考虑土壤电离特性时变电站接地网的暂态特性  

Transient Characteristics of Grounding Grid of Substation When Considering the Soil Ionization

作　　者：陈有军[1] 王丰华[1] 金之俭[1] 吴剑敏[2] 

机构地区：[1]上海交通大学电气工程系,上海200240 [2]上海市电力公司超高压输变电公司,上海200063

出　　处：《高电压技术》2010年第3期692-698,共7页High Voltage Engineering

基　　金：国家重点基础研究发展计划(973计划)(2005cb221500)~~

摘　　要：当接地网遭受雷击时,较大的泄漏电流产生的电场可能会使接地网导体周围的土壤发生电离,使得接地网参数发生变化,此外,雷电流不像工频电流那样具有恒定的频率和幅值,因此常用的仿真软件难以模拟该复杂的暂态过程。为了准确地计算出变电站接地网的雷电冲击暂态特性,在考虑土壤电离特性的基础上,建立了较为完善的雷电流冲击作用下的接地网暂态分析模型,即全面考虑了接地网的自身电阻、电感以及对地电容作用,并采用快速傅立叶(反)变换,将频域和时域分析方法相结合,对考虑土壤电离时接地网的暂态特性进行了分析。计算结果表明:雷电冲击接地网时,土壤临界击穿场强越小,电流注入点电位就越小,反之亦然;考虑电离时接地网最远两点间的电位差有所下降;雷电流从边角注入时接地网散流能力差,土壤电离更严重;土壤电阻率与土壤电离程度密切相关。When the grounding grid is struck by the lightning stroke,the large electric field generated by leakage current may lead to soil ionization around the grounding grid which makes the variations of the grounding grid parameters.Moreover,the lightning current does not have a constant frequency and amplitude just as the power frequency current.Therefore,it is difficult for the commonly used simulation software to simulate the complicated transient process.In order to accurately calculate the impact of the lightning transient characteristics of the grounding grid,a comprehensive analysis model that the lightning current strikes the grounding grid is established when considering the soil ionization.That is to say,the self resistors,inductors and capacitances of the grounding grid are all considered in the proposed model.By virtue of the fast Fourier（anti） transform and the combination of the method of frequency domain and time domain analysis,the transient characteristics of the grounding grid when considering the soil ionization are discussed.The calculation results show that the lower critical breakdown field strength of the soil is,the lower the potential of the injection points is when the lightning impulse strikes grounding grid,and vice versa.The potential difference between the farthest two points of the grounding grid decreases when the soil around the grounding grid is ionized.The grounding grid has the poor capacity to leak the current when the lightning current is injected from the corner point.The degree of the soil ionization is closely related to the soil resistivity.

关 键 词：不等电位 接地网 快速傅立叶(反)变换 雷电冲击 土壤电离 电位差 暂态特性 

分 类 号：TM862[电气工程—高电压与绝缘技术]