As we all know, the pipeline transport has a smooth and continuous, safe, transport volume, easy quality assurance, small material loss and small footprint, low freight, has become the preferred mode of oil transportation. However, the gradual aging of pipelines, corrosion of various media, and vandalism can cause pipeline leakage, seriously threatening the safety of pipelines and the surrounding natural environment, as well as incalculable economic losses. At present, there are many methods for detecting and locating leaks in traditional oil pipelines at home and abroad, including:
Hardware-based detection methods, such as artificial patrol line, "pipe pig", acoustic emission technology and light detection, cable detection and GPS detection;
Software-based detection methods such as negative pressure wave method, pressure gradient method, etc.
Although there are many methods, the distance that acoustic emission signals travel on oil pipelines is extremely limited, which is not conducive to long-distance detection. In particular, the high requirements and high standards for precise timeliness and precise positioning of leaks are still unsatisfactory. In the face of these new challenges in the safe operation of these oil production and pipelines, the application of technical support systems to the monitoring of oil pipeline leakage has emerged. Among them, the distributed multi-point synchronous data acquisition device positioning technology triggered by GPS satellite signals is a new technical support system. This new technology guarantee system is actually composed of virtual instrument technology, synchronous sampling technology of the whole network, and distributed multi-point synchronous data acquisition technology triggered based on GPS satellite signals. These three are closely linked and support each other.
This paper takes the application of multi-point synchronous data acquisition technology triggered by GPS satellite signal based on virtual instrument graphics software LabVIEW in oil production and safe operation of pipelines as an example to discuss the application of new technology protection system in oil pipeline leakage monitoring.
Virtual Instrument Graphics Software LabVIEW Technology Concept
Today, virtual instrument technology has been in-depth and popular. Virtual Instrument Technology combines efficient graphics software, modular I/O, and an extensible platform. With virtual instrument technology, engineers have reduced development time and reduced design costs by designing higher quality products.
LabVIEW, the graphics software, is fundamental to the flexibility and convenience of virtual instruments. LabVIEW is an important part of the virtual instrument because it provides an easy-to-use application development environment designed specifically for engineers and scientists. LabVIEW provides many powerful features that make it easy to connect with a lot of hardware and software. Easy to use and other features provide the flexibility required for a virtual instrument software development environment, resulting in a user-defined interface and user-defined application functionality. One of the many powerful features provided by LabVIEW is the graphical programming environment. With LabVIEW, engineers can create custom virtual instruments by creating a graphical user interface on a computer screen; through the computer screen, they can operate the instrument program, control the selected hardware, analyze the acquired data, and display the results; you can use the knob, Buttons, Dials, and Charts Customize the LabVIEW user interface, or front panel, to emulate the control panels of traditional instruments, create custom test panels, or visually represent process controls and operations.
GPS-based multiple simultaneous testing internet <br> <br> sampling synchronous sampling points synchronous sampling unit, and sub-sampling synchronization based on the GPS multi-synchronous sampling technique to test three types of network. In this paper, we will focus on the technology of GPS-based multi-point synchronous sampling test network.
Synchronous sampling is also called tracking sampling. That is, in order to keep the sampling frequency fs always constant with the frequency f1 of the actual operation of the system, N=fs/f1, the sampling frequency must be adjusted in real time according to the frequency of system operation. The technical guarantee implemented by this kind of synchronous sampling method can be achieved by using hardware frequency measuring equipment or software to calculate the frequency. The large-scale test network for multi-point simultaneous sampling includes a GPS-based multi-point synchronous sampling test network technology. One of the characteristics of this kind of test network is that the spatial distribution can be as large as tens of kilometers, and the second is that the number of measurement points can be as many as a thousand. There are many situations in this kind of test network that require synchronous sampling of each test point, such as pipeline leakage monitoring, grid surge testing, seismic waves, wind speed measurement, etc., and hundreds of measurement points need to be strictly sampled at the same time. signal.
