The Design Of Pipeline Destroy Prewarning System Based On OFDR Technique And Signals Processing Methods Research

Pipeline transmission approach is currently the main way to transport oil and gas production. However, the third-party damage has become the most important threat to the safe operation of oil and gas pipeline. It not only affects the steady and reliable supply of important energy products, but also poses a great threat to the safety of the country, people’s lives and property as well as the environment. Current pipeline detection methods rely mainly on pipeline operating parameters and pipe-wall state detection technology, which is effective to pipeline leak detection to a certain degree, but produces poor results in the detection of the growing third party pipeline damages since it only gives an alarm only after the leakage accident. It is impossible to retrieve losses of energy waste, pollution and other direct or indirect caused by leakage. Therefore, the need for pipeline safety inspection techniques with an early warning and detection against the third party damage is urgent so that alarm information can be given to the relevant departments when the third-party damage is caused and timely measures can be taken by those departments to prevent third-party damage activIn connection with the characteristics of oil and gas pipeline and third-party sabotage activities, this paper prop ities. Hence, the occurrence of pipeline leakage accidents can be avoided effectively.oses an early warning and detection program for the third-party sabotage activities based on OFDR technique and fiber Michelson interferometer principles. A pipeline damage prevention, early warning and detection system is designed based on the detection program and detailed analysis and research are conducted on the working principle of every components of the system and its design methods.The detection system of the program adopts ordinary single-mode fiber as distributed sensors, which are laid near the pipeline along the transmission route and enable non-blind area distributed detection of the long-distance oil and gas pipeline. A large-scale quasi-distributed fiber Bragg grating array is implanted in the sensor fiber as multiple reflectors, which forms a fiber Michelson interferometer detection system that has a positioning capability to external perturbations in association with the reflector set in the reference arm of the fiber-optic Michelson interferometer. Being different from the application of conventional optical fiber grating, the fiber Bragg grating in this system does not function as a sensor but as a reflector which reflects light. Therefore, the parameters of the fiber grating have a specific requirement. This paper analyses the selection principles of the fiber grating parameters according to the system principles and studies methods to produce it. Then fiber Bragg grating which meets the requirements of the system is produced and the sensing fiber production and fiber processing are completed. Sensor cable along the pipeline picks up the vibration signals sent out by the third-party sabotage activities, then detects the signals based on OFDR optical heterodyne detection method. It further designs the signal transfer and signal conditioning circuit according to the characteristics of the detected signals and carries out the digital collection of the detection signals through the use of capture card. Specially designed computer software is used to analyze and process the collected signal so that disturbance incidents alongside the pipeline is detected and located using signal power spectrum analysis and vibration information caused by disturbance events is retrieved by the application of the phase-locked loop technology which provide basis for the further identification of the type of disturbance events as well as the determination of the nature of disturbance events.Currently the designed sensor optical cable has been laid in Cangzhou-Dezhou section of the Gang-Zao (Dagang, Tianjin to Zaozhuang, Shandong) oil pipeline. It has been proved to meet the system requirements after several field tests. As the initial results, the current system prototype has already begun to function and laboratory simulation and field test results show that the system solutions are feasible with its functions to be further improved.