变压器差动保护二次谐波制动方案分析与改进

摘要

If the TA is saturated, low second harmonics in transformer differential current will cause false action for differential protection, when the traditional second harmonic restraint strategy is adopted for transformer differential protection in transformer load switching, internal or external fault removal.The harmonic analysis is carried out for the differential current in this paper.Aiming at the problems in traditional second harmonic restraint, a new second har-monic restraint strategy is proposed based on the amplitude and phase of the second harmonic comprehensive criterion. The phase relationship between the fundamental and the second harmonic in inrush current has been researched.The integrated brake criterion is constituted by the second harmonic restraint coefficient adaptively with the second harmon-ics.EMTP simulation results verify the correctness and reliability of the proposed scheme.%变压器差动保护中传统的二次谐波制动方案在变压器空载合闸、内部故障或外部故障切除时，若TA饱和，变压器差流中二次谐波含量较低，差动保护容易误动。文章对变压器差流进行了谐波分析，针对传统二次谐波制动存在的一些问题，提出了基于二次谐波幅值和相位综合判据的二次谐波制动法。研究了励磁涌流中二次谐波与基波之间特殊的相位关系，通过与二次谐波含量构成自适应调整二次谐波制动系数的综合制动判据，并用EMTP进行大量仿真实验，验证了所提出方案正确性和可靠性。