The core of multi-point synchronous sampling large test network is based on GPS synchronous sampling technology. This is the first explanation of the GPS synchronous sampling technology concept.
An oscillator composed of a high-precision crystal oscillator can generate a clock signal that satisfies the sampling rate after frequency division. It synchronizes with the GPS pulse per second (PPs) signal every 15 seconds to ensure that the oscillator outputs the leading edge of the pulse signal and GPS. Time synchronization. Since each device uses the synchronized clock signal output by the oscillator as the sampling pulse output to control the respective data acquisition, the sampling is synchronized. The GPS receiver transmits the time information to the data acquisition device via a standard serial port, which is used to give the sampled data a “time tag†for data transmission and processing such as temperature (T), flow (F), and the like of the pipeline. Therefore, the use of GPS to achieve synchronous sampling, can ensure that each test point of the data sampling high-precision synchronization, the maximum synchronization error does not exceed lS, which is unmatched by other synchronization methods.
For industries that involve time information, such as digital communications, cable television networks, and power systems, it is also possible to choose convenient and inexpensive GPS OEM boards. It has two output ports, one is an lpps second pulse port that outputs one pulse per second, and the other is an RS232 interface that outputs GPS message information. After the GPS OEM board receives the satellite message with valid time information, the synchronization error of the output second pulse signal and the CPS time is within 50 ns, and the synchronization error with UTC is within 1 μs. Applying it to a system that requires precise timing, a time-synchronized system with higher accuracy can be obtained. Therefore, based on GPS synchronous sampling technology will be widely used in oil pipeline leakage monitoring.
The actual application of the GPS satellite new multi-point synchronous data acquisition device architecture includes a computer, a GPS satellite receiver and a measured object, and is characterized in that: a PCI bus data acquisition card is provided on the computer, and the second pulse signal of the GPS satellite receiver is The PCI bus data acquisition card is connected to the digital trigger channel. The standard time signal of the GPS satellite is connected to the computer serial port. The measured object is connected to the PCI bus data acquisition card analog input channel, and the test data is output through the computer network. Therefore, a distributed data acquisition device based on GPS synchronous sampling technology is particularly suitable for applications where long-range precision positioning of oil pipeline leakage monitoring is required.
The PCI bus is a sturdy, modular structure that combines the PCI electrical specification with the Eurocard package for the extension of the industrial computer specification. CompactPCI defines a rugged, industrial-strength PCI bus architecture that provides excellent mechanical integrity with hardware modules that are easy to handle. Therefore, PXI products have higher level and more stringent environmental consistency indicators, which meet the extreme conditions of vibration, impact, temperature, and humidity in industrial environments.
New multi-point distributed synchronous data acquisition device
One of the important functions of the distributed synchronous data acquisition and monitoring system is to realize synchronous data acquisition and synchronous monitoring of the status. The key problem in realizing this system is to improve the synchronization accuracy of the working time of the synchronous data acquisition card.
Synchronous sampling of synchronous data acquisition card or approximate synchronous sampling of non-synchronized data acquisition card can achieve synchronous data acquisition of the test unit, and it can easily implement data acquisition in multiple locations distributed in different regions for strict time synchronization. Then, how can the multi-point synchronous sampling technology based on the virtual instrument graphics software LabVIEW be used in the technical support system for oil production and safe operation of pipelines (ie, for oil pipeline leakage monitoring applications)?
1, the design of pipeline leakage monitoring
Install computer or other data acquisition devices at substations along the pipeline, collect pressure, temperature, and flow signals from the pipeline, transmit it to the master control host through computer networks, wireless public networks, radios, and other media. Analyzes and manages, finds the alarm and locates the leak when discovering leak.
