【摘要】 与电力变压器相比，电磁式电压互感器（PT）具有更大的杂散电容，这将使其磁滞曲线的绘制以及宽频仿真模型的构建更加困难，难以进行精确的铁磁谐振仿真。目前，工程上常用频率扫描的方式计算高频高压变压器的分布电容。但是该方法需要数MHz的扫频范围，难以应用于工作在低频下的PT设备。该文提出一种低频窄带的频率扫描方法，通过在PT与变频电源端口之间串联电感的方式，将扫频试验的谐振点降至低频范围内，对杂散电容的数值进行了精确计算。该方法所需的扫描频段窄、扫描频率低，降低了对电源与测量设备的硬件要求，避免了由于高频试验带来的损耗问题。进而，可以分离PT端口电流中的容性电流与励磁电流分量，对磁滞曲线进行精确绘制。最终，可以建立包含铁心磁滞与杂散电容的π型仿真模型。仿真结果具有较好的频率响应特性，与试验结果的相似系数保持在95%以上，优于现有的仿真模型。更多还原

【Abstract】 The low-frequency responses of potential transformers(PT) are essential in power system protection. Due to the complex winding structure and large transformation ratio, the stray capacitance will significantly impact the dynamic performance of the PT. Many studies have analyzed the distribution of the electric field and magnetic field energy of the PT at low frequencies to determine its modeling method of it.However, it is difficult to obtain the stray capacitance value of a PT without its detailed internal structure parameters, which makes it challenging to build an accurate low-frequency simulation model.Firstly, the electric field energy distribution for two typical winding structures was analyzed, and the corresponding stray capacitance values could be calculated. The capacitance calculation method explained the generation mechanism of the PT and could provide references for the design progress. However, most users of the PT are not involved in the design progress and need help understanding its detailed internal structure parameters.Therefore, a non-destructive experiment method is necessary for the stray capacitance evaluation. Secondly, the equivalent model of PT stray capacitance distribution at low frequency was built, and the low-frequency dynamic responses under electromagnetic field coupling of the core and coil were analyzed. The obtained model can provide support for the experimental designs. Finally, a series of tests were carried out to obtain the specific value of PT stray capacitance. By connecting the inductance in series between the PT and the frequency conversion power supply port, the resonance point of the sweep frequency test was reduced to the low-frequency range, and the value of the stray capacitance was accurately calculated. Since this method requires a narrow scanning frequency band and a low scanning frequency, the hardware requirements for power supply and measuring equipment are reduced, and the loss problem caused by high-frequency testing is avoided. Furthermore,the capacitive and excitation current components in the PT port current could be separated, and the hysteresis curve could be accurately drawn.Based on the problem that it is difficult to measure the PT stray capacitance and hysteresis curve in engineering, this paper reduced the resonant frequency point of the sweep frequency test using series inductance and calculated the stray capacitance. Furthermore, the capacitive component in the current of the PT port could be excluded, and the accurate drawing of the hysteresis curve of the iron core could be realized. Combined with the short-circuit test and DC resistance measurement results, the π-type equivalent circuit of PT was constructed.The simulation results had good frequency response characteristics. The Pearson correlation coefficient was introduced to study the accuracy of the simulation model, and the correlation coefficient with the test results remained above 95 %. Due to the accurate description of the inductive and capacitive coupling, the model can be applied to the ferromagnetic resonance simulation of a power system to obtain more accurate simulation results and provide a reference for the design of the anti-resonance scheme.更多还原