CN120445456B - A distributed fiber optic temperature measurement system based on Raman scattering - Google Patents
A distributed fiber optic temperature measurement system based on Raman scatteringInfo
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- CN120445456B CN120445456B CN202510651319.9A CN202510651319A CN120445456B CN 120445456 B CN120445456 B CN 120445456B CN 202510651319 A CN202510651319 A CN 202510651319A CN 120445456 B CN120445456 B CN 120445456B
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Abstract
The invention relates to the field of fiber optics, in particular to a distributed fiber temperature measurement system based on Raman scattering, which comprises an optical signal excitation and separation module, a signal acquisition and preprocessing module, a temperature resolving module, a calibration and correction module, a real-time monitoring and early warning module and a management database, wherein the system monitors the optical power in real time by separating Stokes light and anti-Stokes light, the method comprises the steps of dividing space positions, carrying out digital accumulation and noise reduction on scattered signals, determining the space positions corresponding to the temperatures through resolving the temperatures, generating a temperature distribution curve, respectively selecting constant temperature reference points, fitting the temperature deviation curve to generate a calibration coefficient, correcting the temperatures, calibrating the calibration curve, compensating light intensity attenuation, and monitoring temperature abnormal points through setting multi-stage temperature early warning thresholds.
Description
Technical Field
The invention relates to the field of fiber optics, in particular to a distributed fiber temperature measurement system based on Raman scattering.
Background
Under the condition of various industries of digital and intelligent wave-tide mats, accurate temperature monitoring becomes a key guarantee for stable operation in various fields. In the power system, the overheat of the cable joint may cause fire, and if the heat dissipation of the server of the data center is poor, the data processing efficiency and the service life of the device will be affected.
The distributed optical fiber temperature measurement uses the optical fiber as a sensing unit, realizes long-distance and continuous distributed temperature monitoring by utilizing the scattering property of light, has the unique advantages of electromagnetic interference resistance, corrosion resistance, embedded installation and the like, can adapt to complex and severe monitoring environments, provides an innovative solution for the fields of industrial safety monitoring, energy efficient management, infrastructure health diagnosis and the like, becomes an important direction of the development of temperature monitoring technology, and plays an increasingly important role in promoting intelligent upgrading of various industries.
Although the distributed optical fiber temperature measurement technology shows huge application potential, the prior art still has a plurality of problems to be solved, for example, the prior China patent with the application number 201310017365.0 discloses a distributed optical fiber Raman temperature measurement system, the scheme is characterized in that the distributed optical fiber Raman temperature measurement system enters into a sensing optical fiber to be measured after passing through a wavelength division multiplexer, pulse laser continuously generates back scattering in the process of propagating in the optical fiber, the back scattering light returns to the wavelength division multiplexer, after being filtered by the wavelength division multiplexer, stokes Raman scattering light and anti-Stokes Raman scattering light are respectively filtered out and enter into a double-channel avalanche photodiode for photoelectric conversion, and an electric signal output by the double-channel avalanche photodiode is processed by a DSP digital signal processor to obtain a temperature signal, so that the processing speed is high, and the real-time performance of temperature measurement can be not influenced on the premise of ensuring the accuracy.
However, the scheme has the following defects that firstly, although the scheme has accumulation processing and wavelet denoising, a systematic method for space division is lacked, the position corresponding to the temperature cannot be accurately determined, and the hidden danger of local overheating of the optical fiber can be missed.
2. According to the scheme, the temperature is calculated only through a fixed formula, dynamic factors of the optical fiber characteristics changing along with time and environment are not considered, an updating mechanism for temperature calculation model parameters is lacked, and long-term use errors can be accumulated continuously.
3. The scheme does not mention a complete early warning mechanism, only depends on a temperature resolving result, lacks a multidimensional abnormality judging standard and a grading early warning function, cannot timely and accurately discover temperature abnormality, and is difficult to effectively guarantee the safety of a monitored object in practical application.