The oil pipeline leakage monitoring system requires that each substation computer strictly and synchronously perform data acquisition. At the same time, the sampling data at the same time reaches the master host computer for analysis and positioning to determine the location of the leakage point. However, due to the current level of network technology, this is almost impossible to do. In order to make up for the difference in data transmission time caused by the network environment, the sampling data can be transmitted to the host computer with the “time stampâ€, and the sampling data can be “aligned†according to the sampling time when locating the leak point. The software-based pressure gradient method based on the wood trimming technique can be used to locate the pipeline leakage, and the time error Δt of the sampling data at the upstream and downstream of the pipeline reaching the control center can be obtained. According to the actual calculation of the formula, every 1s of data synchronization error will cause a positioning error of about 500m, while the use of GPS satellite signal trigger data acquisition technology will reduce the time synchronization error of the data to 3μs, and the positioning error caused by the data transmission time error will decrease. Within 3m.
It should be pointed out that the sampling rate of the analog sampling temperature (T) and flow rate (F) set by each synchronous acquisition card is 1000S/s, and the sampling number is 500S, that is, the sampling time is 500ms. The master control host program receives signals from two ports upstream and downstream, respectively, from two ports.
2, multi-point synchronous sampling technology
Oil pipeline leakage monitoring includes three technologies, including the DAQmx program triggered by GPS satellite signals, and the substation program structure and master station program structure. This section focuses on the application of the DAQmx program triggered by GPS satellite signals. Specifically on what is the DAQmx program, a new generation of DAQ driver software and LabVIEW contains two device driver applications for research.
DAQ is an abbreviation of English Data Acquisition. Data acquisition (DAQ) refers to the process of measuring electrical or physical phenomena such as voltage, current, temperature, pressure, sound, and coded data. Its DAQ applications include measurement and visualization, data logging, control, automated testing, and monitoring.
DAQmx is a new generation of DAQ driver software development (for example, NI Corporation), which can help create, test, and use high-performance measurement applications more quickly. Its DAQmx measurement service software, in addition to the basic functions of data acquisition (DAQ) drive, also has higher work efficiency and more performance advantages, so it can be widely used in the field of virtual instrument technology and data acquisition based on computer technology. . The DAQmx Measurement Services software works with all DAQmx-supported DAQ boards and offers the following features: Unified, simple programming interface for all multifunction data acquisition (DAQ) hardware, programming of analog inputs, analog outputs, digital I/O, and counter programs Using multi-threaded and optimized single-point I/O function, the operating speed can be increased by 1000 times; in the various programming environments such as LabVIEW, LabWindows/CVI, Visual Studio.NET, and C/C++, the same VI program or Functions; use Measurement & Automation Explorer (MAX), Data Acquisition Assistant (DAQAssistant), and VILogger data logging software to save a lot of system configuration, development and data recording time.
LabVIEW includes two device drivers - traditional DAQ and DAQmx. Based on these two drivers, two independent data acquisition systems are formed. In both data acquisition systems, the existing data acquisition hardware should be considered first. The new M Series data acquisition card can use DAQmx. Therefore, the LabVIEW graphics software uses the DAQmx GPS satellite signal to trigger the sampling process. The VI (virtual instrument-virtual instrument) in the program is as follows:
DAQmxCreateTask: create data collection tasks;
DAQmxCreateChannel: Create a data acquisition channel. Set sampling device and its physical channel, signal connection method, signal limit setting, channel name, unit, conversion and other parameters;
DAQmxTiming: timing. Set the number of samples, sampling rate and sampling method;
DAQmxTrigger: Trigger. Set the trigger type to the rising edge of the digital signal edge (Rising). The trigger source (source) is PF10. When using the PCI-6221 data acquisition L, the second pulse signal of the GPS satellite signal receiver is connected to the 1l pin of the CB68 terminal block;
DAQmxControlTask: Task Control. Set to send the task (commit);
DAQmxRead: Read data. Select multi-channel multi-sampling to return a two-dimensional floating-point array instance;
DAQmxStopTask: Stop the task.
