CN111365623B - Negative pressure wave inflection point identification method based on linear fitting - Google Patents
Negative pressure wave inflection point identification method based on linear fitting Download PDFInfo
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- CN111365623B CN111365623B CN202010155928.2A CN202010155928A CN111365623B CN 111365623 B CN111365623 B CN 111365623B CN 202010155928 A CN202010155928 A CN 202010155928A CN 111365623 B CN111365623 B CN 111365623B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
- F17D5/005—Protection or supervision of installations of gas pipelines, e.g. alarm
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
- F17D5/02—Preventing, monitoring, or locating loss
- F17D5/06—Preventing, monitoring, or locating loss using electric or acoustic means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
- G01L11/025—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means using a pressure-sensitive optical fibre
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
- G01M3/26—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors
- G01M3/28—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for pipes, cables or tubes; for pipe joints or seals; for valves ; for welds
- G01M3/2807—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for pipes, cables or tubes; for pipe joints or seals; for valves ; for welds for pipes
- G01M3/2815—Investigating fluid-tightness of structures by using fluid or vacuum by measuring rate of loss or gain of fluid, e.g. by pressure-responsive devices, by flow detectors for pipes, cables or tubes; for pipe joints or seals; for valves ; for welds for pipes using pressure measurements
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- General Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Examining Or Testing Airtightness (AREA)
Abstract
The invention belongs to the technical field of pipeline leakage detection, and relates to a negative pressure wave inflection point identification method based on linear fitting. The method comprises the steps of respectively selecting appropriate data to perform linear fitting on a stationary section of a negative pressure wave denoising signal before leakage of a pipeline and a descending section of the negative pressure wave denoising signal after leakage of the pipeline; the inflection point of the negative pressure wave is rapidly and accurately obtained by solving the intersection point of the two straight lines. The method improves the accuracy and speed of identifying the inflection point of the negative pressure wave on the premise of keeping the signal characteristics of the original negative pressure wave as much as possible, has simple principle, can be directly embedded into most program systems, and has low cost and wide application range. The real-time online detection of the negative pressure wave inflection point and other pipeline leakage detection and positioning methods related to negative pressure wave inflection point identification have positive significance in the aspects of leakage point positioning accuracy and positioning speed.
Description
Technical Field
The invention belongs to the technical field of pipeline leakage detection, and relates to a negative pressure wave inflection point identification method based on linear fitting.
Background
The pipeline is just like a life line and bears the important task of safely transporting petroleum, natural gas, water resources and the like and relating to national civilian resources. However, as the service life of the pipeline increases, pipeline leakage often occurs due to corrosion, aging, weld defects, geological condition changes, third party damage, and the like. Especially for long-distance high-pressure pipelines, once the pipelines leak, the leakage amount is large, the repair difficulty is high, the destructiveness and the harmfulness of the pipelines are far larger than those of low-level pipelines, and serious leakage accidents are caused. Therefore, the leakage phenomenon of the high-pressure pipeline is detected in time, the leakage position of the pipeline is accurately positioned, and the method has practical significance for safe operation of the pipeline, guarantee of life and property safety of people and reduction of environmental pollution.
At present, a plurality of methods for researching leakage and positioning of the pipeline exist, and the main methods comprise a pressure gradient method, a sound wave method, a vibration signal method and a negative pressure wave method. Among these methods, the negative pressure wave method has become one of the main means for detecting the leakage of the pipeline at present because of its characteristics of simple principle and sensor arrangement and relatively accurate measurement. The pipeline leakage detection and positioning method based on the negative pressure wave method mainly comprises the step of obtaining the arrival time difference of the negative pressure waves acquired by the sensor to position a leakage point, so that the arrival time of the negative pressure waves acquired by the sensor is required to be as accurate as possible.
The time of arrival of the negative pressure wave is determined by the time of occurrence of the inflection point of the negative pressure wave, however, the current methods for identifying the inflection point of the negative pressure wave are few and mainly focus on a threshold method and a singular point identification method. The threshold value method is too conservative, so that the negative pressure wave inflection point identification is delayed frequently, and the positioning error is large. The singular point identification method is used for identifying the singular point of the negative pressure wave signal instead of identifying the inflection point so as to determine the arrival time of the negative pressure wave. However, it requires multi-scale wavelet transformation of the negative pressure wave signal, which causes singular point deviation as the scale increases, thereby causing measurement errors; in addition, the workload is large, the calculation time is long, and the position of the pipeline leakage occurring cannot be located at the first time. Therefore, the method for accurately and rapidly identifying the inflection point of the negative pressure wave has important practical significance.
