真空断路器真空度与电场电位关系研究

基于屏蔽罩电位测量真空度的方法,是真空断路器真空度在线检测方法中的一个主要研究方向。但是,目前还没有一个基于本方法的实用高真空度测量系统。为了进一步探究断路器屏蔽罩电位与真空度间的关系,本文借助于由克-莫方程建立的相对介电常数-压强间的关系,通过有限元分析工具对不同压强下的真空断路器进行二维电场分析。结果表明,屏蔽罩电位与真空度具有一定的对应关系,并可以通过真空断路器外电场电位的测量来反应;真空断路器外电场电位在压强小于10-2Pa时的变化十分微弱,而在大于10-2Pa时电位有较明显的变化。并通过实验室模拟测量实验,进一步验证了该结果的正确性。本文的分析结果给出了真空断路器外电场电位随真空度变化的规律,对基于屏蔽罩电位法在线测量真空断路器真空度具有一定的指导意义。

大型水轮发电机定子线棒绝缘参数对线棒槽部表面电位分布及电场分布的影响

应用有限元分析软件COMSOL建立了定子线棒槽部模型,仿真分析了绝缘材料参数和厚度对槽部线棒表面电位分布及电场分布的影响规律。结果表明:槽部无气隙的情况下,线棒表面电位最大值出现在防晕层上、下表面的中间位置,电场最大值位于主绝缘角落内侧;对线棒表面电位有影响的是主绝缘相对介电常数、防晕层电阻率和主绝缘厚度,在常见的范围内,主绝缘电阻率和相对介电常数基本不影响槽部电场分布;防晕层表面最大电位与主绝缘相对介电常数呈正相关,与主绝缘厚度呈负相关,与防晕层电阻率的对数值呈正相关且后期影响减弱;主绝缘相对介电常数、防晕层电阻率和主绝缘厚度对槽部最大电位具有综合影响,可通过数值分析得到三元三次多项式的回归模型。

应用有限元法计算覆冰合成绝缘子电位分布

为研究合成绝缘子的电气特性,应用有限元法计算了具有开域边界的220kV覆冰合成绝缘子的电场和电位分布。通过设置人工截断边界,将开域电场问题转化成有界域电场问题并在人工截断边界上采用渐近边界条件,利用femlab商用软件对覆冰合成绝缘子建模,计算改变冰棱的空气间隙长度及位置后的电场和电位分布,进一步研究冰棱表面水膜对电场和电位分布的影响。研究结果表明,冰棱完全桥接时电场和电位分布变化最大;冰棱在绝缘子伞裙外沿分布的位置不同,对电场和电位分布的影响也不同;水膜的出现使得覆冰合成绝缘子沿面的电场和电位分布进一步发生畸变;与传统瓷、玻璃绝缘子相比,合成绝缘子具有重量轻、强度高、耐污性能高、运行维护方便等特点。

覆冰复合绝缘子电场分布的研究

为研究覆冰复合绝缘子的电气特性,基于ANSYS有限元法建立了330 k V覆冰复合绝缘子模型,分别模拟仿真了干、湿覆冰情况下,不同空气间隙位置及冰棱长度对覆冰复合绝缘子的沿面电场、电位分布的影响,并与清洁复合绝缘子进行比较分析。结果表明:与清洁复合绝缘子相比,覆冰明显畸变了复合绝缘子的沿面电场和电位分布;当覆冰未完全桥接大伞裙间时,随着冰棱长度的增长,对沿面电位和电场分布的畸变程度越严重。当融冰过程中形成水膜时,覆冰复合绝缘子的沿面电场和电位分布进一步畸变,此时更容易发生局部放电。

500kV复合绝缘子横向覆冰现象有限元分析

雨凇覆冰严重影响输电线路的安全,绝缘子上的冰棱会导致其电场与电位分布的恶化。为探究绝缘子覆冰横向增长现象对绝缘子沿面电场电位的影响,利用ANSYS仿真软件,建立500kV复合绝缘子覆冰有限元模型。根据输电线路现场与实验室中绝缘子覆冰出现的冰棱横向增长现象,在仿真模型中改变冰棱长度、角度、位置以及横向竖直冰棱同时出现等情况,对比分析不同工况下各覆冰形态对复合绝缘子电场电位分布的影响。仿真分析表明:雨凇条件下,覆冰横向增长冰棱长度、位置的改变对复合绝缘子沿面电位电场分布的影响较小;随着冰棱铅垂角度减小,复合绝缘子沿面电场电位分布畸变增大,竖直覆冰对复合绝缘子沿面电场电位分布起主要影响。

