不同故障类型不同转角方式下的变压器差流分析

Analysis and comparison of differential current for different fault type of transformer

详尽分析了变压器差动保护中四种常用转角方式下变压器发生各种内部故障时的差流情况,经理论推导得出了不同故障类型不同转角方式下的变压器差流表达式。着重分析了Y→△与△→Y这两种常用转角方式下两相接地故障时的变压器差流的情况,表明两相接地故障时这两种转角方式的差流与网络结构有关,在差流分析的基础上对这两种转角方式差动保护的灵敏度进行了比较。上述分析是在严格的理论基础上进行,EMTDC仿真实验结果也说明了结论的正确性。

This paper analyzes and compares the differential current of four transformer differential protection schemes with different compensation methods under different fault types and presents the differential current expression by theoretic deduction. It analyzes emphatically the differential current with two compensation methods in common use which are the phase-to-phase current differential protection and phase current minus zero-sequence （self-produced） under two phases ground fault to show that the differential currents is related to the net impedance. Then the sensitivity of the two compensation methods is compared. These conclusion are derived by strict theoretic deduction, and the simulation results based on EMTDC also prove that the conclusion is feasible and effective.