知识与财富的链接
针对纵联零序方向零压不够时保护拒动的实际问题,考虑到系统中各站点间的负序转移阻抗远小于零序转移阻抗,单相接地故障时负序电压大于零序电压这一特点,论文提出了基于负序分量补偿的方向保护补充判据。判据进行了周密的实用化考虑,利用故障后零负序电压与电流的相位关系来判别故障方向,在深入分析判据动作特性及灵敏度的基础上,按照故障特征的差异逐步提高灵敏度,综合构成了较完善的纵联接地方向保护方案。实例验证与仿真结果均表明,由该负序分量补偿的纵联零序方向保护在零序方向元件因电压不足而拒动时,能可靠判别故障方向,并具有良好的可靠性与选择性,从而有效改善了纵联接地保护的性能。
If the zero sequence voltage is not sensitive enough,the pilot zero sequence directional protection will not operate correctly.Considering the negative sequence transfer impedance between stations is much smaller than zero sequence transfer impedance between stations,and the negative sequence voltage is greater than the zero sequence voltage when single phase fault occurs,a new criteria based on the composition of negative sequence component is proposed.The detailed actual applications are considered in the criteria.According to the phase relationship between zero and negative sequence voltage and current after fault,the fault direction can be calculated.After analyzing the characteristic and sensitivity of criteria deeply,the sensitivity can be improved step by step,and then a complete pilot directional earth fault protection scheme is finished.The result of actual system and simulation demonstrate that the criteria can judge the fault direction reliably with good reliability and sensitivity.So the new criteria can effectively improve the performance of pilot directional earth fault protection.
