直流输电系统接地电流对管道腐蚀机理研究

发布时间：2018-02-25 04:06

本文关键词： 燃气管道接地电流杂散电流腐蚀干扰防护　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着国家经济发展对能源需求的日益增加,高压输送电系统和天然气管道的建设正在高速发展。由于空间的限制,高压输送电系统可能影响到燃气管道的安全。其原因在于高压输送电系统在单极运行时会产生非常大的接地电流,形成干扰埋地管道的杂散电流,导致管道发生腐蚀、管道的附属设备及设施受到干扰和损坏。为避免因管道腐蚀引发灾难性事故,保障管道安全运营,开展接地电流对管道腐蚀的机理和防护措施研究具有重要意义。由于杂散电流腐蚀其本质上是电化学腐蚀,本文首先开展直流电流对埋地钢质管道的电化学腐蚀实验研究,探究直流电流产生的地电场和电流密度对管道腐蚀的影响规律。在此基础上,开展高压直流接地极周边地区的电场分布与电流密度的数值模拟研究,以期揭示接地电流对管道腐蚀的影响规律并提出对应的防护措施。论文主要开展了以下几个方面研究工作:(1)分析了高压直流输电系统接地极产生接地电流的原因及其对管道安全的影响。主要阐述了直流输送电线路运行方式及其非正常工作状态单极运行方式下,大电流注入大地时对油气站场、阀室、管道及相关附属设施的干扰影响,引起直流地电场,以及地电流对油气管道电化学腐蚀,对站场、阀室内阴极保护设备和设施的影响,并结合工程案例分析了接地电流对输气管道的干扰情况。(2)开展了直流杂散电流对天然气埋地钢质管道的电化学腐蚀实验研究。通过电化学腐蚀实验,重点研究了直流电场分布规律、直流电流密度对钢质试件的腐蚀影响和作用机理。通过对极化曲线、交流阻抗谱、腐蚀形貌特征以及腐蚀速率的分析表明,随着外加电流和直流电流密度的增大,工作电极的腐蚀速率增加。(3)开展了接地极对埋地管道腐蚀的数值模拟分析。结合实际工程,分析了接地极周围电场分布以及接地极类型(阴极、阳极接地)、接地极与管道的距离对地电流密度的影响。研究表明,随着接地电流的增大,管道的最小电位逐渐减小,管道的最大电流成线性增大;当直流接地极单极运行时管地电位远远超出相关标准中的限值。(4)开展了直流干扰区管道的杂散电流防护措施研究。结合实际工程,提出了直流干扰下的一般性原则和具体防护措施,并重点研究了隔离措施对杂散电流干扰管道的防护作用规律。研究表明,当接地极为阳极运行时隔离措施会引起较大的直流干扰,而接地极为阴极运行时则相反;在分段隔离区域两段采取阴极保护能够有效弥补隔离措施的不足。总之,论文通过理论研究和实验数值模拟,针对高压输电系统接地极对燃气管道的杂散电流腐蚀影响规律,探索了接地电流引起的地电场分布状况和影响范围,提出了输气管道工程对接地极干扰防护措施。研究成果为缓减经济发达地区共用走廊内高压i输电系统与埋地管道之间的矛盾,有效避免杂散电流引起的电化学腐蚀,确保管线运行安全提供技术指导。
[Abstract]:With the development of the national economy increasing demand for energy, power transmission system and the construction of high pressure natural gas pipeline is developing rapidly. Due to the limited space, high-voltage transmission system may affect the gas pipeline safety. The reason is that the high voltage power transmission system will have a very large grounding current in monopolar operation, the formation of stray current interference of buried pipeline, resulting in pipeline corrosion, ancillary equipment and facilities of the pipeline is disturbed or damaged. To avoid pipeline corrosion caused catastrophic accidents, ensuring the safety of the pipeline operation, is of great significance to carry out ground flow of pipeline corrosion mechanism and protection measures research. Because of the stray current corrosion is essentially electrochemical this paper carried out experimental study on corrosion, electrochemical corrosion current of buried steel pipeline, to explore the generation of DC ground electric field and current density Influence of pipeline corrosion. Based on the numerical simulation of electric field distribution and current density of high voltage DC grounding of the surrounding area, in order to reveal the regularity of ground current effect on pipeline corrosion and puts forward corresponding preventive measures. The paper mainly carried out the following research work: (1) grounding generation the reason of grounding current of high voltage DC transmission system and its influence on the safety of pipelines are discussed. The DC power transmission line operating mode and non normal working state of monopole operation mode, the oil and gas station, valve chamber current injected into the earth, interference of pipelines and related ancillary facilities, caused by the DC electric field. And the current electrochemical on oil and gas pipeline corrosion, the influence of valve chamber station, cathodic protection equipment and facilities, and combined with the engineering case analysis of grounding current on the gas pipeline Interference. (2) carried out experimental study on electrochemical corrosion of stray current on buried steel gas pipeline. The electrochemical corrosion experiment, focusing on the DC electric field distribution, the effect and mechanism of corrosion test of DC current density of the steel. The polarization curves, AC impedance, corrosion characteristics and analysis the corrosion rate showed that with an increase of current and DC current density, the corrosion rate of working electrode increased. (3) carried out a numerical simulation analysis of grounding electrode on buried pipeline corrosion. Combined with the practical engineering, analysis of ground electric field distribution around the electrode and the electrode type (cathode, anode grounding, grounding effect) the ends of the earth and the distance to the ground pipeline current density. The results show that with the increase of ground current, the minimum potential pipeline decreases, the maximum current pipeline linearly when DC; Grounding monopole operation tube ground potential is far beyond the limits of the relevant standards. (4) carried out research on the stray current protection measures DC interference area pipeline. Combined with the actual project, put forward the general principles under DC interference and specific protection measures, and focus on the protection effect of isolation measures of stray current interference the pipeline. The results show that when the grounding electrode as the anode operation isolation measures will cause DC interference, and the grounding electrode as cathode when running the opposite; in the two section of regional sectionalizing cathodic protection can effectively compensate for the lack of isolation measures. In a word, through the research and experiment of numerical simulation theory for high voltage transmission the grounding system of stray current corrosion of gas pipeline, explores the grounding current caused by the electric field distribution and the influence scope, proposed gas pipeline engineering docking The research results are to mitigate the contradiction between the high voltage I transmission system and buried pipelines in the shared corridor, and effectively avoid the electrochemical corrosion caused by stray current, and provide technical guidance for ensuring the safety of pipeline operation.

【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE988.2

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