基于轴对称模型的特高压变压器直流偏磁分析

文中针对特高压自耦变压器三维模型直流偏磁计算耗时长的问题,通过分析特高压变压器的磁路结构特点,建立了特高压变压器的等效轴对称二维模型,有效减小直流偏磁计算规模。与三维模型进行对比,验证了轴对称模型的正确性和有效性。轴对称模型能够在较短的时间内完成偏磁计算,有效减少直流偏磁的计算工作量,且计算精度可以保证,相较于三维模型有一定优势。在轴对称仿真模型的基础上,进一步分析串联电阻及时间步长对直流偏磁计算精度的影响,并获得了串联电阻的取值范围。最后,通过时域场路耦合原理进行不同直流电流下的特高压变压器负载直流偏磁求解,分析直流偏磁的电磁效应。结果表明,随着直流偏磁电流的增加,励磁电流及绕组电流波形发生严重畸变,并产生很大的谐波分量,影响变压器乃至电力系统的安全稳定运行。

DC Magnetic Bias Analysis of UHV Transformer Based on Axisymmetric Model

Aiming at the time-consuming problem of the DC magnetic bias calculation for three-dimensional model of UHV autotransformer,an equivalent axisymmetric two-dimensional model is established by analyzing the features of magnetic circuit structure of UHV Transformer so as to effectively reduce the computation scale of DC magnetic bias.The correctness and effectiveness of the axisymmetric model are verified by comparing with the three-dimensional model.The axisymmetric model can complete the calculation of DC magnetic bias in a relatively short time,effectively reduce the computation workload,and guarantee the accuracy of calculation.And it has a certain advantage over the three-dimensional model.Based on the axisymmetric simulation model,the influences of series resistance and time step on the calculation accuracy of DC magnetic bias are analyzed,and the range of the series resistance is obtained.Finally,the DC magnetic bias of UHV transformer under different DC current is calculated according to the magnetic-circuit coupling principle in time domain,and the electromagnetic effect of DC magnetic bias is analyzed.The results show that with the increase of DC magnetic bias current,the waveforms of excitation current and winding current distort seriously,and large harmonic components are produced,which will threaten the safe and stable operation of transformers and even the power system.