light indicates that the peak is due to a connector or the like and there is no abnormality.
- a minute change in transmission loss of the optical fiber can be captured and classified as being due to an external force or due to a connector or fusion. Then, transmission loss exceeding the set threshold value is sequentially registered as data, and used for instruction determination of the display level of the monitoring warning light at the next and subsequent data collection. Thereby, for example, it can be used as a health check function such as whether or not a large displacement has occurred in piping after an earthquake or the like occurs.
- FIG. 24 shows an example in which the abnormality detection system described in the embodiment is applied to the cultivation of high-quality fruits and theft prevention in a greenhouse.
- a temperature distribution measuring device DTS
- the temperature in the house is managed based on the measurement result.
- the temperature distribution measuring device is also used as the light detection device 20 in FIG. 5 and connected to the data processing device 30 to be used for detecting an abnormality.
- the optical fiber 26 wound around the melon 70 is to be unwound. If the thief works carefully, the optical fiber 26 will not be cut, but if the optical fiber 26 is to be unwound, the occurrence of a minute transmission loss is inevitable. Thereby, abnormality can be detected in the abnormality detection system.
- the abnormality detection system detects an abnormality
- the administrator is notified of the occurrence of the abnormality as the patrol lamp is turned on and the alarm buzzer is started. As a result, enormous damage can be suppressed.
- An optical fiber is attached to a bridge such as a railway bridge, and the abnormality of the bridge can be detected by the disclosed abnormality detection system. Thereby, for example, when an earthquake occurs, it is possible to determine whether there is an abnormality in the bridge, or to estimate the maintenance time.
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Abstract
Description
図5は、実施形態に係る異常検知システムを示すブロック図である。
図22(a)~(d)は、実施形態で説明した異常検知システムを図1に示したような配管接続部の異常検知に適用した事例を示している。
図24は、実施形態で説明した異常検知システムを、ビニールハウス内での高級果物の栽培及び盗難防止に適用した事例を示す。
鉄道の鉄橋等の橋梁に光ファイバを取り付け、開示した異常検知システムにより橋梁の異常を検知することができる。これにより、例えば地震が発生したときに橋梁の異常の有無を判定したり、メンテナンスの時期を見積もることができる。
Claims (21)
- 光ファイバと、
前記光ファイバの一端側及び他端側に接続され、前記一端側から前記光ファイバに光を入射して後方散乱光の第1の強度分布を取得し、前記他端側から前記光ファイバに光を入射して後方散乱光の第2の強度分布を取得する後方散乱光検出部と、
