直流电压下界面电荷积聚对“液-固”油纸绝缘电场分布影响的仿真分析及试验验证

Simulation and Verification of Interface Charge Accumulation Influence on Electric Field Distribution of"Liquid-Solid"Oil-paper Insulation Under DC Voltage

界面电荷积聚引起的电场畸变给换流变压器的绝缘性能带来巨大挑战,因此迫切需要针对“液–固”油纸绝缘介质界面电荷对电场分布的影响进行深入研究。首先联合双极性载流子模型、Maxwell-Wagner方程和Poole-Frenkel方程,建立了“液–固”油纸绝缘体系在直流电压下的空间/界面电荷仿真模型,并采用二分迭代法确定了仿真参数。然后在此基础上分别仿真分析了“油隙+油浸纸板+油隙”结构、换流变阀侧出线装置缩比结构的空间/界面电荷分布特性,分析了电荷积聚效应对电场分布的影响,并将考虑了空间/界面电荷影响的电场强度仿真结果与利用克尔效应实际测得的结果进行了对比。结果表明:所提模型及参数适用于直流电压下多层“液–固”油纸绝缘体系的空间/界面电荷分布特性研究;在典型平板多层“液–固”油纸绝缘体系中,电场强度的仿真结果与实测结果基本一致,证明了电荷积聚导致电场发生严重畸变;在换流变出线装置缩比结构中,不同油道的电场强度的仿真结果与实测结果之间的相对误差在3%~7%之间,不仅进一步表明了该仿真方法的有效性,也表明了电荷积聚对电场分布的严重畸变。研究成果为直流电压下考虑电荷积聚效应后多层“液–固”油纸绝缘体系的电场分布计算提供了参考。

The electric field distortion caused by the accumulation of interface charges poses a huge challenge to the insulation performance of converter transformers.Therefore,it is urgent to conduct in-depth research on the influence of the interface charges of the“liquid-solid”oil-paper insulation medium on the electric field distribution.Firstly,by combining the bipolar carrier model,the Maxwell-Wagner equation and the Poole-Frenkel equation,a simulation model of the space/interface charges of“liquid-solid”oil-paper insulation systems under DC voltage was established,and the simulation parameters were determined by the bisection iteration method.Then,on this basis,the space/interface charge distribution characteristics of the“oil gap+oil-impregnated paperboard+oil gap”structure and the reduced-scale structure of the valve-side outlet device of a converter transformer were simulated and analyzed,and the influence of the charge accumulation effect on the electric field distribution was analyzed.Moreover,the simulation results of the electric field intensity with considering the influence of the space/interface charges were compared with the measured results obtained by the Kerr effect.The results show that the established model and parameters are suitable for studying the space/interface charge distribution characteristics of the multi-layer“liquid-solid”oil-paper insulation systems under DC voltage;in the typical flat multi-layer“liquid-solid”oil-paper insulation system,the simulation results of the electric field intensity are consistent with the measured results,which proves that the electric field is seriously distorted by the accumulation of charges;in the reduced-scale structure of the converter transformer outlet device,the relative errors between the simulation results and measured results of the electric field intensity of different oil passages are between 3%and 7%,which not only further shows the effectiveness of the simulation method,but also shows the serious distortion of the electric field distribution caused by the charge accumulation.This paper provides a reference for calculating the electric field distribution of the“liquid-solid”oil-paper insulation systems under DC voltage after the charge accumulation effect is taken into account.