直流偏磁对电流互感器的性能影响研究

发布时间：2018-04-11 04:17

本文选题：电流互感器 + 直流偏磁　；参考：《重庆大学》2014年硕士论文

【摘要】：目前我国大量的东西输电线路的建设、长距离输电系统的发展建设以及全国联网战略的逐步实施使电力系统很容易受到地磁感应电流的影响，这使得交流电网中的直流分量问题更加突出。电磁式电流互感器作为电力系统中重要的设备之一，直流偏磁现象对电流互感器的影响不容忽视，研究分析直流偏磁对电流互感器的性能的影响具有重大的理论和工程意义。本论文通过电流互感器的T型等效模型分析了其工作原理，并推导出了电流互感器的误差与铁芯磁导率之间的关系，利用铁芯电感与磁导率之间的正比关系设计了铁芯性能实验，得到了在直流偏磁下电感与铁芯磁导率之间的变化规律。设计了交直流混合的电流互感器误差实验方法，该方法适用于现场封装完整的只留出一次侧和二次侧端子的电流互感器。通过直流偏磁误差实验得出，随着直流偏磁分量的增加，电流互感器的铁芯有效磁导率将减小，从而导致其误差增大，比差曲线整体往负方向偏移，相差曲线整体往正方向偏移。通过直流偏磁误差实验，同时得到了随着直流偏磁分量的增加，电流互感器二次侧的低次谐波明显增加，当直流偏置百分比在大于3%后，偶次谐波将大于奇次谐波，二次波形将发生严重畸变。通过剩磁实验得出了直流偏磁对电流互感器误差的影响与剩磁类似。利用电流互感器铁芯的基本励磁曲线模拟饱和运行时的磁滞回线，并利用MATLAB建立电流互感器仿真模型，分析在直流偏磁下电流互感器的饱和特性。通过理论和仿真分析，得到正向直流偏磁会将电流互感器的起始饱和时刻提前，反向直流偏磁会将电流互感器的起始饱和时刻推后。从原理上分析了采样值差动保护制动性能不差于传统相量差动保护时判据判别次数的取值范围，并分析了在直流偏磁对制动判据的影响。分析了在不同差动电流初始采样角的情况下采样值差动保护动作判据的模糊区。通过MATLAB建立区内故障和区外故障的模型，在躲开动作判据模糊区的情况下确定采样值差动保护的动作判据并进行仿真分析。针对各种情况对采样值差动保护进行仿真分析，，并提出了差动保护方案。
[Abstract]:At present our country a lot of transmission line construction, development and construction of long distance transmission system and the gradual implementation of the strategy of the national network of electric power system is vulnerable to the effects of geomagnetically induced current, which makes the DC components in AC power network is more prominent. The electromagnetic current transformer as one of the most important equipment in power system, influence the phenomenon of DC bias current of the transformer can not be ignored, it is of great theoretical and engineering significance to study the influence of DC bias on the performance analysis of current transformer.
This paper analyzes the working principle of the T type equivalent model of the current transformer, and deduces the relationship between error and core permeability of current transformer, the core performance test is designed by using the proportional relation between the iron core inductor and the magnetic permeability, the change regularity between inductance and core permeability under DC bias. Design of hybrid AC / DC current transformer error test method, this method is applicable to only one side of the site set aside the complete package and two side terminals of the current transformer DC bias error. Through experiments, with the increase of the DC bias component, the core permeability of current transformer will be reduced, resulting in the error increases, difference curve shifts to negative direction, the overall difference curve shifts to positive direction. The DC bias error in the experiment, and obtained with DC bias component Increase, low harmonic current transformer secondary side two increased significantly, when the DC bias in percentage is greater than 3%, even harmonics will be greater than the odd harmonics, the two wave will have a serious distortion. Through the remanence experiments of DC magnetic bias effect on the error of current transformer with similar remanence.
Simulation of hysteresis loop saturation at runtime using the basic excitation curve of current transformer core, and use MATLAB to establish simulation model of current transformer under DC bias, analysis of current transformer saturation characteristics. Through theoretical analysis and simulation, positive DC bias will start current transformer saturation time, reverse DC magnetic bias will start current transformer saturation time later.
From the principle of sampling value differential protection braking performance difference range from the traditional phasor differential protection criterion number, and analyzed the influence of braking criterion in the DC bias. The analysis of sampling value differential protection criterion of fuzzy region at different initial sampling angle of differential current situation. The establishment of the internal fault and external fault model by MATLAB, in the escape action criterion of fuzzy region under the condition of determining the differential protection criterion and simulated sampling value. According to the situation of the differential protection simulation analysis and put forward the sampling value differential protection scheme.

【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM452

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