前記第1の強度分布及び前記第2の強度分布と規格化関数とを用いて前記光ファイバの長さ方向の各位置で伝送損失を計算し、その計算結果から異常の有無を判定するデータ処理部と
を有することを特徴とする異常検知システム。 - 前記規格化関数が、前記光ファイバの任意の位置Lにおける前記第1の強度分布の強度をK1・a(但し、aは前記第1の強度分布にピークがないと仮定したときの位置Lにおける強度)とし、前記第2の強度分布の強度をK2・b(但し、bは前記第2の強度分布にピークがないと仮定したときの位置Lにおける強度)としたときに、(1)K1=K2のときには一定値となり、(2)K1≠K2のときには前記一定値と異なる値となり、
前記第1の強度分布を規格化した関数をNTS1(L)、前記第2の強度分布を規格化した関数をNTS2(L)としたときに、(3)NTS1(L)/NTS2(L)を横軸(対数軸)としたときにNTS1(L)/NTS2(L)=1を中心軸とする偶関数であり、(4)NTS1(L)=NTS2(L)のときには最大値又は最小値をとり、どちらかが限りなくゼロに近づいても有限の値をもつ、という条件を満足することを特徴とする請求項1に記載の異常検知システム。 - 前記関数NTS1(L)及び前記関数NTS2(L)は、測定時のレーザ光の光量を用いて規格化されていることを特徴とする請求項2に記載の異常検知システム。
- 前記後方散乱光検出部が、温度分布測定装置(Distributed Temperature Sensor)又は光パルス検出器(Optical Time Domain Reflectmeter)であることを特徴とする請求項1乃至3のいずれか1項に記載の異常検知システム。
- 前記データ処理部は、前記関数NTS1(L)及び前記関数NTS2(L)を前記規格化関数に入力して得た規格化後方散乱変動に対し微分系の第1のFIR(Finite Impulse Response)フィルタを作用させた後にその絶対値をとって得た分布から、しきい値よりも大きな極大値のピークを抽出することを特徴とする請求項2に記載の異常検知システム。
- 前記データ処理部は、前記関数NTS1(L)及び前記関数NTS2(L)に対して微分系の第2のFIR(Finite Impulse Response)フィルタを作用させて得た結果同士の積が負の箇所を抽出することを特徴とする請求項5に記載の異常検知システム。
- 前記第1のFIRフィルタと前記第2のFIRフィルタが同一であることを特徴とする請求項6に記載の異常検知システム。
- 前記データ処理部は、敷設データに記録された光ファイバ接続部と前記負の箇所とを照合し、その結果に基づいて前記負の箇所が光ファイバ接続部か、前記光ファイバに応力が印加された箇所かを判定することを特徴とする請求項6に記載の異常検知システム。
- 前記データ処理部は、抽出後の前記しきい値よりも大きなピークのピーク高さから前記光ファイバに印加された応力を推定することを特徴とする請求項5に記載の異常検知システム。
- 前記データ処理部は、抽出後の前記しきい値よりも大きなピークのピーク高さを過去のデータと比較し、その結果に応じて異常か否かを判定することを特徴とする請求項5に記載の異常検知システム。
- 光ファイバの一端側から光を入射して後方散乱光の第1の強度分布を取得し、前記光ファイバの他端側から光を入射して後方散乱光の第2の強度分布を取得する工程と、
前記第1の強度分布及び前記第2の強度分布と規格化関数とを用いて前記光ファイバの長さ方向の各位置で伝送損失を計算し、その計算結果から異常の有無を判定する工程と
を有することを特徴とする異常検知方法。 - 前記規格化関数が、前記光ファイバの任意の位置Lにおける前記第1の強度分布の強度をK1・a(但し、aは前記第1の強度分布にピークがないと仮定したときの位置Lにおける強度)とし、前記第2の強度分布の強度をK2・b(但し、bは前記第2の強度分布にピークがないと仮定したときの位置Lにおける強度)としたときに、(1)K1=K2のときには一定値となり、(2)K1≠K2のときには前記一定値と異なる値となり、
前記第1の強度分布を規格化した関数をNTS1(L)、前記第2の強度分布を規格化した関数をNTS2(L)としたときに、(3)NTS1(L)/NTS2(L)を横軸(対数軸)としたときにNTS1(L)/NTS2(L)=1を中心軸とする偶関数であり、(4)NTS1(L)=NTS2(L)のときには最大値又は最小値をとり、どちらかが限りなくゼロに近づいても有限の値をもつ、という条件を満足することを特徴とする請求項13に記載の異常検知方法。 - 前記第1の強度分布及び前記第2の強度分布は、光パルス検出器(Optical Time Domain Reflectmeter:OTDR)又は温度分布測定装置(Distributed Temperature Sensor:DTS)を用いて取得することを特徴とする請求項13又は14に記載の異常検知方法。
- 前記関数NTS1(L)は前記第1の強度分布を前記第1の強度分布測定時のレーザ光の光量を用いて規格化したものであり、前記関数NTS2(L)は前記第2の強度分布を前記第2の強度分布測定時のレーザ光の光量を用いて規格化したものであることを特徴とする請求項15に記載の異常検知方法。
- 前記異常の有無を判定する工程は、
前記関数NTS1(L)及び前記関数NTS2(L)を前記規格化関数に入力して得た規格化後方散乱変動に対し微分系の第1のFIR(Finite Impulse Response)フィルタを作用させた後にその絶対値をとって得た分布から、しきい値よりも大きな極大値のピークを抽出する工程を含むことを特徴とする請求項13に記載の異常検知方法。 - 前記異常の有無を判定する工程は、
前記関数NTS1(L)及び前記関数NTS2(L)に対して微分系の第2のFIR(Finite Impulse Response)フィルタを作用させて得た結果同士の積が負の箇所を抽出する工程を含むことを特徴とする請求項17に記載の異常検知方法。 - 前記異常の有無を判定する工程は、
