直流偏磁下电流互感器测量特性分析

电流互感器作为电力系统的基本测量单元,其性能对电能计量的准确性有重要影响.随着非线性负荷和绿色能源的大量接入,供电线路电流中出现的直流分量可能严重影响电流互感器的测量准确性,甚至会造成电流互感器铁芯饱和.因此,十分必要对直流偏磁下电流互感器的测量准确性进行评估.文章基于对电流互感器电磁物理特性的分析,建立了存在直流偏磁下表征电流互感器测量特性的解析模型,推导出了电流互感器测量准确性与安匝数、铁芯尺寸、铁芯材料、二次负荷等参数之间的关系式,并对所建模型进行仿真验证得到的结果,对直流偏磁下电流互感器的测量特性进行了讨论.

Magnetic model and measurement characterization of current transformers with DC bias current

As a fundamental measurement unit in power grids, the current transformer plays a significant role in electrical energy metering. As a result of the wide application of nonlinear loads and power recourses in power grids, such as power electronics, green energy generation, etc., undesired DC- current components, in many occasions, present in power lines. A DC bias current can significantly lower the measurement accuracy of a current transformer and, in heavy cases, can saturate the magnetic core of the current transformer. Therefore, it is necessary to evaluate the performance of the current transformer under DC bias currents. Different from the conventional equivalent circuit model of an instrument transformer, we present in this research a magnetic analysis of current transformers under the DC bias condition. An analytical model that links the measurement error to experimental parameters, e.g. ampere-turns, dimensions and material of the magnetic core, load in the secondary winding, etc. The finite element analysis is employed to verify the analytical model. The performance of a typical current transformer with DC and AC is discussed.