重覆冰地区超大伞裙结构复合绝缘子的仿真及优化设计

严重覆冰时采用大小伞结构的复合绝缘子依然出现冰凌桥接现象。为防止出现冰凌桥接和覆冰闪络,开展超大伞裙结构复合绝缘子的覆冰特性研究有着重要意义。建立220 k V的超大伞裙结构复合绝缘子二维轴对称模型,并采用准静态场有限像元法进行仿真分析,对比采用不同数量的超大伞裙绝缘子在清洁和覆有干、湿冰时绝缘子的电位、电场分布。发现清洁时,超大伞裙对电位、电场分布不产生影响,在覆有干、湿冰时,超大伞裙提供的多个空气间隙,能有效改善绝缘子的电位、电场分布,特别是靠近高压端的第1个伞裙采用超大伞裙结构能改善高压端电位分布。最后结合仿真数据提出了优化后的超大伞裙结构的复合绝缘子。

综合物探在会宁县罐子峡M区块石墨矿勘查中的应用

会宁县罐子峡M勘查区地处黄土高原丘陵沟壑区,具有较好的石墨矿勘查前景。对勘查区内石墨矿成矿地质条件进行分析,选择石墨矿化有利地段开展物探工作。采取双频激电中梯剖面测量视幅频率、视电阻率及自然电场电位法测量自然电位这两种方法圈定石墨矿化异常,矿化异常表现为视幅频率高、视电阻率低和自然电位负异常较高的异常特征,在此基础上采用激电测深方法查明矿化异常体的空间展布特征;多种方法相互佐证为钻探提供依据。经钻探验证,钻遇石墨矿2层,取得了较好的勘查成果。

Effect of heartbeat perception on heartbeat evoked potential waves

Objective Early researches found that different heartbeat perceivers have different heartbeat evoked potential （HEP）waves.Two tasks were considered in our experiments to get more details about the differences between good and poor heartbeat perceivers at attention and resting state.Methods Thirty channels of electroencephalogram（EEG）were recorded in 22 subjects,who had been subdivided into good and poor heartbeat perceivers by mental tracking task. Principal component analysis（PCA）was applied to remove cardiac field artifact（CFA）from the HEP.Results（1）The good heart-beat perceivers showed difference between attention and resting state in the windows from 250 ms to 450 ms after R wave at C3 location and from 100 ms to 300 ms after R wave at C4 location;（2）The difference waveforms between good and poor heartbeat perceivers was a positive waveform at FZ from 220 ms to 340 ms after R wave,which was more significant in attention state.Conclusion Attention state had more effect on the HEPs of good heartbeat perceivers than that of poor heartbeat perceivers;and perception ability influenced HEPs more strongly in the attention state than in the resting state.

带附件系统瓷支柱绝缘子的电位和电场计算

为了研究安装附件系统对绝缘子电位和电场分布的影响,以110kV瓷支柱绝缘子为研究对象。利用有限元分析软件,分别考虑了在干燥和存在湿污层的情况下,计算并比较了有无附件系统时支柱绝缘子的电位和电场分布。最后通过干闪和污闪试验比较了有无附件系统时绝缘子的闪络电压。结果表明:在干燥情况下,安装在高压侧的附件内部电势衰减变慢,附件内部的电场降低,安装附件使得电场最大值降低了26. 6%。有湿污层存在时,第一个伞裙前端附近的场强下降最多,距离高压侧较近的其余伞裙前端附近的场强也有不同程度的下降。安装附件使泄漏电流值减少了17. 27%。安装附件之后,工频干闪电压提高了5. 9%,污闪电压提高了22. 06%。仿真结果与试验结果表现出良好的一致性。

Geoelectric response of porous media in water and grout injection processes

Significant changes in spontaneous potential and exciting currents are observed during water and grout injection in a simulated porous media. Obvious correlations between the seepage flow field and the electric field in the porous media are identified.In this work, a detailed experimental study of geoelectric field variation occurring in water migration was reported by analyzing water and grout injection processes in a simulated porous media. The spontaneous potential varies linearly with the thickness of unsaturated porous media. Very interestingly, the spontaneous potential generated in the second grout injection exhibits some"memory" of previous grouting paths. The decreases in spontaneous potential observed during grout injection is very probably due to that the spontaneous potential variations are primarily caused by electro-filtration potential, as indicated by the far larger viscosity of grout compared to that of water. The geoelectric response can be utilized to effectively identify the grouting paths in water-bearing rocks.

金属护套接地失效时电缆支架对电缆电气性能影响

通过建立用于对比的二维和三维电缆模型,用有限元静电场方法分析了两种模型下不同电缆支架对电缆各组成部分的电位和电场分布的影响。对比结果表明,二维电缆模型使电缆支架无限长的做法是错误的,同时也自证了三维模型的客观准确。金属护套接地失效时,其上感应电压相当大,支架材质影响甚微;复合材料电缆支架会造成电缆外护套压降超过其绝缘水平;不同支架材质,外护套中电场强度畸变严重的位置也不同;钢结构支架会造成外护套中电场强度异常增大,严重危及电缆的安全。复合材料电缆支架的综合性能优于钢结构电缆支架。

Electrochemical potential at the interface between carbon nanotubes and electrolyte

The dependences of electrochemical potential at the interface between carbon nanotubes and electrolyte upon temperature and electrolyte concentration are studied. Carbon nanotubes were synthesized by hot filament chemical vapor deposition with Si as the substrate. Four substances were tested: NaCl solution, KCl solution, water and alcohol. It is found that for NaCl and KCl solutions, at the interface, there is a large electrochemical potential which increases with temperature and is larger for an electrolyte of higher concentration. There is a significant field effect of carbon nanotubes with electrolyte as the gate, and the effect depends on the ionizability of the electrolyte. Such physicochemical property invests carbon nanotube a potential application in nanoelectronics.

