用于过电压检测的电流互感器高频等效电路建模方法

Modeling Method of High-frequency Equivalent Circuit of Current Transformer for Overvoltage Detection

电力系统中设备的绝缘性能非常重要,而过电压是引发设备绝缘损坏的主要威胁之一,采用电流互感器可以有效监测电力系统中的过电压。文中针对基于末屏电流检测的过电压传感器提出了一种电流互感器的高频等效电路建模方法,解决目前低频建模方法无法准确模拟过电压中高频(MHz)分量的问题。该方法可以在不改变电力设备一次接线方式的前提下,实现包括工频过电压、操作过电压以及雷电过电压在内的各种过电压传感器的准确建模。分析了高频时电流互感器的电磁谐振特性,并据此建立了包含多个谐振频率的RLC高频等效电路。通过仿真算例和实验测试,验证了所提模型的准确性。通过所提等效电路即可根据电流互感器的末屏电流来计算过电压的大小,从而有效评估绝缘风险、保障电网安全运行。

The insulation performance of equipment in the power system is very important,and overvoltage is one of the main threats that cause insulation damage of the equipment.The use of current transformers can effectively monitor the overvoltage in the power system.In this paper,a kind of high-frequency equivalent circuit modeling method of current transformers for overvoltage sensors based on last-screen current detection is proposed to solve the problem that low-frequency current modeling methods has no way to accurately simulate the intermediate and high-frequency(MHz)components of overvoltage.The method can,on the premise not changing the primary wiring mode of power equipment,achieve accurate modeling of various overvoltage sensors including power frequency overvoltage,operating overvoltage and lightning overvoltage.Firstly,the electromagnetic resonance characteristics of the current transformer at high frequency are analyzed and,on this basis,the RLC high-frequency equivalent circuit containing multiple resonance frequencies is set up.Then,through simulation examples and experimental tests,the accuracy of the proposed model is verified.The proposed equivalent circuit can be used to calculate the magnitude of the overvoltage according to the last screen current of the current transformer,thus effectively assessing the insulation risk and assuring safe operation of the power grid.