Disclosure of Invention
In order to solve the problems, the invention provides a negative pressure wave inflection point identification method based on linear fitting. The negative pressure wave signals are basically kept stable before leakage by analyzing a large amount of denoised pipeline leakage negative pressure wave signals; after the leakage occurs, the negative pressure wave signal is linearly decreased. It is like a sudden turning of a horizontal straight line, a new straight line is formed, and the intersection point of the two straight lines is the inflection point of the negative pressure wave. By solving the inflection point, the time of arrival of the negative pressure wave can be obtained more accurately.
The technical scheme of the invention is as follows:
a negative pressure wave inflection point identification method based on linear fitting comprises the following specific steps:
step 1: and de-noising the negative pressure wave signal generated by the pipeline leakage and acquired by the sensor.
Step 2: selecting P time points and corresponding data values of the denoising signal stationary section obtained by the processing in the step 1 for linear fitting to obtain a straight line L1＝a1t+b1。
And step 3: and averaging the data values corresponding to the P selected time points to set the data values as a leakage threshold S.
And 4, step 4: and comparing the data values of all points in all the data of the negative pressure wave signal with S in sequence from small to large according to the corresponding time. When the data values corresponding to the N continuous time points are lower than the set S, the pipeline leakage is considered to occur; extracting the 1 st time point of the N time points, and performing linear fitting on the next M time points and corresponding data values thereof to obtain a straight line L2＝a2t+b2。
And 5: solving two straight lines L1And L2The intersection point of the two points is the inflection point of the negative pressure wave, so that the time t (b) when the sensor detects the arrival of the negative pressure wave can be obtained2-b1)/(a1-a2)。
The invention has the advantages that: according to the negative pressure wave inflection point identification method based on linear fitting, on the premise that denoising processing is carried out only once and original negative pressure wave signals are not greatly changed, original signal characteristics are kept as far as possible, and the negative pressure wave inflection point identification accuracy is improved. The method has simple principle, can be directly embedded into most program systems, and has the advantages of high detection speed, low cost and wide application range. The real-time online detection of the negative pressure wave inflection point and other pipeline leakage detection and positioning methods related to negative pressure wave inflection point identification have positive significance in the aspects of leakage point positioning accuracy and positioning speed.
Drawings
Fig. 1 is a schematic diagram of a negative pressure wave inflection point identification method based on linear fitting.
Fig. 2 is a partially enlarged view of the inflection point position of the negative pressure wave in fig. 1.
In the figure: 1 denoising a signal; 2 straight line L1＝a1t+b1(ii) a 3 straightLine L2＝a2t+b2(ii) a 4 negative pressure wave inflection point.
Detailed Description
The following detailed description of the invention refers to the accompanying drawings.
The schematic diagram of the negative pressure wave inflection point identification method based on linear fitting is shown in fig. 1.
The specific process is as follows:
step 1: two fiber grating pressure sensors are respectively arranged at two ends of one gas transmission steel pipeline, and the fiber grating sensors are selected because of high sensitivity, so that the method has higher measurement precision. The data acquisition equipment is a fiber grating demodulator, and the sampling frequency is 1000 Hz. And (3) carrying out denoising processing on a negative pressure wave signal generated by the pipeline leakage and acquired by one of the sensors to obtain a denoising signal 1 shown in fig. 1. The wavelet transformation is used for the denoising processing of the negative pressure wave signal, the denoising method can obviously reduce the time-course noise of the negative pressure wave signal, the details of the original signal are still reserved, and the solving precision of the method is further improved.