Conclusion
The new multi-point synchronous data acquisition device framework triggered by GPS satellite signals can keep the sampling pulse time error of the oil pipeline leakage monitoring and protection system within several μS, so as to make the leakage detection sensitivity and the timeliness of leakage detection. The leaked false alarm rate, etc., have greatly improved the accuracy and protection of the location and location of the fault.
Hardware-based detection methods, such as artificial patrol line, "pipe pig", acoustic emission technology and light detection, cable detection and GPS detection;
Software-based detection methods such as negative pressure wave method, pressure gradient method, etc.
Although there are many methods, the distance that acoustic emission signals travel on oil pipelines is extremely limited, which is not conducive to long-distance detection. In particular, the high requirements and high standards for precise timeliness and precise positioning of leaks are still unsatisfactory. In the face of these new challenges in the safe operation of these oil production and pipelines, the application of technical support systems to the monitoring of oil pipeline leakage has emerged. Among them, the distributed multi-point synchronous data acquisition device positioning technology triggered by GPS satellite signals is a new technical support system. This new technology guarantee system is actually composed of virtual instrument technology, synchronous sampling technology of the whole network, and distributed multi-point synchronous data acquisition technology triggered based on GPS satellite signals. These three are closely linked and support each other.
This paper takes the application of multi-point synchronous data acquisition technology triggered by GPS satellite signal based on virtual instrument graphics software LabVIEW in oil production and safe operation of pipelines as an example to discuss the application of new technology protection system in oil pipeline leakage monitoring.
Virtual Instrument Graphics Software LabVIEW Technology Concept
Today, virtual instrument technology has been in-depth and popular. Virtual Instrument Technology combines efficient graphics software, modular I/O, and an extensible platform. With virtual instrument technology, engineers have reduced development time and reduced design costs by designing higher quality products.
LabVIEW, the graphics software, is fundamental to the flexibility and convenience of virtual instruments. LabVIEW is an important part of the virtual instrument because it provides an easy-to-use application development environment designed specifically for engineers and scientists. LabVIEW provides many powerful features that make it easy to connect with a lot of hardware and software. Easy to use and other features provide the flexibility required for a virtual instrument software development environment, resulting in a user-defined interface and user-defined application functionality. One of the many powerful features provided by LabVIEW is the graphical programming environment. With LabVIEW, engineers can create custom virtual instruments by creating a graphical user interface on a computer screen; through the computer screen, they can operate the instrument program, control the selected hardware, analyze the acquired data, and display the results; you can use the knob, Buttons, Dials, and Charts Customize the LabVIEW user interface, or front panel, to emulate the control panels of traditional instruments, create custom test panels, or visually represent process controls and operations.
GPS-based multiple simultaneous testing internet <br> <br> sampling synchronous sampling points synchronous sampling unit, and sub-sampling synchronization based on the GPS multi-synchronous sampling technique to test three types of network. In this paper, we will focus on the technology of GPS-based multi-point synchronous sampling test network.
Synchronous sampling is also called tracking sampling. That is, in order to keep the sampling frequency fs always constant with the frequency f1 of the actual operation of the system, N=fs/f1, the sampling frequency must be adjusted in real time according to the frequency of system operation. The technical guarantee implemented by this kind of synchronous sampling method can be achieved by using hardware frequency measuring equipment or software to calculate the frequency. The large-scale test network for multi-point simultaneous sampling includes a GPS-based multi-point synchronous sampling test network technology. One of the characteristics of this kind of test network is that the spatial distribution can be as large as tens of kilometers, and the second is that the number of measurement points can be as many as a thousand. There are many situations in this kind of test network that require synchronous sampling of each test point, such as pipeline leakage monitoring, grid surge testing, seismic waves, wind speed measurement, etc., and hundreds of measurement points need to be strictly sampled at the same time. signal.
The core of multi-point synchronous sampling large test network is based on GPS synchronous sampling technology. This is the first explanation of the GPS synchronous sampling technology concept.
