含水率对复合电场下油纸绝缘电场分布的影响

Moisture influence on the electric field distribution of oil-pressboard insulation under compound electric field

为研究含水率对换流变压器油纸绝缘电场分布的影响,以典型油纸绝缘结构为研究对象,首先根据典型油纸绝缘结构建立了其等效物理模型和电路模型,并得到了复合电场下电场分布的数学表达式。结合不同温度及含水率下变压器油和浸油纸板绝缘电阻率及相对介电常数的测量结果,通过仿真分析得出了复合电压作用下油纸绝缘中电场分布与含水率及交流含量的关系。研究结果表明,水分对复合电压作用下油纸绝缘的电场分布有着显著的影响,当水分达到平衡状态时随含水率的增加油中场强增强、浸油纸板中场强减弱;随着绝缘体系整体含水率的上升,油纸绝缘电场分布的变化呈加速趋势;水分对油纸绝缘电阻率的影响远高于其对相对介电常数的影响,从而导致水分对高直流分量复合电压下的油纸绝缘电场分布产生较大影响。

In order to study the moisture influence on the electric field distribution of oil-pressboard insulation in converter transformer, the equivalent physical model and circuit model were established according to the typical oil-pressboard crmpound insulation structure, and the mathematical expression for electric field distribution calculation under compound electric field was obtained. According to the measured re- sults of resistivity and relative permittivity of transformer oil and oil impregnated pressboard with different moisture under different temperature, the relationship between electric field distribution and moisture ＆ AC content was obtained for typical oil-pressboard insulation under compound voltage. The results show that the moisture has great influence on the electric field distribution of oil-pressboard insulation under compound voltage. With moisture increasing, the electric field strength in oil will be enhanced; mean- while electric field strength in oil-impregnated pressboard will be reduced, when moisture in oil and pressboard reaches equilibrium state. When the oil-pressboard insulation moisture increases, the electric field strength varies accelerated. The moisture has more influence on oil-pressboard resistivity than that on permittivity, which results in the great moisture influence on the electric field distribution in oil-press- board insulation under compound voltage with the higher DC content.