Step 2: as can be seen from the denoised signal 1 in FIG. 1, the stationary part of the denoised signal 1 is about 6000 points, and the inflection point of the negative pressure wave appears between about 6000 and 8000 points. And selecting a numerical value close to the inflection point of the predicted negative pressure wave to perform linear fitting, so that the inflection point identification precision is higher. Thus, according to the method, the value of P is chosen to be 1000, specifically from the 5000 th point to the 6000 th point of the de-noised signal 1. Performing linear fitting on the 1000 time points and the corresponding data values to obtain a straight line L1＝a1t+b 1 2。
And step 3: averaging the data values corresponding to the 1000 time points selected in step 2, and setting the average as a leakage threshold
And 4, step 4: for each point data value in all the data of the negative pressure wave signal, the data values are sequentially matched with the data values of all the points in the sequence from small to large according to the corresponding time
A comparison is made. When the data values corresponding to N continuous time points are lower than the set data values
The pipeline leakage is considered to occur; extracting the 1 st time point of the N time points, and performing linear fitting on the next M time points and corresponding data values thereof to obtain a straight line L2＝a2t+b 2 3。
If the value N is set to be too small, the method is too sensitive, and pipeline vibration or fluid disturbance in the pipeline can be identified as leakage to generate false alarm; if the setting is too large, the calculation amount is increased, and the time for identifying the inflection point of the negative pressure wave is prolonged. The value of M is not suitable to be set to be too large, because the pressure is suddenly increased due to the upstream flow compensation after the negative pressure wave passes through, the measured value is increased to some extent, and the leakage section straight line L is formed2＝a2t+b 23, certain fluctuation occurs, and the accuracy of linear fitting is influenced.
As can be seen from the de-noising signal 1 in fig. 1, the descending section of the de-noising signal 1 of the negative pressure wave has about 5000 points, and according to the method, the value of N is set to 1000; as can be seen from the denoised signal 1 in fig. 2, a certain rising fluctuation occurs in the measured value between 6900 th point and 7000 th point of the descent segment, so the value M should not be too large, and is set to 100. If in different pipeline models and practical engineering application, appropriate N and M values are set according to the characteristics of the pipeline leakage signal so as to ensure the measurement accuracy of the algorithm.
And 5: solving two straight lines L1And L2The intersection point of (a) is the inflection point 4 of the negative pressure wave, so that the time t (b) when the sensor detects the arrival of the negative pressure wave can be obtained2-b1)/(a1-a2). According to the method, the arrival time of the negative pressure wave is calculated to be 6.843 s. And (5) repeating the steps 1 to 5, and obtaining that the inflection point arrival time of the negative pressure wave acquired by the other sensor is 6.729 s. The arrangement distance of the two sensors is 48m, the leakage position of the pipeline is positioned by using a traditional negative pressure wave method, and the positioning error is only 0.5 m. To verify the reliability of the method, a total of 40 sets of tests were carried outThe average positioning error is 1.1m, which shows that the method can effectively improve the identification precision of the inflection point of the negative pressure wave.
Claims (1)
1. A negative pressure wave inflection point identification method based on linear fitting is characterized by comprising the following steps:
step 1: carrying out denoising processing on a negative pressure wave signal generated by pipeline leakage and acquired by a sensor;
step 2: selecting P time points and corresponding data values of the denoising signal stationary section obtained by the processing in the step 1 for linear fitting to obtain a straight line L1＝a1t+b1；
And step 3: averaging the data values corresponding to the P selected time points, and setting the data values as a leakage threshold S;
and 4, step 4: sequentially comparing data values of all points in all data of the negative pressure wave signal with S according to the sequence of the corresponding time from small to large; when the data values corresponding to the N continuous time points are lower than the set S, the pipeline leakage is considered to occur; extracting the 1 st time point of the N time points, and performing linear fitting on the next M time points and corresponding data values thereof to obtain a straight line L2＝a2t+b2；
And 5: solving two straight lines L1And L2The intersection point of the two points is the inflection point of the negative pressure wave, and the time t (b) when the sensor detects the arrival of the negative pressure wave is obtained2-b1)/(a1-a2)。
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| CN113188055B (en) * | 2021-05-31 | 2022-11-25 | 东北大学 | Pipeline leakage self-adaptive dynamic compensation positioning method based on negative pressure wave attenuation driving |
| CN113639208B (en) * | 2021-07-16 | 2022-12-06 | 汕头大学 | Negative pressure wave signal inflection point positioning method and system based on extreme approximation |
| CN113933002A (en) * | 2021-08-12 | 2022-01-14 | 吉林大学 | Method for identifying leakage point of long-distance large-scale water delivery pressure pipeline hydrostatic test |
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