【作者】 杨金飞；

【导师】 张庆超；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2007， 硕士

【摘要】 在小电流接地系统中,当发生单相接地故障时必须迅速发出报警信号并选出故障线路。因此,系统中一般都有选线报警设备。但是目前的选线准确率一直都不是很理想。已有的选线方法几乎都是将零序分量作为比较信号。但是由故障线路流向母线的零序电流不包括故障线路本身的对地电容电流,所以此零序电流缺少故障线路本身的信息量;所有利用零序电流来选线的方法都无法摆脱这一严重缺陷。本文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方法(简称两相法),克服了此缺陷。两相电流旋转变换,即每条线路a, b和c相电流与滞后他们120o的b,c和a相电流经旋转相加,得到两相旋转变换电流(简称两相电流),并将其作为比较量。判据为:非故障线路本身的三个两相电流相等;故障线路本身的三个两相电流之间幅值和相角不同。该方法具有充分的理论推导,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,能准确的辨别故障线路。?60o更多还原

【Abstract】 When a single phase-to-earth fault occurs in non-direct earth neutral system, it is necessary to give an alarming and select the fault line quickly. But, wrong signals are usually made as selecting the fault line in the system.During the past decade many principles and methods have been put forward to solve this problem. Almost all of them are based on comparisons of zero sequence current fundamental wave or harmonic transient component among all the lines. According to the previous experts’studies, zero-sequence current of fault line exclude currents of fault line itself. It is a vital defect to those methods.A novel method of identifying fault line for single phase-to-earth fault in non-direct earth neutral system based on two-phase-current transform (TPCT) is presented. TPCT is one 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 sufficiently from theory. Computer simulation show 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 occurs in non-direct earth neutral system.更多还原