表征开口式电流互感器工作原理的解析模型

传统电流互感器一般采用闭磁路铁心设计,但受铁心材料存在磁饱和的限制,其在一次电流回路发生短路故障时,出现的直流电流分量会严重影响电流互感器的性能,导致其测量电流值的误差可能非常大。开口式电流互感器通过在磁路中引入空气隙,大大增加了磁路阻抗,可有效避免铁心饱和对电流互感器性能的影响。从开口式电流互感器的基本磁路和电路时域方程出发,建立了考虑二次侧负载效应时表征开口式电流互感器工作性能的解析模型。讨论了开口式电流互感器的不同参数对其工作性能的影响。所建立的解析模型,对实现测量用电流互感器与保护用电流互感器的兼容,以及提高用于电能表在线检测的钳形电流互感器测量准确度,均具有理论指导价值。

An analytical model of air-gap-core current transformer considering loading effect

The current transformer conventionally employs a closed magnetic circuit design. But limited to the saturation of the magnetic core, when a short-circuit fault occurs in the primary coil, the DC current component will seriously affect the performance of the current transformer, leading to non neglectful errors ??for sensing the primary current. The air-gap-core current transformer increases the magnetic reluctance through the introduction of an air gap in the magnetic circuit, which can effectively reduce the core saturation with DC excitation. Based on fundamental equations of the magnetic and electrical circuits, an analytical model for the air-gap-core current transformer is presented with considering the loading effect of the secondary coil. Influences of different parameters on the air-gap-core current transformer are discussed. The established model supplies basic theoretical guidance towards compatibility of an air-gap-core current transformer for realizing both measurement and protection as well as improving the accuracy of a clamp current transformer that is used for power meter online calibration.