CAJ | 학술논문

在高压直流(high-voltage direct current,HVDC)输电系统中,换流变压器受各种交直流滤波器影响,发生不对称故障时,差动电流中2次谐波含量比较大.通过仿真分析可知,采用2次谐波制动时,某些故障情况下保护会发生拒动.经分析,励磁涌流波形具有间断和偏向时间轴一侧的特征,而故障时的差动电流在不计直流分量影响的情况下,其波形分布时间轴两侧且无间断角.据此,提出利用变压器二次出口采样电流与标准正弦曲线之间的欧氏距离来鉴别励磁涌流和故障电流.通过EMTDC进行了大量的仿真实验,验证了该判据的稳定性和有效性.
재고압직류(high-voltage direct current,HVDC)수전계통중,환류변압기수각충교직류려파기영향,발생불대칭고장시,차동전류중2차해파함량비교대.통과방진분석가지,채용2차해파제동시,모사고장정황하보호회발생거동.경분석,려자용류파형구유간단화편향시간축일측적특정,이고장시적차동전류재불계직류분량영향적정황하,기파형분포시간축량측차무간단각.거차,제출이용변압기이차출구채양전류여표준정현곡선지간적구씨거리래감별려자용류화고장전류.통과EMTDC진행료대량적방진실험,험증료해판거적은정성화유효성.
Due to impacts of the filters in AC and DC fields in HVDC systems, the differential current contains large amount of 2nd order harmonic, the differential protection of the converter transformer may fail to trip in case of asymmetric internal faults. The simulation results prove that the 2nd order harmonic restraint criterion is not sufficient when applied to differential protection for converter transformer. As the magnetizing inrush contains dead angle and bias in one side of the time axis while the fault current is nearly sinusoid, a new method by measuring the Euclidean distance of sampling current of transformer and sine curve is proposed to discriminate the magnetizing inrush and the fault current of converter transformer. Stability and validity of the proposed criterion are verified with numerous simulation tests based on EMTDC.