电流互感器中性线电阻增大对线路差动保护的影响

发布时间：2018-09-12 13:15

【摘要】：针对电流互感器(TA)中性线电阻增大导致线路差动保护误动的情况,进一步分析了此类误动产生的原理和机理。TA中性线电阻大于一定数值时,故障相二次回路电流在中性线上产生的电压降会使非故障相TA在二次侧出现类似励磁涌流的效应,从而产生波形偏向一侧的异常电流,其本质原因是TA磁链的累积。此外,通过改变二次回路方程的参数研究了中性线电阻大小、非周期分量大小、剩磁水平,以及TA容量对异常电流幅值的影响。在研究、归纳了此类误动的各种特征后,提出将三相最大电流引入制动判据中,结合该相二次谐波基波比,识别TA中性线异常后短时闭锁分相差动保护的动作逻辑。经仿真与录波图回放验证了所提保护方案的正确性和有效性。
[Abstract]:In view of the maloperation of line differential protection caused by the increase of (TA) neutral line resistance of current transformer, the principle and mechanism of this kind of misoperation are further analyzed when the neutral line resistance of TA is greater than a certain value. The voltage drop of the secondary circuit current in the fault phase on the neutral line will make the non-fault phase TA appear the effect of excitation inrush current on the secondary side, resulting in the abnormal current of the waveform tilting to one side, which is essentially due to the accumulation of the TA flux. In addition, by changing the parameters of the quadratic loop equation, the effects of the resistance of neutral line, the size of aperiodic component, the level of remanence and the capacity of TA on the amplitude of abnormal current are studied. After studying and summarizing the characteristics of this kind of maloperation, the paper puts forward that the three-phase maximum current is introduced into the braking criterion, combined with the second harmonic fundamental wave ratio of the phase, to identify the action logic of short-time lock-phase differential protection after the anomaly of TA neutral line. The correctness and effectiveness of the proposed protection scheme are verified by simulation and playback.
【作者单位】：华北电力大学电气与电子工程学院;北京四方继保自动化股份有限公司;
【分类号】：TM452;TM773

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