基于EMTDC的三相变压器励磁涌流分析

Analysis for Inrush Current of Three-Phase Transformer Based on EMTDC

针对当前变压器差动保护不同程度的误动现象 ,利用EMTDC建立电源 变压器 电流互感器的系统模型 ,综合仿真变压器不同角度空载、满载合闸时的励磁涌流及经电流互感器传变后的二次涌流 ,获得不同合闸角时的二次谐波含量和涌流间断角的大小。仿真结果表明 ,一次涌流经电流互感器传变后 ,涌流特征并未变化 ,故不会使保护误动 ,同时 ,无论变压器有、无剩磁 ,任一合闸角都不会使差动保护误动 ,用仿真分析结果可重新校定差动保护动作闭锁条件。

To solve the problem of misoperation in differential protection of transformer, a system model composed of power source, transformer and current transformer is established and a few simulations are carried out by applying EMTDC software. Inrush currents are simulated when transformer is switched on with different angle under no load and full load; the second inrush current flowing through current transformer is also simulated. The second harmonic content and dead angle of inrush current under different switch-on angle are obtained from the simulations. It indicates from the simulations that the characteristic of inrush current remains unchanged after flowing through the current transformer, and thus it could not make misoperation. At the same time, it can not make the differential protection to act under any switch-on angle, whether transformer has surplus magnetism or not. The blocking condition of differential protection could be re-corrected by using simulation results.