Disclosure of Invention
In order to overcome the defects in the background technology, the embodiment of the invention provides a distributed optical fiber temperature measurement system based on Raman scattering, which can effectively solve the problems related to the background technology.
The invention provides a Raman scattering-based distributed optical fiber temperature measurement system, which comprises an optical signal excitation and separation module, a laser output power automatic adjustment module and a power control module, wherein the optical signal excitation and separation module is used for separating Stokes light and anti-Stokes light through a beam splitter and a dual-wavelength optical filter, monitoring optical power in real time and automatically adjusting the laser output power.
The signal acquisition and preprocessing module is used for dividing the space position based on the optical time domain reflection principle, calculating the minimum accumulation frequency algorithm and carrying out digital accumulation noise reduction on the scattered signals.
The temperature calculating module is used for calculating the temperature through the ratio of the Stokes light intensity to the anti-Stokes light intensity, determining the corresponding spatial position of the temperature by utilizing the optical time domain reflection principle and generating a temperature distribution curve.
And the calibration correction module is used for respectively selecting the constant temperature reference points, fitting the temperature deviation curve to generate a calibration coefficient, correcting the temperature and calibrating the calibration curve, and compensating the light intensity attenuation.
The real-time monitoring and early warning module is used for setting a multi-stage temperature early warning threshold value, monitoring abnormal temperature points, recording abnormal information and triggering corresponding-stage early warning response.
The management database is used for storing the fiber attenuation coefficient, the constant temperature reference point temperature, the temperature calibration curve, the early warning threshold value, the temperature-position mapping table and the historical temperature data.
Preferably, the specific analysis method of the optical signal excitation and separation module comprises the steps of injecting laser pulses into the sensing optical fiber, primarily separating back scattering light generated when the laser pulses propagate in the sensing optical fiber through the beam splitter, and further separating Stokes light and anti-Stokes light by utilizing a dual-wavelength optical filter.
And monitoring the power of the separated Stokes light and anti-Stokes light, and triggering an alarm mechanism when the monitored optical power deviates from a set optical power reasonable range, and automatically adjusting the output power of the laser to compensate.
Preferably, the specific analysis method for dividing the space position is to preset a segmentation parameter of a single measurement scattering signal, wherein the segmentation parameter comprises a space position range corresponding to each data segment, and the space position range is determined based on an optical time domain reflection principle and combined with the length of a sensing optical fiber.
Based on the noise characteristic of the system and the target signal-to-noise ratio, the minimum accumulation times meeting the signal quality requirement are calculated, the optical pulse transmitting module is controlled to inject laser pulses into the sensing optical fiber, the laser pulses are excited to generate scattering signals containing temperature information, and the scattering signals are transmitted to the digital accumulation unit for photoelectric conversion and digital processing.
And carrying out time domain segmentation on the digitized scattered signals, wherein each time window corresponds to one data segment, each time window is converted into a specific spatial position area on the sensing optical fiber, and each segmented data segment is stored in a buffer area of a corresponding spatial position according to a corresponding relation.
Preferably, the specific analysis method of the minimum accumulation times comprises the steps of measuring the system output under the condition of no signal input to obtain the white noise power spectral density of the system, simultaneously determining the working bandwidth of the system and the absolute temperature of the working environment of the system, setting the target signal-to-noise ratio according to the temperature measurement precision requirement, and converting the target signal-to-noise ratio into a linear value from decibels, so that the minimum accumulation times meeting the signal quality requirement are obtained by a calculation formula of the minimum accumulation times.
Preferably, the specific analysis method for carrying out digital accumulation noise reduction on the scattered signals comprises the steps of carrying out multiple measurements according to the minimum accumulation times, generating scattered signal data segments corresponding to all spatial positions in each measurement, and storing the scattered signal data segments in corresponding buffer areas to form a plurality of groups of scattered signal data segmented according to the spatial positions.