An oscillator composed of a high-precision crystal oscillator can generate a clock signal that satisfies the sampling rate after frequency division. It synchronizes with the GPS pulse per second (PPs) signal every 15 seconds to ensure that the oscillator outputs the leading edge of the pulse signal and GPS. Time synchronization. Since each device uses the synchronized clock signal output by the oscillator as the sampling pulse output to control the respective data acquisition, the sampling is synchronized. The GPS receiver transmits the time information to the data acquisition device via a standard serial port, which is used to give the sampled data a “time tag†for data transmission and processing such as temperature (T), flow (F), and the like of the pipeline. Therefore, the use of GPS to achieve synchronous sampling, can ensure that each test point of the data sampling high-precision synchronization, the maximum synchronization error does not exceed lS, which is unmatched by other synchronization methods.
For industries that involve time information, such as digital communications, cable television networks, and power systems, it is also possible to choose convenient and inexpensive GPS OEM boards. It has two output ports, one is an lpps second pulse port that outputs one pulse per second, and the other is an RS232 interface that outputs GPS message information. After the GPS OEM board receives the satellite message with valid time information, the synchronization error of the output second pulse signal and the CPS time is within 50 ns, and the synchronization error with UTC is within 1 μs. Applying it to a system that requires precise timing, a time-synchronized system with higher accuracy can be obtained. Therefore, based on GPS synchronous sampling technology will be widely used in oil pipeline leakage monitoring.
The actual application of the GPS satellite new multi-point synchronous data acquisition device architecture includes a computer, a GPS satellite receiver and a measured object, and is characterized in that: a PCI bus data acquisition card is provided on the computer, and the second pulse signal of the GPS satellite receiver is The PCI bus data acquisition card is connected to the digital trigger channel. The standard time signal of the GPS satellite is connected to the computer serial port. The measured object is connected to the PCI bus data acquisition card analog input channel, and the test data is output through the computer network. Therefore, a distributed data acquisition device based on GPS synchronous sampling technology is particularly suitable for applications where long-range precision positioning of oil pipeline leakage monitoring is required.
The PCI bus is a sturdy, modular structure that combines the PCI electrical specification with the Eurocard package for the extension of the industrial computer specification. CompactPCI defines a rugged, industrial-strength PCI bus architecture that provides excellent mechanical integrity with hardware modules that are easy to handle. Therefore, PXI products have higher level and more stringent environmental consistency indicators, which meet the extreme conditions of vibration, impact, temperature, and humidity in industrial environments.
New multi-point distributed synchronous data acquisition device
One of the important functions of the distributed synchronous data acquisition and monitoring system is to realize synchronous data acquisition and synchronous monitoring of the status. The key problem in realizing this system is to improve the synchronization accuracy of the working time of the synchronous data acquisition card.
Synchronous sampling of synchronous data acquisition card or approximate synchronous sampling of non-synchronized data acquisition card can achieve synchronous data acquisition of the test unit, and it can easily implement data acquisition in multiple locations distributed in different regions for strict time synchronization. Then, how can the multi-point synchronous sampling technology based on the virtual instrument graphics software LabVIEW be used in the technical support system for oil production and safe operation of pipelines (ie, for oil pipeline leakage monitoring applications)?
1, the design of pipeline leakage monitoring
Install computer or other data acquisition devices at substations along the pipeline, collect pressure, temperature, and flow signals from the pipeline, transmit it to the master control host through computer networks, wireless public networks, radios, and other media. Analyzes and manages, finds the alarm and locates the leak when discovering leak.
The oil pipeline leakage monitoring system requires that each substation computer strictly and synchronously perform data acquisition. At the same time, the sampling data at the same time reaches the master host computer for analysis and positioning to determine the location of the leakage point. However, due to the current level of network technology, this is almost impossible to do. In order to make up for the difference in data transmission time caused by the network environment, the sampling data can be transmitted to the host computer with the “time stampâ€, and the sampling data can be “aligned†according to the sampling time when locating the leak point. The software-based pressure gradient method based on the wood trimming technique can be used to locate the pipeline leakage, and the time error Δt of the sampling data at the upstream and downstream of the pipeline reaching the control center can be obtained. According to the actual calculation of the formula, every 1s of data synchronization error will cause a positioning error of about 500m, while the use of GPS satellite signal trigger data acquisition technology will reduce the time synchronization error of the data to 3μs, and the positioning error caused by the data transmission time error will decrease. Within 3m.
