为了通过空间电荷脱陷行为反映电缆XLPE绝缘老化程度,提出了一种从XLPE绝缘介质的极化-去极化电流(polarization and depolarization current,PDC)中提取出脱陷电流ide-trap的方法与相应的陷阱电荷密度Anτn和陷阱深度τn的计算方法。...为了通过空间电荷脱陷行为反映电缆XLPE绝缘老化程度,提出了一种从XLPE绝缘介质的极化-去极化电流(polarization and depolarization current,PDC)中提取出脱陷电流ide-trap的方法与相应的陷阱电荷密度Anτn和陷阱深度τn的计算方法。通过从脱陷电流中提取出参数τn和Anτn,并利用脱陷电流曲线作出ide-trapt^lnt曲线(t为时间),表征了XLPE中陷阱电荷密度与陷阱深度。在分别改变PDC测试时的极化场强、空间电荷注入时长和试样热老化程度后计算试样中陷阱电荷密度和陷阱深度,结果表明:PDC测试中较高的极化场强更能促进深陷阱中电荷逃逸;随着空间电荷注入时长增加,中等深度陷阱相较于浅陷阱和深陷阱更容易积聚电荷;XLPE的热老化首先经历重结晶阶段,后进入热氧老化阶段,结晶度变化导致XLPE中陷阱数量先增加后减少,而在整个热老化过程中陷阱深度逐渐加深。研究结果表明,基于极化-去极化电流测试可对XLPE中陷阱电荷的脱陷特性进行分析,通过参数τn、Anτn和ide-trapt^lnt曲线可反映XLPE中陷阱电荷密度及陷阱深度并表征XLPE绝缘的老化程度。展开更多
The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influenc...The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.展开更多
文摘为了通过空间电荷脱陷行为反映电缆XLPE绝缘老化程度,提出了一种从XLPE绝缘介质的极化-去极化电流(polarization and depolarization current,PDC)中提取出脱陷电流ide-trap的方法与相应的陷阱电荷密度Anτn和陷阱深度τn的计算方法。通过从脱陷电流中提取出参数τn和Anτn,并利用脱陷电流曲线作出ide-trapt^lnt曲线(t为时间),表征了XLPE中陷阱电荷密度与陷阱深度。在分别改变PDC测试时的极化场强、空间电荷注入时长和试样热老化程度后计算试样中陷阱电荷密度和陷阱深度,结果表明:PDC测试中较高的极化场强更能促进深陷阱中电荷逃逸;随着空间电荷注入时长增加,中等深度陷阱相较于浅陷阱和深陷阱更容易积聚电荷;XLPE的热老化首先经历重结晶阶段,后进入热氧老化阶段,结晶度变化导致XLPE中陷阱数量先增加后减少,而在整个热老化过程中陷阱深度逐渐加深。研究结果表明,基于极化-去极化电流测试可对XLPE中陷阱电荷的脱陷特性进行分析,通过参数τn、Anτn和ide-trapt^lnt曲线可反映XLPE中陷阱电荷密度及陷阱深度并表征XLPE绝缘的老化程度。
基金Project supported by National Basic Research Program of China （973 Program） （2014 CB239501, 2011CB209400）, National Natural Science Foundation of China （NSFC 50877040）.
文摘The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.