And sequentially extracting each data segment corresponding to the multiple measurements aiming at the same spatial position buffer area, carrying out superposition summation on the numerical values of corresponding data points in multiple measurement signals of the same spatial position, and dividing the superposition signal summation by the measurement times to obtain the mean data point of the spatial position.
Traversing the data segments of all the spatial positions to generate a mean sequence containing mean data points of all the spatial positions.
Preferably, the specific analysis method of the spatial position corresponding to the temperature comprises the steps of respectively extracting a Stokes optical signal intensity value and an anti-Stokes optical signal intensity value corresponding to the same spatial position from the average value sequence, and calculating the ratio of the Stokes light intensity value to the anti-Stokes light intensity value to obtain a Raman scattering intensity ratio.
And calling a preset temperature calibration curve, wherein the calibration curve is a mapping relation between a Raman scattering intensity ratio and a temperature value, substituting the Raman scattering intensity ratio into the calibration curve, and calculating the temperature value of the corresponding space position.
Preferably, the specific analysis method of the temperature calculation module is that the starting time of the laser pulse injected into the sensing optical fiber by the optical pulse transmitting module is recorded, the receiving time of the scattered signal reaching the photoelectric conversion module is detected, and the time difference between the receiving time and the starting time is calculated.
And acquiring material refractive index parameters of the sensing optical fiber, multiplying the time difference by the light speed based on the optical time domain reflection principle, dividing the time difference by the doubled material refractive index, and calculating the spatial position distance corresponding to the scattering signal.
And mapping the space position distance into specific physical position coordinates on the sensing optical fiber, and establishing a one-to-one correspondence between the temperature value and the physical position coordinates.
And correlating the temperature values of all the space positions obtained by calculation in the same measurement period with corresponding physical position coordinates to generate a temperature-position mapping table, and generating a continuous temperature distribution curve based on the temperature-position mapping table by taking the physical position as a horizontal axis and the temperature value as a vertical axis.
Preferably, the specific analysis method of the calibration curve comprises the steps of setting constant temperature reference points with known temperatures at the initial end, the middle section and the tail end of the sensing optical fiber respectively, automatically collecting standard temperature values of the constant temperature reference points according to set time length, and recording the standard temperature values of the constant temperature reference points at all time points.
And according to the difference between the standard temperature value of each constant temperature reference point at each time point and the corresponding temperature value on the temperature calibration curve, forming a temperature deviation curve, fitting the temperature deviation curve, generating a calibration coefficient matrix, substituting the calibration coefficient matrix into a temperature correction formula, judging in real time according to the temperature fluctuation range, adopting a linear correction mode or a nonlinear correction mode, and recalibrating the temperature calibration curve by utilizing the corrected temperature value.
Preferably, the specific analysis method for compensating the light intensity attenuation comprises the steps of dividing a sensing optical fiber into a plurality of small sections with fixed length according to the length, obtaining initial attenuation coefficients of the sensing optical fibers of each section from a management database, establishing a model of the attenuation coefficients changing along with the temperature, approximately calculating accumulated attenuation quantity from the initial end of the sensing optical fiber to the position by adopting a trapezoid integration method aiming at a certain position on the sensing optical fiber, calculating a compensation factor according to the attenuation quantity, and compensating scattered light intensity at the position, thereby obtaining the finally compensated light intensity, and correcting the corresponding relation between the temperature value and the light intensity.
Preferably, the specific analysis method of the real-time monitoring and early warning module is that multistage temperature early warning thresholds are respectively set, when the temperature of a certain position of the sensing optical fiber is detected to exceed a certain stage early warning threshold, the position is judged to be a temperature abnormal point, and the temperature value of the abnormal point and the time for monitoring the abnormality are recorded.
Based on the calibrated and corrected temperature data, a multi-stage temperature early warning threshold is preset, wherein the multi-stage temperature early warning threshold comprises an absolute temperature threshold, a relative temperature threshold calculated based on historical temperature data and a temperature change rate threshold, the absolute temperature threshold is used for setting specific temperature values of different grades of early warning, the relative temperature threshold is calculated based on statistics such as the mean value, the standard deviation and the like of the historical temperature data, and the temperature change rate threshold is used for measuring the amplitude of temperature change in unit time.