敷設データに記録された光ファイバ接続部と前記負の箇所とを照合し、その結果に基づいて前記負の箇所が光ファイバ接続部か、前記光ファイバに応力が印加された箇所かを判定する工程を含むことを特徴とする請求項18に記載の異常検知方法。
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AU2015394727A1 (en) * | 2015-05-13 | 2017-11-23 | Fujitsu Limited | Temperature measurement device, temperature measurement method, and temperature measurement program |
FR3084741B1 (fr) * | 2018-08-02 | 2021-05-21 | Inst De Radioprotection Et De Surete Nucleaire | Procede de determination de la deformation d'une structure de beton au cours du temps |
CN113167980B (zh) * | 2018-11-27 | 2022-08-26 | 深圳市大耳马科技有限公司 | 光纤传感器及其光强损耗值计算分析方法和装置 |
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JPH04332835A (ja) * | 1991-05-08 | 1992-11-19 | Agency Of Ind Science & Technol | 分布温度データの補正処理方法 |
JPH08247858A (ja) * | 1995-03-07 | 1996-09-27 | Toshiba Corp | 光温度分布センサ及び温度分布測定方法 |
US5592282A (en) * | 1993-07-22 | 1997-01-07 | York Limited | Suppression of stimulated scattering in optical time domain reflectometry |
JPH0918428A (ja) * | 1995-06-30 | 1997-01-17 | Ando Electric Co Ltd | 光ファイバの試験方法 |
JPH09329415A (ja) * | 1996-06-11 | 1997-12-22 | Nippon Tetsudo Kensetsu Kodan | 障害位置検出システム |
WO2010125712A1 (ja) * | 2009-05-01 | 2010-11-04 | 富士通株式会社 | 温度測定システム及び温度測定方法 |
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GB8520827D0 (en) * | 1985-08-20 | 1985-09-25 | York Ventures & Special Optica | Fibre-optic sensing devices |
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- 2014-03-05 JP JP2016505995A patent/JP6160766B2/ja active Active
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2016
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JPH04332835A (ja) * | 1991-05-08 | 1992-11-19 | Agency Of Ind Science & Technol | 分布温度データの補正処理方法 |
US5592282A (en) * | 1993-07-22 | 1997-01-07 | York Limited | Suppression of stimulated scattering in optical time domain reflectometry |
JPH08247858A (ja) * | 1995-03-07 | 1996-09-27 | Toshiba Corp | 光温度分布センサ及び温度分布測定方法 |
JPH0918428A (ja) * | 1995-06-30 | 1997-01-17 | Ando Electric Co Ltd | 光ファイバの試験方法 |
JPH09329415A (ja) * | 1996-06-11 | 1997-12-22 | Nippon Tetsudo Kensetsu Kodan | 障害位置検出システム |
WO2010125712A1 (ja) * | 2009-05-01 | 2010-11-04 | 富士通株式会社 | 温度測定システム及び温度測定方法 |
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JP6160766B2 (ja) | 2017-07-12 |
JPWO2015132899A1 (ja) | 2017-03-30 |
US10088342B2 (en) | 2018-10-02 |
AU2014385118A1 (en) | 2016-08-11 |
AU2014385118B2 (en) | 2017-04-06 |
US20160327415A1 (en) | 2016-11-10 |
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