交联聚乙烯试样中空间电荷输运特性的数值模拟

挤塑型交联聚乙烯(XLPE)高压直流电缆绝缘中空间电荷的积聚会造成局部场强畸变,导致材料的绝缘性能下降。电缆内导体的热效应在绝缘层产生的温度梯度会进一步影响电荷行为,纳米颗粒改性是抑制空间电荷的一种有效措施,但抑制作用具体如何实现,尤其是对于微观层面载流子输运过程的影响规律还需深入分析。试样内空间电荷的数值仿真可以探究各种微观粒子之间的相互作用和演化过程,因此文中基于载流子抽出受限的双极性电荷输运模型,对温度梯度下的电荷行为,深陷阱与浅陷阱对于载流子迁移过程的影响进行了研究。结果表明：低温侧会因抽出受限而积聚异极性电荷,深陷阱会限制载流子输运且深陷阱作用存在瓶颈,随着迁移率增大,电荷分布由同极性变为异极性分布,当迁移率足够大时,异极性电荷不再增长甚至开始降低。     

基于交流电场下空间电荷检测技术的变压器绝缘纸老化研究

针对在运20年的发生绝缘故障的110kV变压器,在交流电场下利用高分辨率的空间电荷检测装置进行了故障诊断,并通过变压器解体检查验证了利用空间电荷检测技术进行油纸老化测量的可行性.     

热老化下双层聚酯薄膜空间电荷特性的试验与数值仿真研究

双层电介质广泛应用于高压电气设备绝缘系统中,由此引入的空间电荷积聚和局部电场畸变问题已得到普遍关注。为揭示界面空间电荷特性及其影响影响因素,文中以热老化处理（130℃）的双层聚酯薄膜（PET）为研究对象,采用电声脉冲法（PEA）测量技术对不同热老化程度双层介质的空间电荷特性进行研究,基于测试结果从3个方面对双层介质表面态特性进行表征,建立改进的双极性电荷输运模型（BCT）,模拟空间电荷的动态演变过程,揭示了表面态对电荷特性的影响规律。试验结果表明：随着老化时间增加,界面电荷密度先增加后减小,界面区域以电子性陷阱为主,但该区域电子和空穴陷阱呈现非对称特性。仿真结果表明：表面态对界面电荷行为有重要影响,介质表面陷阱深度、密度及其分布范围的增加导致界面电荷的积聚更加严重。     

工频双极性方波电场下环氧树脂的空间电荷特性EI北大核心CSCD

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。     

基于双极性载流子输运模型的聚酰亚胺薄膜空间电荷数值模拟

聚酰亚胺（PI）薄膜因其优异的电气性能广泛应用在电力设备中,但空间电荷会在PI薄膜内部积聚导致其电气绝缘性能劣化。为了获得绝缘性能优异的PI薄膜,需要进一步研究薄膜内部空间电荷动态积累和迁移过程,优化其内部结构。本研究基于双极性载流子输运模型,分析了PI薄膜在直流电压下空间电荷的分布,探讨了电场强度与温度对PI薄膜内部空间电荷分布特性的影响。结果表明：随着施压时间的延长,薄膜内积聚的空间电荷增多,施压180 min后,阳极和阴极分别积聚了0.635 C/m3和-0.712 C/m3的电荷,且空间电荷的存在使薄膜内部电势发生严重畸变。电场强度和温度的升高让电荷获得更多能量去克服界面势垒并注入到薄膜内部,使薄膜内部积聚的空间电荷增多,电场畸变更严重,在308 K温度下,薄膜电场畸变率高达0.968%。在强电场和温度场中,由于电荷迁移速率随温度和电场强度增高而变快,空间电荷在PI薄膜内部的分布更加复杂。     

聚酰亚胺薄膜中电荷输运机理和空间电荷特性

通过测量比较耐电晕型和普通聚酰亚胺薄膜空间电荷积聚的阈值电场,分析温度对空间电荷分布的影响,以此来研究聚酰亚胺薄膜中电荷输运机理和空间电荷的特性.试验结果表明:耐电晕型聚酰亚胺薄膜空间电荷积聚的阈值场强高于普通聚酰亚胺薄膜,纳米粒子的加入有效地提高了耐电晕型薄膜的介电性能.此外,温度的升高促进电极发射电荷,增大电荷的能量和电导率,使得空间电荷的数量不断地增加,入陷的位置逐渐向介质体内移动,这与聚酰亚胺薄膜绝缘老化、击穿关系密切,是空间电荷的重要特性.     

温度梯度效应对油纸绝缘材料空间电荷分布特性的影响

针对换流变压器及直流套管中油纸绝缘系统存在的内外温度不同的温度梯度效应对油纸绝缘中空间电荷分布的影响,利用电声脉冲法(PEA)研究了不同温度差下(△θ=0～40c),在场强分别为10～40 kV/mm时单层油纸中空间电荷特性及场强分布.实验结果表明:在各个电压及温度梯度下异极性电荷始终存在,这表明油纸绝缘中的杂质电离在...     

