天然气长输管道泄漏点的检测与定位方法研究

【作者】 毛海杰；

【导师】 陈希平；

【作者基本信息】 兰州理工大学 ， 控制理论与控制工程， 2004， 硕士

【摘要】 作为五大运输行业之一的管道运输系统，以其环保、经济、快捷等优点，在国民经济中的地位越来越为突出。随着我国西部开发战略的实施，必将有大量的油气管道投入建设和运行。然而近些年来，由于管道的自然寿命和人为因素等的影响，管道泄漏事故频繁发生，不仅造成大量物质损失和环境污染，还带来了重大的人身伤亡事故。及时发现管道泄漏和精确确定泄漏点位置对于减少损失、维护管道安全运行显得十分重要。为将泄漏事故造成的各种危害减少到最小，需要研究泄漏检测技术，以达到更高的泄漏检测灵敏度和更准确的泄漏点定位精度。 鉴于天然气长输管道的模型受到流体特性、地势状况及管道自身的特性等诸多复杂因素的制约，难于建立其精确的数学模型，新铺设的输气管网均已配有SCADA系统，对现场各类数据有了丰富的储备等因素，同时结合我国管道输送的实际情况，并借鉴目前国际上各种泄漏检测与定位的先进方法，针对天然气长输管线泄漏故障的特点，本文提出了基于小波分析和负压波相结合的检测泄漏与定位技术。其中，主要进行了以下几方面的工作： 针对泄漏产生的负压波在管道中的传播速度受媒介的密度、压力、比热及材质等因素的影响，而非声波在空气中传播的速度，本文利用能量守恒原理，对其进行了修正；考虑到管内气体流速对压力波速的影响，对原始的负压波定位公式进行了一定程度的改进，并在利用定位公式进行泄漏点定位时采用逐步迭代逼近算法，提高了系统的定位精度； 利用小波变换的多分辨率分解和重构技术，对采集到的管道发生泄漏时产生的负压波信号进行了降噪处理；并利用小波变换技术对信号奇异点的快速、准确的识别能力，对经上述消噪后的负压波信号进行了奇异点捕捉，精确捕捉的结果提高了定位公式中上下游站点采集到的负压波奇异点的时间差△t的精度，从而进一步提高了定位的精度； 考虑到小波变换是一种基波可变的信号分析工具，也就是说，不同的小波基波对信号分析的结果将有很大差别，这势必影响最终的处理结果，因此，我们又对比分析了本课题中小波基及尺度的选择问题，依据规则性系数相似性原理对母小波的选择进行了探索性研究； 最后，还提出了基于SCADA的泄漏检测与定位系统的软件开发构想及系统的嵌入方案。更多还原

【Abstract】 As one of the five main transport industries, long pipeline delivery system and its safe operation are of great significant importance due to the serious consequences that may result from different reasons. Leaks from the pipelines can not only lead to a great deal of product losses and environment pollution, but also cause many people hurt, even to die. In recently, with some artificial destruction such as stealing natural gas and so on, leakage cases became more and more seriously. So it’s very important and very necessary to find the leak and locate it on time in order to reduce the losses and keep the system operate normally.With the "West Development" project carried on. the natural gas pipeline in our country will get into another high tide. Plenty of pipelines will be launched into building and running. In order to reduce the harm caused by leakage to the least and to get to higher leak sensitivity and location accuracy, it’s very necessary to research the leak detection and location technique.Seeing that the math model of natural gas pipeline is limited to the fluid character, terrain status, pipeline itself character as well as some complicated restriction, it’s difficult to establish the accurate mathematic model. On the other hand, the SCADA systems have been installed in the new laid natural gas pipeline. Lots of local date can be easily obtained. At the same time, combining with the actual condition of delivery pipeline of our country and some prevalent leak detection and location methods, this paper raised a method, which is based on wavelet analysis and negative- pressure-wave to detect and locate the leakage. Jobs in the paper are as follows:As affected by gas density, pressure, specific heat and pipe material, the velocity of negative-pressure-wave improved depending on the energy conservation. At one time, taking the affection of velocity of gas flow, the location formula was modified in some degree.When locating the leaks with location formula, the iterative approach algorithm was adopted as a new method to increase the location accuracy level of system.Multi-scale decomposition and reconstruction of wavelet transform is utilized to filter the noise of negative-pressure-wave, which was brought by leakage. With the capacity to detect the signal singularity fast and accurately, wavelet transform was used to catch the break point of pressure signal. The work improved the accuracy of At in location formula, accordingly improved the location accuracy.Wavelet is a suitable tool for signal analysis. The distinct character is that the mother-wavelet is of optional. That means choosing different mother-wavelet will get different analysis result. So we studied how to choose mother-wavelet and its scale for signal singularity detection. The method is to choose a wavelet by regularities of the wavelet and the signal.Finally, a plan, which bases on SCADA system for inspection and detection of natural gas leakage, is proposed in the article.更多还原