| As the main transportation tool of energy materials such as oil and natural gas,with the massive construction of pipeline network,leakage accidents will inevitably occur due to aging and wear,theft,geological disasters,pipeline corrosion and other reasons,which will have an irreversible impact on economic security,environmental security,ecological security and so on.Therefore,real-time monitoring and alarm of pipeline leakage has become particularly important.At present,the pipeline leakage monitoring methods include negative pressure wave method,leakage detection cable method,mass balance method and acoustic detection method,but these methods still have the problems of false alarm signal,poor positioning accuracy and unsuitable for small-scale leakage.As a new pipeline leakage monitoring method in recent years,the distributed optical fiber monitoring method has the advantages of strong anti electromagnetic interference ability,good insulation,corrosion resistance and high voltage resistance,and can realize longdistance detection.When laying the pipeline,the optical cable can be arranged on the pipeline to realize the rapid and accurate positioning and alarm of the pipeline leakage point.Therefore,in this thesis,the distributed optical fiber vibration sensing system is used for pipeline leakage monitoring.The main research contents of this thesis are as follows:(1)The distributed optical fiber vibration sensing system is studied theoretically by phase sensitive photosensitive time-domain reflection technology.The factors affecting the spatial resolution of the distributed optical fiber vibration sensing system are analyzed.According to the spatial resolution of the system,a multi-dimensional spatial data fusion algorithm is proposed to reduce the noise of the leakage signal.(2)The components of the distributed optical fiber vibration sensing system are introduced in detail,including the optical path part and the acquisition part of the system.The selection and test of the optical path devices and the simulation analysis of the acquisition module are carried out respectively.Several key performance indexes of the distributed optical fiber vibration sensing system are tested,and the sensitivity of the optical cable used in the leakage pipeline is tested and analyzed.The results show that the optical cable is sensitive to signals below 180 Hz,and its maximum sensitivity is-153.69 dB(rad/μPa).(3)A pipeline leakage experimental platform is built to monitor the pipeline vibration caused by pipeline leakage in real time.Through the experimental platform,the single point leakage and multi-point leakage of the pipeline are tested,and the distributed optical fiber vibration monitoring system is used to record the pipeline leakage data.The multidimensional spatial data fusion algorithm is used to denoise the collected leakage signal,and compared with other denoising methods.The experimental results show that after filter filtering,wavelet denoising and multi-dimensional spatial data fusion algorithm denoising,the signal-to-noise ratio is improved by about 4.4dB,3.18 dB,3.2dB and5.35 dB respectively,among which the signal-to-noise ratio is improved the most after multi-dimensional spatial data fusion algorithm.Finally,the alarm rate of the data processed by the multi-dimensional data fusion algorithm is counted.The maximum single point leakage alarm rate is increased by 19.53%,and the multi-point leakage alarm rate is increased by 2.29%.Therefore,the multi-dimensional spatial data fusion algorithm can realize the monitoring of single point leakage and multi-point leakage,and can effectively distinguish the leakage signal from the non leakage signal,and finally improve the alarm rate of the pipeline leakage monitoring system. |