极性反转条件下基于双极性载流子-离子混合输运模型的XLPE空间电荷特性研究

直流电缆在运行时需承受极性反转的电压,这会使得绝缘内部积累的空间电荷增加,进而可能引起绝缘破坏。同时在绝缘材料实际生产过程中引入的交联副产物等杂质解离产生的离子电荷会加剧电荷的积累。因此本文对传统双极性载流子输运模型进行改进,考虑杂质带电离子的影响,利用改进后的输运模型模拟交联聚乙烯（XLPE）内部空间电荷在电压极性反转期间的分布,研究极性反转时间和电场强度对电荷分布的影响机理。结果表明：在满足电压反转前后空间电荷分布基本呈镜像分布的基础上,引入离子电荷会增大两电极附近稳态时积聚的异极性电荷量;电压反转时间越长,两电极处的界面电荷峰值下降的越多,两电极附近的空间电荷变成相反极性的电荷量也越多,即反转完成时电荷分布更接近于反转稳定后的情况;在相同极性反转时间、不同电场强度下,电荷分布规律基本相同,场强越高,各处积累的电荷量越多。     

Influence of oil aging on the space charge dynamics of oil‐immersed paper insulation under a DC electric field

The formation of space charge in oil/paper insulation system can lead to material degradation in the region of high electric field. Therefore, it is important to understand the factors that affect space charge formation in oil/paper insulation system. In this paper, the effect of oil aging on space charge dynamics in oil/paper insulation system is investigated using the pulsed electroacoustic (PEA) technique under a DC electric field at room temperature. The ultraviolet/visible (UV/vis) spectrum of the oil shifts to longer wavelengths, and the oil acidity increases as the aging time increases. It has been found that the oil property has a significant effect on the space charge distribution in the oil/paper insulation sample. The more the deterioration of the oil, the larger amount of negative and positive charges accumulated in the bulk of the oil/paper insulation sample. The total amount of slow moving charges, the surface trap energy density, and the electric field distortion of the oil/paper insulation sample increased with the degree of deterioration due to oil aging. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Study on the properties of space charge and breakdown for epoxy–paper composites

The properties of space charge and breakdown in epoxy/paper composites are studied in this paper. The results show that the breakdown voltage of the epoxy/paper composite is lower than that of the epoxy under AC voltage but is higher under DC voltage. In order to explain this phenomenon, the space charge behavior is investigated. In epoxy/paper composites, the space charges easily accumulate at the epoxy/paper interface at low fields, and the electric field distribution is highly deformed. However, the amount of interface charges decreases with increasing voltage, leading to a more uniform field distribution in the composites. This behavior is different from that of the pure epoxy, resulting in the different breakdown properties of pure epoxy and epoxy/paper composites. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

空间电荷及金属颗粒对换流变阀侧套管的电场分布影响

换流变压器阀侧套管承受交、直流复合电压,对套管的性能和质量有严格的要求。直流电压下,不同介质界面处空间电荷积聚会引起局部电场的畸变,金属颗粒的存在也会大幅提高局部场强,二者均会降低套管的绝缘性能。文中根据换流变压器阀侧套管的结构,采用有限元分析软件,建立了阀侧套管的仿真模型,分析了加入空间电荷后不同类型电压下套管的电场分布以及金属颗粒对局部电场的影响。结果表明,直流电压下介质界面处空间电荷更容易积聚,交直流复合电压下空间电荷能够引发套管内部局部电场的畸变。与交流电压相比,直流电压下金属颗粒对局部电场的畸变程度影响更大,在SF₆气体中金属颗粒对电场畸变程度的影响大小与其所在位置的关系不大。     

天然酯绝缘油-纸界面的多分支流注放电仿真

油纸界面的局部放电是油浸式变压器中油纸绝缘失效的主要原因之一。本文在多分支流注放电数值模型基础上通过进一步考虑油纸界面的电荷输运特性,构建了油纸绝缘系统中的多分支流注放电模型,并利用有限元法分别对天然酯绝缘油/纸介电常数配比、针电极与纸板的间距影响下的沿面放电特性进行了研究。结果表明,针电极与纸板的间距及油/纸介电常数配比均会显著影响流注分支;针电极与纸板的间距越小,油纸界面处的流注分支间的抑制越明显,油纸界面的流注对z-轴流注的影响更显著;当绝缘油介电常数相比纸板大时,流注在油中的发展和分支更为显著,反之则流注更易沿纸板表面发展及在油纸界面聚集电荷。     