And monitoring the temperature of each position of the sensing optical fiber in real time, and judging the position as a temperature abnormal point when the temperature of a certain position is detected to meet any one of the conditions that the temperature exceeds an absolute temperature threshold value, the temperature exceeds a relative temperature threshold value calculated based on historical temperature data and the temperature change rate exceeds a set temperature change rate threshold value.
After a certain position is judged to be a temperature abnormal point, the temperature value of the abnormal point and the time for monitoring the abnormality are recorded, the specific physical position coordinates of the abnormal point on the sensing optical fiber are obtained according to the temperature distribution curve, and the early warning responses of different grades are triggered according to the deviation degree of the temperature value of the abnormal point and a preset multi-stage temperature early warning threshold value.
Compared with the prior art, the invention has the following beneficial effects that firstly, the optical power can be monitored in real time by separating Stokes light from anti-Stokes light, the intensity information of an optical signal can be accurately obtained, and the scattered signal is subjected to digital accumulation and noise reduction by dividing the space position, so that the change condition of the light in the transmission process can be accurately analyzed.
2. According to the invention, the temperature is calculated through the ratio of the Stokes light intensity to the anti-Stokes light intensity, the corresponding spatial position of the temperature is determined by utilizing the optical time domain reflection principle, a temperature distribution curve is generated, the high-precision spatial positioning of the temperature distribution is realized, and the temperature conditions of different positions are accurately known.
3. According to the invention, the constant temperature reference points are respectively selected, the temperature deviation curve is fitted to generate the calibration coefficient, the temperature is corrected, the calibration curve is calibrated, and meanwhile, the light intensity attenuation is compensated, so that the influence of light intensity change on temperature measurement caused by loss and other reasons when light is transmitted in the optical fiber can be eliminated, and the stability of the light intensity is ensured.
4. According to the invention, by setting the multi-stage temperature early warning threshold, monitoring the temperature abnormal point, recording the abnormal information and triggering the corresponding grade early warning response, different countermeasures can be adopted according to the severity of the abnormality.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a diagram illustrating a system module connection according to the present invention.
Fig. 2 is a flowchart of dividing spatial locations in the signal acquisition and preprocessing module of fig. 1.
Fig. 3 is a flow chart of the temperature calculation module in fig. 1.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, a raman scattering-based distributed optical fiber temperature measurement system includes an optical signal excitation and separation module, a signal acquisition and preprocessing module, a temperature resolving module, a calibration and correction module, a real-time monitoring and early warning module, and a management database.
The system comprises a management database, a signal acquisition and preprocessing module, a temperature resolving module, a calibration correcting module and a real-time monitoring and early warning module, wherein the temperature resolving module is connected with the signal acquisition and preprocessing module and the calibration correcting module, the optical signal excitation and separation module is connected with the signal acquisition and preprocessing module, and the calibration correcting module is connected with the real-time monitoring and early warning module.
And the optical signal excitation and separation module is used for separating Stokes light and anti-Stokes light through the optical splitter and the dual-wavelength optical filter, monitoring the optical power in real time and automatically adjusting the output power of the laser.
The specific analysis method of the optical signal excitation and separation module comprises the steps of injecting laser pulses into a sensing optical fiber, primarily separating back scattering light generated when the laser pulses propagate in the sensing optical fiber through a beam splitter, further separating Stokes light and anti-Stokes light by utilizing a dual-wavelength optical filter, accurately separating out required optical signals, ensuring that the monitored optical power is in a reasonable range, improving the processing precision and stability of the optical signals of the system, and providing a reliable optical signal basis for the follow-up accurate measurement of temperature.
