基于两相电流变换的小电流接地系统故障选线新方法

A Novel Method of Fault Line Selection for Non-direct Earth Neutral System Based on Two-phase-current Transformation

提出了两相电流旋转变换小电流接地系统单相接地故障选线新方法(简称两相法)。两相电流旋转变换,即每条线路a,b和c相电流与滞后其120°的b,c和a相电流经-60°旋转相加。新判据为非故障线路本身的3个两相电流相等;故障线路本身的3个两相电流之间幅值和相角不同。计算机仿真表明该算法不受故障电阻和负荷的影响,当系统发生单相接地故障时,能准确辨别故障线路。

A novel method of identifying fault line for single phase-to-earth fault in non-direct earth neutral system based on two-phase-current transformation （TPCT） is presented. TPCT is an algorithm that the currents of phase-a, -b and -c of each line add their leading current of phase -b, -c and -a that is turned 60 degree clockwise, respectively. The criterion of faulted-line identification is that the three-phase currents by TPCT of healthy line are equal while the three-phase currents by TPCT of faulted line are different, which has been proved theoretically. Computer simulation shows that the method of the proposed fault-line identification is not affected by fault resistance and load flow and can identify fault line correctly when a single phase to earth fault occurs in non direct earth neutral system.