油纸绝缘内部合成电场数值模拟方法

油纸绝缘作为换流变压器的主绝缘介质,其内部电场的分布受外加电压以及空间电荷的影响,而传统的数值方法无法准确计算空间电荷的影响。提出一种基于电极肖特基发射理论和瞬态上流元法(TUFEM)求解载流子输运方程的方法,计算了考虑注入势垒、载流子迁移率、陷阱捕获系数以及载流子复合系数等参数影响下的单层油纸绝缘介质内部空间电荷运动分布特性。与试验结果对比表明瞬态上流元法的有效性。研究典型油纸绝缘介质结构内部合成电场强度畸变程度随温度梯度变化的特性。同时,计算得到极性反转电压下不同时刻的电荷运动和电场分布规律。该方法可推广在(特)高压直流换流变压器内绝缘电场计算和优化设计。

Numerical Simulation Method of Electric Field in Oil-Paper Insulation

The oil-paper insulation as the main insulating medium of the converter transformer, its distribution of electric field is influenced by applied voltage and space charge. The traditional numerical methods fail to figure up the influence of space charge accurately. In this paper, a method based on Schottky emission theory and transient upstream finite element method (TUFEM) was proposed to solve the carrier transport equations. The simulation of charge motion characteristics in single oil-paper insulation was carried out considering electrode implantation barrier, carrier mobility, trap coefficient and carrier recombination coefficient. Compared with the test results, the simulation results indicate this method has high accuracy. The effects of temperature gradient on the electric field intensity distortion in oil-paper insulation were studied. Moreover, the charge movement and electric distribution at different time moments under the polarity reversal voltage were calculated. This method can be applied to the calculation and optimization design of the insulation electric field in the high voltage DC converter transformer.