It should be pointed out that the sampling rate of the analog sampling temperature (T) and flow rate (F) set by each synchronous acquisition card is 1000S/s, and the sampling number is 500S, that is, the sampling time is 500ms. The master control host program receives signals from two ports upstream and downstream, respectively, from two ports.
2, multi-point synchronous sampling technology
Oil pipeline leakage monitoring includes three technologies, including the DAQmx program triggered by GPS satellite signals, and the substation program structure and master station program structure. This section focuses on the application of the DAQmx program triggered by GPS satellite signals. Specifically on what is the DAQmx program, a new generation of DAQ driver software and LabVIEW contains two device driver applications for research.
DAQ is an abbreviation of English Data Acquisition. Data acquisition (DAQ) refers to the process of measuring electrical or physical phenomena such as voltage, current, temperature, pressure, sound, and coded data. Its DAQ applications include measurement and visualization, data logging, control, automated testing, and monitoring.
DAQmx is a new generation of DAQ driver software development (for example, NI Corporation), which can help create, test, and use high-performance measurement applications more quickly. Its DAQmx measurement service software, in addition to the basic functions of data acquisition (DAQ) drive, also has higher work efficiency and more performance advantages, so it can be widely used in the field of virtual instrument technology and data acquisition based on computer technology. . The DAQmx Measurement Services software works with all DAQmx-supported DAQ boards and offers the following features: Unified, simple programming interface for all multifunction data acquisition (DAQ) hardware, programming of analog inputs, analog outputs, digital I/O, and counter programs Using multi-threaded and optimized single-point I/O function, the operating speed can be increased by 1000 times; in the various programming environments such as LabVIEW, LabWindows/CVI, Visual Studio.NET, and C/C++, the same VI program or Functions; use Measurement & Automation Explorer (MAX), Data Acquisition Assistant (DAQAssistant), and VILogger data logging software to save a lot of system configuration, development and data recording time.
LabVIEW includes two device drivers - traditional DAQ and DAQmx. Based on these two drivers, two independent data acquisition systems are formed. In both data acquisition systems, the existing data acquisition hardware should be considered first. The new M Series data acquisition card can use DAQmx. Therefore, the LabVIEW graphics software uses the DAQmx GPS satellite signal to trigger the sampling process. The VI (virtual instrument-virtual instrument) in the program is as follows:
DAQmxCreateTask: create data collection tasks;
DAQmxCreateChannel: Create a data acquisition channel. Set sampling device and its physical channel, signal connection method, signal limit setting, channel name, unit, conversion and other parameters;
DAQmxTiming: timing. Set the number of samples, sampling rate and sampling method;
DAQmxTrigger: Trigger. Set the trigger type to the rising edge of the digital signal edge (Rising). The trigger source (source) is PF10. When using the PCI-6221 data acquisition L, the second pulse signal of the GPS satellite signal receiver is connected to the 1l pin of the CB68 terminal block;
DAQmxControlTask: Task Control. Set to send the task (commit);
DAQmxRead: Read data. Select multi-channel multi-sampling to return a two-dimensional floating-point array instance;
DAQmxStopTask: Stop the task.
Conclusion
The new multi-point synchronous data acquisition device framework triggered by GPS satellite signals can keep the sampling pulse time error of the oil pipeline leakage monitoring and protection system within several μS, so as to make the leakage detection sensitivity and the timeliness of leakage detection. The leaked false alarm rate, etc., have greatly improved the accuracy and protection of the location and location of the fault.
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