Frequency response analysis is widely used as a method for the offline diagnosis of winding deformations in power transformers. To apply it to a working transformer, people need to determine how to inject the excitation signal and measure the response signal for windings that bear a rated voltage and current. In this study, a method to obtain the frequency response curve online is proposed. It uses the principle of magnetic field coupling to inject a frequency sweep signal into the windings through a Rogowski coil. Another Rogowski coil sensor placed at the root of a high-voltage bushing is used to measure the response current signal. Experiments on a 72.5 kV bushing show that metal accessories of the bushing have no influence on the injection or the measurement. The feasibility of this method was verified by experiments on charged 110/35/10 kV transformers at a factory and a working 35 kV transformer in a power station. The results show that it is safe to install the Rogowski coil at the root of the high-voltage bushing. The excitation signal can be injected into live windings and the response signal is measurable. Strong electromagnetic power frequency noise can be reduced and the frequency response curve can be measured online.

中文翻译：

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基于磁耦合的在线频率响应分析以检测变压器绕组变形

频率响应分析被广泛用作离线诊断电力变压器绕组变形的方法。为了将其应用于正常工作的变压器，人们需要确定如何注入励磁信号并测量带有额定电压和电流的绕组的响应信号。在这项研究中，提出了一种在线获取频率响应曲线的方法。它使用磁场耦合原理，通过Rogowski线圈将扫频信号注入绕组。放置在高压套管根部的另一个Rogowski线圈传感器用于测量响应电流信号。在72.5 kV套管上进行的实验表明，套管的金属附件对注入或测量没有影响。通过对工厂中的带电110/35/10 kV变压器和电站中工作的35 kV变压器进行实验，验证了该方法的可行性。结果表明，将Rogowski线圈安装在高压套管的根部是安全的。可以将激励信号注入带电绕组中，并且可以测量响应信号。可以减少强电磁功率频率噪声，并且可以在线测量频率响应曲线。