【作者】 桑丙玉；

【导师】 王晓茹；

【作者基本信息】 西南交通大学 ， 电力系统及其自动化， 2009， 硕士

【摘要】 特高压输电具有输电成本经济、电网结构简单、输电走廊占用少等优点。根据我国能源结构特点和电力系统规模的扩大,我国已决定建设特高压输电系统,晋东南—南阳—荆门1000千伏特高压交流输电工程已于2009年1月投入运营。基于基尔赫夫电流定律的电流差动保护是特高压输电线路主保护之一。特高压输电线路对继电保护性能要求更高,其特殊结构和特点对线路的电流差动保护又有很大的影响:较大的线路分布电容电流、严重的暂态过程、较大的过渡电阻及可能加入的串并联补偿,都会对线路电流差动保护产生影响。本文分析综述了国内外特高压输电的发展及超特高压输电线路电流差动保护的研究现状,指出了特高压输电线路电流差动保护存在的关键问题;分析了几种典型的输电线路电流差动保护原理和动作判据;基于电力系统电磁暂态仿真软件PSCAD/EMTDC,建立了典型的1000kV、750kV和500kV输电线分布参数模型,仿真比较了线路的分布电容电流及其对电流差动保护的影响;分析了稳态电容电流补偿方法存在的不足,提出了一种改进的自适应电容电流补偿方法,并在1000kV线路模型上进行了仿真验证;基于输电线的微分方程,推导了输电线路空载合闸和线路故障的暂态电流表达式并进行了仿真验证,给出了带串并联补偿的线路方程和暂态电流推导方法;分析了特高压输电线路暂态电流的特征及其对电流差动保护的影响,研究了几种典型的电流差动保护在空载合闸、区外故障、区内不同点故障及不同过渡电阻故障情况下的性能,在此基础上提出了一种适合于特高压输电线路的电流差动保护改进判据,并在1000kV线路上对此判据在空载合闸、区外故障、区内不同故障条件下的动作特性进行了仿真分析,证明了改进判据的正确性和有效性。更多还原

【Abstract】 Ultra-High-Voltage has a economic transmission cost,a simple grid structure,less power transmission corridors,etc.According to the characteristics of China’s energy structure and the expanded scale of the power system,China has decided to build UHV transmission system,the Jindongnan-Nanyang-Jingmen 1000kV UHV AC Transmission Project was put into operation in January 2009.The current differential protection based on KCL current theory is one of the main protection of UHV transmission lines.UHV transmission lines has higher performance requirements of relay protection,and its special structure and characteristics have a great impact to the current differential protection.The larger distributed capacitance current,the seriously transient process, the larger fault resistance and the probable accession of series capacitor or paraller reactor will all have an impact on line current differential protection.This development of UHV transmission about domestic and international is summarized,the present research situation of EHV/UHV line current differential protection is analysed and the key issues of UHV line current differential protection is pointed out.Several typical line current differential protection principles and action criteria is analysed.Based on the power system electromagnetic transient simulation software PSCAD/EMTDC,typical 1000kV,750kV and 500kV transimission line model is simulated.The distributed capacitance current of the models is compared and its impact on the current differential protection is analysed.With analysis of the shortage of steady-state capacitance current compensation,an improved self-adaptive capacitance current compensation method and its simulation in 1000kV line model is carried out. Based on the differential eguation of transmission line,the transient current expression of no-load closing and line fault is deduced and validated.The characteristics of transient current and its effect on current differential protection is analysed.The performance of several typical current differential protection in no-load closing,external fault,internal different fault point and resistance is studied.Based on the result,a suitable UHV transmission line improved current differential protection criterion is brought forward.Based on the 1000kV line model,the action characteristics of the improved protection criterion in no-load closing,external fault,internal different fault conditions is simulated and analysed,the results proved the correctness and effectiveness of the improved criterion.更多还原