The power of separated Stokes light and anti-Stokes light is monitored, when the monitored light power deviates from the set reasonable range of the light power, an alarm mechanism is triggered, the output power of the laser is automatically adjusted to compensate, the stability of the light power is maintained, the accuracy and the reliability of system measurement are ensured, and the measurement error caused by the fluctuation of the light power is reduced.
The signal acquisition and preprocessing module is used for dividing the space position based on the optical time domain reflection principle, calculating the minimum accumulation frequency algorithm and carrying out digital accumulation noise reduction on the scattered signals.
Referring to fig. 2, the specific analysis method for dividing the spatial position is to preset the segmentation parameters of the single measurement scattering signal, wherein the segmentation parameters comprise the spatial position range corresponding to each data segment, the spatial position range is determined based on the optical time domain reflection principle and combined with the length of the sensing optical fiber, and the spatial position of the sensing optical fiber can be accurately divided, so that the basis is provided for accurately acquiring the temperature information of different positions subsequently.
Based on the noise characteristic of the system and the target signal-to-noise ratio, the minimum accumulation times meeting the signal quality requirement are calculated, the optical pulse transmitting module is controlled to inject laser pulses into the sensing optical fiber, the laser pulses are excited to generate scattering signals containing temperature information, the scattering signals are transmitted to the digital accumulation unit for photoelectric conversion and digital processing, and by determining the proper accumulation times, the signal quality can be improved, noise interference is reduced, the system can acquire and process the scattering signals more accurately, and therefore the temperature of each spatial position can be determined more accurately.
And carrying out time domain segmentation on the digitized scattered signals, wherein each time window corresponds to one data segment, each time window is converted into a specific spatial position area on the sensing optical fiber, and each segmented data segment is stored in a buffer area of a corresponding spatial position according to a corresponding relation.
The specific analysis method of the minimum accumulation times comprises the steps of measuring the system output under the condition of no signal input to obtain the white noise power spectral density of the system, simultaneously determining the working bandwidth of the system and the absolute temperature of the working environment of the system, setting a target signal-to-noise ratio according to the temperature measurement precision requirement, converting the target signal-to-noise ratio into a linear value, and substituting the linear value into a calculation formula of the minimum accumulation times to obtain the minimum accumulation times meeting the signal quality requirement, wherein the optimal measurement times can be determined according to the characteristics and the actual requirements of the system, the measurement process is optimized, the measurement efficiency is improved while the measurement precision is ensured, and the resource waste caused by unnecessary measurement times is avoided.
The formula for converting the target signal-to-noise ratio from decibels to linear values is as followsSubstituting it into formulaMinimum accumulation times meeting signal quality requirementsWhereinRepresenting the white noise power spectral density of the system,Indicating the absolute temperature of the system operating environment,Is the operating bandwidth of the system.
The specific analysis method for carrying out digital accumulation noise reduction on the scattered signals comprises the steps of carrying out multiple measurements according to the minimum accumulation times, generating scattered signal data segments corresponding to all spatial positions in each measurement, and storing the scattered signal data segments in corresponding buffer areas to form a plurality of groups of scattered signal data segmented according to the spatial positions.
And sequentially extracting each data segment corresponding to the multiple measurements aiming at the same spatial position buffer area, carrying out superposition summation on the numerical values of corresponding data points in multiple measurement signals of the same spatial position, and dividing the superposition signal summation by the measurement times to obtain the mean data point of the spatial position.
The method comprises the steps of traversing the data segments of all the space positions to generate a mean value sequence containing mean value data points of all the space positions, effectively reducing noise in scattered signals, improving the stability and accuracy of the signals by measuring the mean value for multiple times, and enabling the measurement result to be more reliable.
The temperature calculating module is used for calculating the temperature through the ratio of the Stokes light intensity to the anti-Stokes light intensity, determining the corresponding spatial position of the temperature by utilizing the optical time domain reflection principle and generating a temperature distribution curve.
The specific analysis method of the spatial position corresponding to the temperature comprises the steps of respectively extracting Stokes optical signal intensity values and anti-Stokes optical signal intensity values corresponding to the same spatial position from the average value sequence, and calculating the ratio of the Stokes light intensity values to the anti-Stokes light intensity values to obtain a Raman scattering intensity ratio.
