采用瞬态上流元法的油纸绝缘瞬态电场研究

Study of transient electric field of oil-paper insulation with transient upstream finite element method

作为换流变压器的主要绝缘材料,油纸复合材料的绝缘特性受内部空间电荷的影响.在极性反转电压下,介质内部积聚电荷产生附加场强,可能使局部电场明显增强,从而更易引起绝缘击穿.基于瞬态上流有限元数值方法,引入界面势垒模型,计算极性反转条件下单层油浸纸、油浸纸-油双层绝缘结构内部空间电荷的运动特性以及瞬态电场随时间的变化规律,并与试验得到的规律进行对比验证.仿真结果表明:在直流电压下,介质内部积聚的电荷无法快速消散,将对反转瞬间的电场产生叠加作用,引起电极附近场强最大程度畸变.双层介质的界面阻碍效应产生的界面积聚电荷,导致在极性反转瞬间油中电场瞬时增大.研究结果可为换流变压器油纸绝缘特性和击穿场强研究提供参考.

The insulation property of oil-paper composite material,as main insulation material of converter transformer,is influenced by internal space charges.Under polarity reversal voltage,the accumulative charges inside the insulation will produce additional field strength and significantly enhance the local electric field,which tends to cause insulation breakdown.The interfacial barrier model was adopted based on the transient upstream finite element method(TUFEM),and the charge motion characteristics and transient electric field under polarity reversal in singlelayer oil-impregnated paper and two layers of oil-impregnated paper and oil were calculated.The simulation results were compared with the experiment results to verify applicability of the numerical method.Results showed that internal accumulative charges formed under direct current voltage were unable to dissipate quickly,which had a superposition effect on electric field at the instant of polarity reversal,causing the maximal electric field distortion near the electrodes.The accumulative charges at the interface due to interfacial blocking effect will lead to sudden increase in electric field of oil.The conclusion can provide reference for the study of oil-paper insulation characteristic and breakdown strength.