20 kV小电阻接地系统高灵敏性接地故障检测方法  

High-sensitive Ground Fault Detection Method for 20 kV Low-resistance Grounding System

作　　者：肖瑞超 李海锋[1] 梁海锋 梁远升[1] XIAO Ruichao;LI Haifeng;LIANG Haifeng;LIANG Yuansheng(School of Electric Power Engineering,South China University of Technology,Guangzhou,Guangdong 510641,China)

机构地区：[1]华南理工大学电力学院,广东广州510641

出　　处：《广东电力》2021年第8期70-79,共10页Guangdong Electric Power

基　　金：广东省基础与应用基础研究基金面上项目(2021A1515010631)。

摘　　要：20 kV电压等级配电网的建设逐渐成为我国大中型城市中压配电网的发展趋势之一。相比于10 kV配电网,20 kV配电网的线路更长,对地电容也更大,这大大增加了对高阻接地故障检测的难度。为此,首先对20 kV配电网的故障特性进行分析;从时域的角度推导线路零序电流及母线零序电压的约束关系,并分析故障线路和正常线路所对应的零序电流和零序电压的时域特征;通过分析得到故障线路和正常线路零序电流与母线零序电压比值绝对值具有明显的差异特征,进而提出一种基于零序电流与母线零序电压微分值比值平均值的高灵敏性接地故障检测方法。最后,基于PSCAD/EMTDC的大量仿真验证所提故障检测方法的有效性,所提方法可将保护耐受过渡电阻的能力提高到1200Ω左右。Construction of 20 kV voltage level distribution network has gradually become one of the development trends of the medium voltage distribution network in the large and medium size cities in our country.Compared with 10 kV distribution network,the lines of 20 kV distribution network are longer and its ground capacitance is larger,which greatly increases the difficulty of detecting the high-resistance ground faults.Therefore,this paper firstly analyzes the fault characteristics of 20 kV distribution network in details,deduces the constraint relationship between the zero-sequence current of the line and the zero-sequence voltage of the bus from the perspective of the time domain,and analyzes the time domain characteristics of zero-sequence current and zero-sequence voltage corresponding to the faulted lines and the regular lines.It is found that the absolute value of the ratio of zero-sequence current of the faulted line and the regular line to zero-sequence voltage of the bus has obvious difference characteristic,and then a high-sensitive ground fault detection method based on the average value of ratio of zero-sequence current and zero-sequence differential voltage of the bus is proposed.Finally,a large number of simulations based on PSCAD/EMTDC verify the effectiveness of the proposed fault detection method.It proves that this method can increase the ability of the protection withstanding the transition resistance to about 1200Ω.

关 键 词：20 kV配电网 故障特性 高灵敏性接地故障 比值平均值 

分 类 号：TM726[电气工程—电力系统及自动化] TM744.3