Some factors for the space charge formation in polyethylene

Information on space-charge behavior in thick insulated samples aids in understanding the dc characteristics of polymer-insulated dc cables. The pulsed electroacoustic method is used to investigate several space charge formation factors in 2 mm-thick polyethylene (PE). The following results were obtained. For measurement factors: (1) A polymeric semiconducting electrode provides a more accurate measurement than does a metal electrode as a result of better matching of acoustic impedance with PE. (2) Within a dc electrical stress range of several tens kV/mm, the space charge distributions under and after dc voltage application are almost the same; this is due to a comparatively long time of space-charge decay. (3) The space-charge distribution of a plate sample agrees with that of a cable sample having the same insulation thickness. For insulating material factors: (1) The amount of space charge in crosslinked polyethylene (XLPE) is much larger than that in low-density PE (base of XLPE). The space charge of XLPE continues to increase even after dc voltage application (24 h); that of LDPE reaches equilibrium with a few hours. (2) The aforementioned space charge difference between XLPE and LDPE is assumed to be caused by ionic impurities in XLPE, not by the additives themselves (acetophenon and cumylalcohol as byproducts of cross linking and antioxidant).     

Transient phenomena of space charge distributions in polypropylene laminated paper

In a multilayer insulator made of two or more materials with different dielectric constants and conductivities, internal space change accumulates at their interfaces. If the local field is increased by the accumulated charge, the electric durability of the insulator should be decreased. In this paper, we describe the space charge accumulation measured when oil-impregnated PPLP (polypropylene laminated paper), which consists of three layers, kraft paper, polypropylene (PP), and kraft paper, was subjected to a strong dc electric field. The experimental results suggest that internal space charge accumulates at both surfaces of a PP layer and that the electric field in the kraft paper layers disappears. © 1998 Scripta Technica, Electr Eng Jpn, 124(1): 1–6, 1998     

基于改进电声脉冲测试系统的油纸绝缘混合体系空间电荷动态行为特性

目前国内外关于油纸绝缘介质空间电荷特性的研究全部基于油浸绝缘纸,且已有的电声脉冲测试系统无法实现对油隙与油浸纸组合而成的混合体系的空间电荷特性的测试。通过采用改进的电声脉冲测试系统首次对油隙与油浸纸板组合而成的混合体系的空间电荷动态行为特性进行研究,分析空间电荷积聚对油纸混合体系内部电场分布的影响。研究发现油纸绝缘界面处及油浸绝缘纸内部积聚的空间电荷和电场畸变程度与绝缘油和油浸纸板的电导率关系很大。由绝缘油劣化导致油纸绝缘系统的电导率提升更易引起油浸纸内部场强严重畸变,油浸纸内部最大场强约达到平均场强的2.5倍。而由油浸纸电导率增大引起的油纸绝缘系统的电导率提升减轻了油浸纸内部的电场畸变程度,但电荷快速迁移会导致介质热效应显著也易诱发击穿。消除绝缘结构界面引起的空间电荷积聚效应、限制空间电荷在绝缘介质内部的快速迁移或使电荷在介质内部分布更加均匀,从三方面出发将有助于抑制空间电荷的危害。     

Ways to calculate electric fields in traction electric motor insulation by equivalent charge method

A procedure permitting one to calculate the electric fields in multilayer insulation based on the equivalent charge method is presented. Consideration of the new algorithm shows its fast response and proper accuracy.     

Measurement of space charge distributions in PLZT using Kerr effect

Kerr effect technique is an optical measurement technique used to determine space charge distributions of a dielectric liquid under applied electric stress. In other words, such measurement can be used to study the conduction mechanisms of a dielectric liquid, such as charge injection threshold, bulk electric field stress, and aging. In this study, an instrument was set up to measure the absolute value of the electric field distributions in lead–lanthanum–zirconium–titanium (PLZT). PLZT was selected for the study of the instrumentation because the material has a high Kerr constant. In the experiment, charge injection threshold and bulk field strength of PLZT were measured under low applied voltages. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

不同含水量油纸绝缘热老化过程中的空间电荷特性研究

水分会导致油纸绝缘电气性能下降并加速老化,但是水分对油纸老化过程中空间电荷特性的影响鲜有报道。本文利用电声脉冲(PEA)法研究了不同老化阶段、不同含水量油纸中的空间电荷特性,结果表明当含水量较低时,增加含水量可以加速空间电荷到达稳态,但是进一步增加含水量反而会减速;老化初期的油纸主要以异极性电荷积聚为主,而随着老化程度的加剧,逐渐演变为同极性电荷注入。随着含水量的增加,需要更长的老化时间电荷注入类型才会发生变化,继续增大含水量将加速注入类型的转变。分析认为水分一方面会加速老化,加剧空间电荷积聚,另一方面会加快或减缓空间电荷到达稳态的过程,所以电荷注入类型会发生转变,转变时油纸中的空间电荷会很快到达稳态,阳极附近空间电荷积聚变少,电场畸变程度小。