基于混合电场线性叠加原理的换流变压器内部电场分布规律研究

换流变压器是特高压直流输电系统中的关键设备，其阀侧承受着交直流复合电压。研究热老化对交直流电压在油纸绝缘内分布的影响，可为换流变压器油纸选型提供理论借鉴。选取了换流变压器常用的绝缘油和绝缘纸作为研究对象，并对2种不同油纸组合展开加速热老化试验，测量并分析试验过程中绝缘油和绝缘纸的介电常数和电阻率的变化规律，在此基础上通过油-绝缘纸-油有限元电场仿真模型分析，基于线性叠加原则，得到了交直流电压在热老化过程中的分布变化情况，表明热老化主要影响油纸中直流分量的分布，将显著提高油中的电场强度。

Effect of Thermal Aging on Electric Field Distribution in Converter Transformer Based on Linear Additive Principle for Mixed Electric Field

Converter transformer is the key electrical equipment of UHVDC transmission system， and its valve side is subjected to compound AC and DC voltage. Studying the effect of thermal aging on the distribution of AC and DC voltage in oil-paper insulation provides a theoretical reference for the selection of the oil-paper in the converter transformer. The paper carries out research on insulating oil and paper commonly used in the converter transformer， and conducts the accelerated thermal aging test on two different oil-paper combinations. The change in the dielectric constant and resistivity of the insulating oil and paper during the test is measured and analyzed. Based on the oil-insulating paper-oil finite element electric field simulation model analysis， the distribution variation of AC and DC voltage during the thermal aging is obtained according to the linear additive principle of mixed electric field， indicating that the thermal aging mainly affects the distribution of DC component in the oil-paper and significantly increasing the electric field in oil.