Forward modeling for “earth-ionosphere” mode electromagnetic field

A fixed artificial source(greater than 200 kW) was used and the source location was selected at a high resistivity region to ensure high emission efficiency. Some publications used the "earth-ionosphere" mode in modeling the electromagnetic(EM) fields with the offset up to a thousand kilometer, and such EM fields still have a signal/noise ratio of 10-20 dB. This means that a new EM method with fixed source is feasible, but in their calculation, the displacement in air was neglected. In this work, some three-layer modeling results were presented to illustrate the basic EM fields' characteristics in the near, far and waveguide areas under "earth-ionosphere" mode, and a standard is given to distinguish the boundary of near, far and waveguide areas. Due to the influence of the ionosphere and displacement current in the air, the "earth-ionosphere" mode EM fields have an extra waveguide zone, where the fields' behavior is very different from that of the far field zone.

Apparently Negative Electric Polarization in Shaped Graded Dielectric Materials

By using a first-principles approach, we investigate the pathway of electric displacement fields in shaped graded dielectric materials existing in the form of cloaks with various shapes. We reveal a type of apparently negative electric polarization （ANEP）, which is due to a symmetric oscillation of the paired electric permittivities, satisfying a sum rule. The ANEP does not occur for a spherical cloak, but appears up to maximum as a/b （the ratio between the long and short principal axis of the spheroidal cloak） is about 5/2, and eventually disappears as a/b becomes large enough corresponding to a rod-like shape. Further, the cloaking efficiency is calculated for different geometrical shapes and demonstrated to closely relate to the ANEP. The possibility of experiments is discussed. This work has relevance to dielectric shielding based on shaped graded dielectric materials.

Characteristics of fulvic acid by high voltage pulse discharge plasma

High voltage pulse natural organic matter （NOM） toxic by-products. Fulvic acid discharge plasma can remove and produce no production of solution was treated by high voltage pulse discharge plasma in this paper. It was shown that： for the reason of thermolysis and oxidation, the pH and Oxidation Reduction Potential （ORP） of solution decreased gradually with the increase of peak voltage and fulvic acid solution concentration, meanwhile the temperature and turbidity of solution increased gradually. Adding hydrochlorid acid in the treatment could amplify the effect of plasma. When the concentration of NOM as the surrogate parameter, Ultraviolet Absorbancy Degree （UV254） increased slowly by the effect of plasma, while the degradation of Total Organic Carbon （TOC） was first-order reaction. The removal rate of TOC increased from 22.6% to 33.4% by high voltage pulse electrical field of 35 kv, and from 25.6% to 36.7% with the addition of hydrochlorid acid. This paper may provide some basis for the scale-up design of water treatment process by high voltage pulse discharge plasma with other technologies.

Solar wind electrons reflected by lunar electric and magnetic fields

In this paper,we report on our study of the trajectories of solar wind electrons reflected by lunar electric and magnetic fields through analysis of reflectivity and distribution under different conditions.Our calculations and simulations showed that the variations of both the magnetic field and surface potential play important roles in changing the directions of the traces of electrons.Furthermore,we were able to distinguish the changes resulting from these two variations through further analysis of the results.Thus,both the magnitude of the crustal field and the surface potential can be acquired from the data of satellites such as the Lunar Prospector.These findings could also contribute to the design and development of new devices in future lunar programs.

Electropolymerization of Ni(salen) on carbon nanotube carrier as a capacitive material by pulse potentiostatic method

The composites of poly[Ni（salen）] and multi-walled carbon nanotube （MWCNT） were synthesized by pulse potentiostatic method. The composites were characterized by field emission scanning electron microscopy, Fourier transform infrared spectra, and electrochemical impedance spectroscopy. The wrapping of carbon nanotubes with poly[Ni（salen）] varied significantly with anodic pulse duration. Variance of structure of poly[Ni（salen）] caused by anodic pulse duration affected the ability of absorption to solvent molecules or solvated ions, which was indicated by v （C≡N） intensity. The ability to store/release charge of poly[Ni（salen）] caused by redox switching was evaluated in the form of low-frequency capacitance. Correlations of chargetransfer resistance/ionic diffusion resistance with potential and anodic pulse duration were investigated.