大型变电站接地网接地电阻短距测量方法研究

发布时间：2018-04-25 20:29

本文选题：接地电阻 + 短距测量　；参考：《郑州大学》2017年硕士论文

【摘要】：随着电力行业的发展,特高压输电技术的应用日益广泛,超特高电压变电站的数量也越来越多,其接地网尺寸与之前相比显著增大。接地网的接地性能关系着电力系统的安全可靠运行。接地电阻是衡量接地系统电气性能的重要指标,在发、变电站投运前或运行一段时间后都要对其接地电阻进行测量。目前我国常用的接地电阻测量方法主要分为传统长距法和基于电位补偿理论的短距法。其中传统长距法测量引线长度需达到4~5倍接地网对角线长度,工作量较大;而基于电位补偿理论的短距法则需要根据具体地网结构来计算补偿点位置。对于实际工程中存在的设计图纸缺失的大尺寸接地网,两种方法都不适用。因此,开发研制普遍适用的接地电阻短距测量新方法至关重要。本文在深入分析传统方法测量原理的基础上,提出一种普遍适用的接地电阻短距测量新方法。首先建立了基于薄壳理论的大型接地装置有限元模型,针对有限元方法在处理大型接地网问题时剖分困难、计算量大的缺点,在建模过程中引入薄壳理论,将接地导体等效为具有一定虚拟厚度的金属薄壳,并在处理无穷大求解区域问题时引入了空间几何坐标变换,在保证计算精度的前提下大大减小了计算量,通过与文献实测结果进行对比验证了本文模型的有效性;而后基于本文所建模型分析不同结构土壤中不同形状、结构和尺寸接地网附近的地表电位分布规律,确定了采用半球型接地极模型或平板接地极模型计算接地网的远区电位时的适用范围;而后据此提出采用等效接地极模型计算电压极处的电位,并以此为参考电位,结合实测接地网与电压极间电压值来计算接地电阻的短距测量方法;最后采用本文方法测量实际接地网的接地电阻,通过与0.618法进行对比验证了本文方法的有效性。结果表明:本文方法适用于复杂土壤结构以及接地网设计图纸缺失的情况;采用半球型接地极作为计算模型时,测量引线长度缩短至2D;采用平板接地极作为计算模型时,测量引线长度缩短至1D;此外,采用本文方法测量时电压引线和电流引线可沿不同路径布置,若地形允许可沿反方向布置测量引线,此时可有效消除引线间互感。
[Abstract]:With the development of power industry, UHV transmission technology is widely used, and the number of UHV substations is increasing. The grounding performance of grounding grid is related to the safe and reliable operation of power system. Grounding resistance is an important index to measure the electrical performance of grounding system. It is necessary to measure the grounding resistance before the substation is put into operation or after running for a period of time. At present, the commonly used grounding resistance measurement methods in China mainly include the traditional long distance method and the short distance method based on the potential compensation theory. The traditional method of measuring lead length needs to reach 4 ~ 5 times the diagonal length of grounding grid, and the short distance rule based on potential compensation theory needs to calculate the position of compensation point according to the concrete ground net structure. Neither of the two methods is applicable to the large scale grounding grid which is missing from the design drawings in practical engineering. Therefore, it is very important to develop a new method for measuring earthing resistance in short distance. Based on the analysis of the traditional measuring principle, a new method for measuring the short distance of grounding resistance is proposed in this paper. Firstly, the finite element model of large earthing device based on thin shell theory is established. Aiming at the disadvantage of finite element method in dealing with the problem of large grounding grid, the thin shell theory is introduced in the process of modeling. The grounding conductor is equivalent to a thin metal shell with a certain virtual thickness, and the spatial geometric coordinate transformation is introduced in the process of solving the problem of infinite region, which greatly reduces the calculation amount on the premise of guaranteeing the calculation accuracy. The validity of the model is verified by comparing with the measured results in the literature, and then the distribution law of surface potential near the grounding grid with different shapes, structures and sizes is analyzed based on the model built in this paper. The range of application of the hemispherical earth electrode model or the plate earth pole model for calculating the far area potential of the grounding grid is determined, and then the equivalent earth electrode model is proposed to calculate the potential at the voltage pole, which is used as the reference potential. Combined with the measured voltage between the grounding grid and the voltage pole to calculate the earthing resistance of the short-distance measurement method. Finally, the method is used to measure the grounding resistance of the actual grounding grid, and the effectiveness of this method is verified by comparison with the 0.618 method. The results show that this method is suitable for complex soil structure and the missing design drawings of grounding grid, when the hemispherical earth pole is used as the calculation model, the length of the measuring lead is shortened to 2D; when the plate earth pole is used as the calculation model, the length of the measuring lead is reduced to 2D. The length of the measuring lead can be shortened to 1D, in addition, the voltage and current leads can be arranged along different paths when the method is used in this paper, and the mutual inductance between the leads can be effectively eliminated if the topography permits the arrangement of the measuring leads in the opposite direction.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM862;TM63;TM934.1

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