The temperature of the corresponding space position can be accurately calculated through the known temperature calibration curve by utilizing the corresponding relation between the optical signal intensity ratio and the temperature, so that the accurate measurement of the temperature is realized.
The specific analysis method of the temperature calibration curve comprises the steps of carrying out multipoint calibration on the sensing fiber through a standard blackbody furnace in advance, and establishing a mapping relation between a Raman scattering intensity ratio and a temperature value by adopting a piecewise polynomial fitting method to form the temperature calibration curve.
Referring to fig. 3, the specific analysis method of the temperature calculation module includes recording a start time of laser pulse injected into the sensing fiber by the optical pulse emission module, detecting a receiving time of a scattered signal reaching the photoelectric conversion module, and calculating a time difference between the receiving time and the start time.
And acquiring material refractive index parameters of the sensing optical fiber, multiplying the time difference by the light speed based on the optical time domain reflection principle, dividing the time difference by the doubled material refractive index, and calculating the spatial position distance corresponding to the scattering signal.
The space position distance is mapped into specific physical position coordinates on the sensing optical fiber, the one-to-one correspondence relation between the temperature value and the physical position coordinates is established, the space position corresponding to the scattering signal can be accurately determined, the distribution condition of the temperature on the sensing optical fiber is intuitively presented, and the temperature can be monitored and analyzed comprehensively and accurately.
And correlating the temperature values of all the space positions obtained by calculation in the same measurement period with corresponding physical position coordinates to generate a temperature-position mapping table, and generating a continuous temperature distribution curve based on the temperature-position mapping table by taking the physical position as a horizontal axis and the temperature value as a vertical axis.
And the calibration correction module is used for respectively selecting the constant temperature reference points, fitting the temperature deviation curve to generate a calibration coefficient, correcting the temperature and calibrating the calibration curve, and compensating the light intensity attenuation.
The specific analysis method of the calibration curve comprises the steps of setting constant temperature reference points with known temperatures at the initial end, the middle section and the tail end of the sensing optical fiber respectively, automatically collecting standard temperature values of the constant temperature reference points according to set time length, and recording the standard temperature values of the constant temperature reference points at all time points.
And according to the standard temperature value of each constant temperature reference point at each time point and the corresponding temperature value on the temperature calibration curve, forming a temperature deviation curve, fitting the temperature deviation curve, generating a calibration coefficient matrix, substituting the calibration coefficient matrix into a temperature correction formula, judging in real time according to the temperature fluctuation range, adopting a linear correction mode or a nonlinear correction mode, and recalibrating the temperature calibration curve by utilizing the corrected temperature value, wherein the temperature calibration curve can be calibrated and corrected according to the actually measured temperature value, so that the temperature calibration curve is more in line with the actual situation, and the accuracy and reliability of temperature measurement are improved.
When the absolute value of the fluctuation of the set temperature is smaller than the set threshold value, a linear correction mode is adopted, and the formula of the linear correction mode is as followsWhen the absolute value of the fluctuation of the set temperature is larger than or equal to the set threshold value, adopting a nonlinear correction mode, wherein the formula of the nonlinear correction mode is as followsWhereinThe value of the standard temperature is indicated,The temperature after the correction is indicated,Is a matrix of calibration coefficients.
The specific analysis method for compensating the light intensity attenuation comprises the steps of dividing the sensing optical fiber into a plurality of small sections with fixed length according to the length, obtaining initial attenuation coefficients of the sensing optical fibers of each section from a management database, establishing a model of the attenuation coefficients changing along with temperature, approximately calculating the accumulated attenuation quantity from the initial end of the sensing optical fiber to the position by adopting a trapezoid integration method aiming at a certain position on the sensing optical fiber, calculating a compensation factor according to the attenuation quantity, compensating the scattered light intensity at the position, thus obtaining the finally compensated light intensity, correcting the corresponding relation between a temperature value and the light intensity, effectively compensating the influence of the light intensity attenuation on a measurement result, ensuring the accuracy of the light intensity, improving the accuracy of temperature measurement, and enabling the corresponding relation between the temperature value and the light intensity to be more accurate.
