工频双极性方波电场下环氧树脂的空间电荷特性

Space Charge Characteristics of Epoxy Resin Under Power Frequency Square Wave Field

为研究环氧树脂在双极性方波电场的空间电荷积累现象,以上升沿200μs和频率50Hz的双极性方波为极化电场,检测0.83~16.63kV/mm范围下环氧内部的空间电荷动态响应,并结合红外光谱的交联副产物分析,探讨电场幅值对空间电荷积累量及最大电场畸变率的影响。结果表明:环氧树脂表面层的空间电荷为异极性电荷占主导,48h真空脱气后其电荷量明显下降,与交联副产物等杂质相关的官能团量明显下降趋势一致。这表明交联副产物是空间电荷的主要来源之一,解离形成的正、负离子在电场作用力驱动下向极性相反电极定向迁移后,在试样表面层形成明显的异极性电荷积累。全周期平均相位体电荷密度中的绝对值密度ρa、正电荷密度ρ+和负电荷密度ρ-随外施场E均呈现指数n≈1增长,与欧姆传导的特征指数n=1相近。这表明检测电场范围可能在欧姆传导区,载流子源中杂质离子电荷占主导。负半周期ρa、ρ+和ρ-均呈现出指数n≈1的欧姆传导输运特征,而正半周ρa、ρs和ρ-均呈现出n在1.130~1.159的指数增长;全周期ρs、正半周期ρ+和负半周期ρ-呈现出了明显的三段试增长,存在2个明显的阈值电场,且最大电场畸变率δmax整体约在9%~17%左右。这可能主要与下电极侧试样在正、负半周期电场下的杂质离子电荷和电极注入电荷的量以及分布区域动态平衡相关。

In this paper,the space charge accumulation of epoxy resin is analyzed based on the space charge detection under a bipolar square wave electric field.A rising edge and frequency of square wave is 200μs and 50Hz,respectively.The polarization field is in the range of 0.83 to 16.63kV/mm.Combined with the detection of crosslinking by-products of infrared spectrum,the space charge accumulation of epoxy resin is analyzed,and the influence of electric field amplitude on space charge accumulation and maximum electric field distortion rate is discussed.The results show that the space charge of epoxy near surface is dominated by heteropolar charge.It decreases obviously after 48h vacuum degassing,which is consistent with the decrease trend of the number of functional groups related to impurities such as cross-linked byproducts.It means that the cross-linked by-products is the main sources of space charge.After ions migrate to the opposite polarity electrode driven by the electric field force,heteropolar charge accumulation is obviously formed near the surface of samples.The absolute value density Pa,positive charge density P+and negative charge density p.in the whole period average phase bulk charge density all increase with the external field E with exponential n=l,which is close to the characteristic exponent n=1 of ohmic conduction.It indicates that the detection field may be in the ohmic conduction region,and the impurity ion charge is dominant as the carrier source.In the negative half period,Pa,P+and p.all show ohmic n~l,while they show an exponential increase of n between conduction and transport characteristics with an exponential 1.130 and 1.159 in the positive half period.p,of full period,p+of negative half period and p.of positive half period show obvious three-stage trial growth;there are two obvious threshold electric fields,and the maximum electric field distortion rate Omax is about 9%~17%.This may be mainly related to the dynamic balance of impurity ion charge and electrode charge quantity and distribution area of the samples at the bottom electrode side in positive and negative half-period field.