电磁式电压互感器“低频过电压激励-响应”逆问题求解

Solution of the Inverse Problem of“Low-Frequency Overvoltage Excitation to Response”for Electromagnetic Potential Transformers

电磁式电压互感器(PT)作为电力系统中已大规模应用的电压感知设备,在低频电磁暂态电压激励下可能出现铁心饱和,引起二次响应电压波形畸变、测量误差激增。通过求解PT的“低频过电压激励-响应”逆问题,由PT二次响应电压计算得到其一次激励电压。该文基于电磁对偶原理建立计及铁心深度饱和特性的PT正向电路模型及其参数提取方法,进而构建其逆向数学模型,提出PT“低频过电压激励-响应”逆问题的求解方法。针对10kV真型PT的低频暂态仿真与试验数据进行“低频过电压激励-响应”逆问题求解方法的验证,结果表明:提出的逆向求解方法可将PT的低频电磁暂态测量误差从65.6%降低至10%,解决了其在低频暂态电压激励下的测量失真难题。

Electromagnetic potential transformer(PT)is a piece of critical voltage measurement equipment widely used in power systems.However,low-frequency electromagnetic transient voltages may excite the core of PT to be saturated,resulting in a significant increase in measurement error.By solving the inverse problem of“low-frequency overvoltage excitation to response”of PT,its primary excitation voltage can be calculated based on the secondary response voltage.Based on the principle of electromagnetic duality,a forward circuit model considering the deep saturation of the iron core and its parameters extraction method are proposed in this paper,then an inverse mathematical model is constructed,which solves the inverse problem of“low-frequency overvoltage excitation to response”of PT.The proposed method is validated by simulations and experiments on a 10kV PT.Results show that the proposed method can significantly decrease the error of the PT from 65.6% to 10%,when it suffers from deep saturation caused by low-frequency transients.The proposed method solves the problem of distortion of the secondary voltage of the PT under the excitation of low-frequency transients.