计及直流偏磁的电流互感器传变特性对差动保护的影响

摘要

由地磁感应电流（GIC）/高压直流输电单极大地回路运行方式引发的直流偏磁会对电磁式电流互感器（TA）的传变特性产生影响,计及直流偏磁影响的TA饱和与无偏磁时相比具有一定的特殊性,会对变压器差动保护产生影响。通过构建考虑直流偏磁的交流系统仿真模型,研究了TA起始饱和时间受直流偏磁的影响及其对变压器差动保护的影响。指出了直流偏磁是TA局部暂态饱和的诱因之一,并通过对直流偏磁条件下和应涌流的仿真研究,分析了TA局部暂态饱和对变压器差动保护的影响。研究结果表明,直流偏磁可能会加速TA饱和,防止区外故障TA饱和引起差动保护误动的时差法判据将受到考验;而直流偏磁诱发的TA局部暂态饱和则可能引起变压器差动保护的误动。%The transferring characteristics of current transformers(TA) are subject to possible changes due to DC magnetic bias caused by geomagnetic induced current(GIC)/high voltage direct current(HVDC).The particularity of TA saturation affected by the DC magnetic bias will severely impact the transformer differential protection system.Based on the AC system simulation models considering DC magnetic bias,the effects caused by the variation of time-to-saturation of protective TAs are studied.Moreover,studies show that DC magnetic bias will lead to TA partial transient saturation.According to simulation of sympathetic inrush with DC magnetic bias,this paper analyzes the impacts on differential protection resulting from the TA partial transient saturation.The research demonstrates that DC magnetic bias may accelerate saturation of protective TAs.This is a challenge to the method of locating the time difference used for preventing maloperation due to TA saturation when external faults occurred.The research also shows that TA partial transient saturation caused by DC magnetic bias may contribute to maloperation of transformer differential protection.