行波小波系数极大值极性法接地故障选线研究

为正确确定故障线路,保证系统安全,提高供电可靠性,研究了配电网中单相接地短路故障时的暂态行波特性。分析变压器的暂态行波特性及其对母线行波电压和线路行波电流的影响表明,行波初始过程中母线电压及各线路电流暂态行波的小波系数的显著规律是故障线路电流暂态行波0模量初始波头的小波系数的极大值极性,总是与其它线路电流和母线电压相反。然后利用暂态行波的小波系数极大值极性特征构成了一种新颖的故障选线保护判据,即利用母线零序电压突变量判断单相接地的时刻,通过识别母线电压及各线路电流初始波头小波系数的极大值极性特征,判断故障线路。利用MATLAB建立了一个典型的配电网系统模型,仿真结果证明该选线算法的有效性,最后对该法的应用提出相关的建议。

Distribution Grid Earth Fault Line Detection Study by Traveling Wave Wavelets Coefficient Maximum Polarities

A single phase earth fault in a distribution grid can usually bring dangerous overvoltage. It is very important to detect the fault feeder for ensuring the safety of power system and reliability of power supply. The paper studies the features of the transient traveling waves of a single phase earth fault taking place in distribution grid, and analyzes the influences of transformer on the features of the transient traveling waves of the busbar voltage and feeders currents. In the primary traveling wave process the winding of a transformer may be approximately equivalent to its input capacity, the influence of the transfoermer winding is feeble and neglectable. So in the primary traveling wave process the rules of the traveling wave wavelets coefficient maximum polarities of the busbar voltage and feeders currents are remarkably distinguished, the zero mode's wavelets coefficient maximum polarity of the fault feeder traveling current traveling wave is in the opposite direction to that of the sound feeders currents and busbar voltage. Using the traveling wave wavelets coefficient maximum polarities of the bus bar voltage and feeders currents' zero modes, a new detection technique based on wavelets is introduced. Identifying the phase failure and the fault time by the zero sequence voltage abrupt changed quantity of busbar, detecting the coefficient maximum polarities of the primary ripples, the fault feeder can be detected. The paper simulates a small typical distribution grid, compiles a simulation failure detecting program. The exactness and availability is proved, and some application advices are brought forward.