The model of the decay coefficient changing with temperature is thatWhereinIs the firstThe initial attenuation coefficient of the length of optical fiber,,For a temperature dependent attenuation coefficient (typical value 0.002 dB/km/C),For the change of the ambient temperature, for a certain position on the sensing optical fiber, the cumulative attenuation from the initial end of the sensing optical fiber to the position is approximately calculated by adopting a trapezoidal integral methodWhereinIs thatThe sequence number of the segment in which it is located,Respectively the firstSegment, the firstThe initial attenuation coefficient of the segment fiber calculates the compensation factor according to the attenuation amountFor the scattered light intensity at that locationAnd (3) compensating: Obtaining the final compensated light intensity 。
The real-time monitoring and early warning module is used for setting a multi-stage temperature early warning threshold value, monitoring abnormal temperature points, recording abnormal information and triggering corresponding-stage early warning response.
The specific analysis method of the real-time monitoring and early warning module comprises the steps of respectively setting multi-stage temperature early warning thresholds, judging that a certain position of the sensing optical fiber is a temperature abnormal point when the temperature of the position exceeds the certain-stage early warning threshold, and recording the temperature value of the abnormal point and the time for monitoring the abnormality.
Based on the calibrated and corrected temperature data, a multi-stage temperature early warning threshold is preset, wherein the multi-stage temperature early warning threshold comprises an absolute temperature threshold, a relative temperature threshold calculated based on historical temperature data and a temperature change rate threshold, the absolute temperature threshold is used for setting specific temperature values of different grades of early warning, the relative temperature threshold is calculated based on statistics such as the mean value, the standard deviation and the like of the historical temperature data, and the temperature change rate threshold is used for measuring the amplitude of temperature change in unit time.
And monitoring the temperature of each position of the sensing optical fiber in real time, and judging the position as a temperature abnormal point when the temperature of a certain position is detected to meet any one of the conditions that the temperature exceeds an absolute temperature threshold value, the temperature exceeds a relative temperature threshold value calculated based on historical temperature data and the temperature change rate exceeds a set temperature change rate threshold value.
After a certain position is judged to be a temperature abnormal point, the temperature value of the abnormal point and the time for monitoring the abnormality are recorded, the specific physical position coordinates of the abnormal point on the sensing optical fiber are obtained according to the temperature distribution curve, and the early warning response of different grades is triggered according to the deviation degree of the temperature value of the abnormal point and the preset multi-grade temperature early warning threshold value.
The specific content of the early warning response of different grades is that when the proportion of the temperature exceeding the absolute temperature threshold or the degree exceeding the relative temperature threshold reaches the set first-level early warning standard, the first-level early warning is triggered, the local audible and visual warning is carried out, and a short message notification is sent to relevant operation and maintenance personnel.
When the proportion of the temperature exceeding the absolute temperature threshold or the degree exceeding the relative temperature threshold reaches a set secondary early warning standard, triggering secondary early warning, starting emergency lighting, increasing the monitoring frequency of the system to 1 second/time, and pushing popup window reminding to related personnel through an application program.
When the temperature exceeds the absolute temperature threshold value or the degree of exceeding the relative temperature threshold value reaches the set three-level early warning standard or the temperature reaches the material tolerance limit temperature, triggering three-level early warning, closing the equipment power supply related to the abnormal point in a linkage way, starting the fire-fighting spraying system, and sending emergency notification to all related responsible persons.
The management database is used for storing the fiber attenuation coefficient, the constant temperature reference point temperature, the temperature calibration curve, the early warning threshold value, the temperature-position mapping table and the historical temperature data.
While embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention, which is also intended to be covered by the present invention.
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