基于Lax-Wendroff算法的变压器绕组高频模型的时域分析

特快速暂态过电压(VFTO)作用下变压器绕组的过电压分布计算对于其绝缘设计是非常重要的。为研究VFTO对大型电力变压器绕组绝缘的影响,笔者首先不考虑频变阻抗的影响,针对容易损坏的前几匝线圈,每匝线圈为一单元构造模型,其余线圈以两饼线匝为一单元,建立变压器绕组的多导体传输线模型,利用三阶精度的Lax-Wendroff差分法计算暂态电压分布;然后采用矢量匹配法处理频变参数,推导基于Lax-Wendroff差分法的暂态计算公式。计算结果与电磁暂态程序EMTP仿真结果一致,验证了该方法的可行性和有效性。

Time-domain Analysis of High-frequency Model of Transformer Windings Based on Lax-Wendroff Algorithm

Calculation of over-voltage distribution of transformer windings under very fast transient over-voltages(VFTOs)is very important to insulation design of electric transformers.In order to investigate over-voltage distributions of large-scale electrical transformer windings under VFTOs,a model using centralized parameters is presented in this paper.For the first several easily-burnt windings,neglecting frequency-varied impedance effect,each winding is modeled as one unit,and other windings are modeled every two windings as one unit,then a multi-conductor transmission line model(MTLM)for transformer windings is proposed.Transient over-voltage distributions are computed via the Lax-Wendroff difference method with third-order precision,and the frequency-varied parameters are dealt with by the vector fitting method to deduce transient computational formulas based on the Lax-Wendroff difference method.Computational results are consistent with the simulation ones of the electromagnetic transient program(EMTP),which verifies the feasibility and validity of the proposed algorithm.