共查询到20条相似文献,搜索用时 491 毫秒
1.
Takanori Yasuoka Tomohiro Kato Katsumi Kato Hitoshi Okubo 《Electrical Engineering in Japan》2011,175(2):21-28
Electrode conditioning is a very important technique for improvement of the insulation performance of vacuum circuit breakers (VCBs). This paper discusses the spark conditioning mechanism under a nonuniform electric field, focusing on the pre‐breakdown current. We quantitatively evaluated the spark conditioning effect by analyzing the pre‐breakdown current based on the Fowler‐Nordheim equation. The field enhancement factor β was found to decrease with increasing breakdown voltage at the beginning of the conditioning process, and finally became saturated with the saturation of the breakdown voltage. In addition, in the case of a nonuniform field, we found that β on a high‐voltage rod electrode after conditioning varied according to the electric field strength on the rod electrode. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 175(2): 21‐28, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21059 相似文献
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针对特高压直流输电线的地面电场和离子流密度的计算问题,采用有限元-积分方法,对双极离子流场的控制方程进行求解,同时还对空间电荷密度初值进行了改进。通过计算,发现该方法能较快地获得稳定的数值解。通过采用该方法对±400kV的直流线路进行了比对计算,验证了该算法的有效性。将该方法应用于实际的±800kV直流输电线路,对地面合成电场和离子流密度进行了计算,分析了导线对地高度、极间距、正负极起晕情况不同以及避雷线对地面合成电场和离子流密度的影响。结果显示随导线高度升高和极间距减小,地面的最大电场强度和离子流密度随之减小。在正、负极起晕不同时,负极导线下面的合成电场和离子流密度的最大值比正极大。计算中,考虑避雷线会增大地面的合成场强和离子流密度,但是不明显。 相似文献
3.
Eiji Takahashi Akinori Ebe Kiyoshi Ogata Yoshinori Hayashi Daisuke Makabe Mototaka Sone 《Electrical Engineering in Japan》2000,131(4):11-18
Two different surface treatments (mechanical polishing, thin film deposition) were performed on cathode surfaces, and the field emission currents from the cathodes were measured with a microchannel plate. In order to discuss the relationship between the breakdown voltage and prebreakdown current in the vacuum gap, the breakdown voltage was measured after field emission measurement. The V–I characteristics of the field emission and breakdown voltage were influenced by surface treatment, and the breakdown voltages of mechanical polished cathodes were lower than those of the thin film deposited cathodes. It was found that the probability of breakdown increased when the field emission current reached 10–11 A. Atomic force microscope (AFM) measurements showed numerous protrusions on the cathode surface in the case of thin film deposition treatment, but we estimated by the finite element method that these protrusions make the field enhancement effect low. It was inferred that the breakdown voltage in vacuum gaps could be increased by the thin film deposition method. © 2000 Scripta Technica, Electr Eng Jpn, 131(4): 11–18, 2000 相似文献
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Hidenori Mimura Kazufumi Shiozawa Yoichiro Neo Morihiro Okada Masafumi Takahasi Gen Hashiguchi 《IEEJ Transactions on Electrical and Electronic Engineering》2007,2(3):272-277
Sputter‐induced carbon nanoneedle field emitters and Si electron‐transparent films have been developed for electron‐beam‐pumped light sources. The sputter‐induced carbon nanoneedle field emitters exhibited a stable electron emission of 0.1 mA at an average field of 13 V/µm. The 1.5‐µm thick Si electron‐transparent films achieved an electron transmittance of about 60% at an acceleration voltage of 27 kV. An electron‐beam‐pumped light source was demonstrated from the excitation of N2 gas, and a N2 gas spectrum was clearly observed. The increase of the beam current is important for increasing the light intensity. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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直流离子流场的有限元迭代计算 总被引:1,自引:3,他引:1
针对高压直流输电线下方地面处电场强度及离子流密度的问题,采用有限元迭代方法求解了双极离子流场控制方程。将正负极电流连续性方程合并,减少了计算的复杂度。利用圆筒电极问题,将该文计算结果与解析解进行对比,验证了算法的有效性。将方法应用于200kV直流输电线路模型的计算,并与文献测量结果进行对比,计算结果与实测结果较符合,认为误差主要与测量环境有关。利用该文方法计算了实际±500kV直流输电线路离子流场问题,并分析了导线对地高度、极间距变化时地面电场强度和离子流密度的变化情况,结果显示,随导线高度升高和极间距减小,地面处最大电场强度和离子流密度随之减小。 相似文献
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《IEEJ Transactions on Electrical and Electronic Engineering》2017,12(1):16-23
Ion mobility is one of fundamental parameters to describe the motion of ions in an electric field and a significant quantity to calculate the ionized field and ion current density of ultrahigh‐voltage direct current (UHVDC) power lines. This paper presents a measurement method for atmospheric ion mobilities in a DC corona discharge. An apparatus with coaxial cylindrical electrodes is designed and utilized. A vibrating electric field meter is employed to measure the ionized field of the electrode. Experimental results show that under atmospheric conditions, the average positive and negative ion mobilities are 1.76 × 10−4 and 1.88 × 10−4m2·V−1·s−1, respectively. The proposed method is compared with previous works of others. The impact of fluctuations of the measured ionized field and ion current density on the results of ion mobilities is also analyzed. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
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Maglaras A. Topalis F.V. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2009,16(1):32-41
This paper investigates the influence of grounding on the field distribution and on the dielectric behavior of small rod-plate and rod-rod air gaps. This effect can be attributed to the grounding of one electrode. In the different arrangements with one electrode grounded or with the electrodes symmetrically charged the experimental results of the corona and breakdown are recorded and compared to the simulation results of the field distribution. It is resulted that the grounding influences significantly the electric field distribution, the dc corona and the dc breakdown. The field is less inhomogeneous in grounded rod - plate air gaps and in rod-rod air gaps with symmetrically charged electrodes, and consequently the values of the corona onset and the breakdown voltage are higher. In longer air gaps the corona current influences the field distribution and consequently the dc breakdown. The effect of grounding on the breakdown is weakened when the dc polarity of the voltage is negative, otherwise it is enhanced. In air gaps with lengths > 3 cm (negative dc polarity) or >8 cm (positive dc polarity) it is overlapped by the effect of the corona current. Relations between the field strength, the corona current, the corona onset and the breakdown voltage arise. The principle of action-reaction is valid. 相似文献
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Kato K. Fukuoka Y. Saitoh H. Sakaki M. Okubo H. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(3):538-543
Breakdown (BD) characteristics in vacuum are strongly dependent on the electrode surface conditions, such as surface roughness. However, there is little known concerning the details of the relationship between the surface roughness and BD conditioning effect. In practical application, it is important to clarify how the surface roughness affects the breakdown conditioning characteristics, especially for the non-uniform field configuration. This paper discusses the effect of surface roughness on breakdown conditioning characteristics under non-uniform electric field in vacuum under applications of negative standard lightning impulse voltage. For this purpose, we examined the BD conditioning of a rod-to-plane electrode made of SUS304 and Cu-Cr. The surface roughness of Ra is controlled from 0.3 to 2.5 mum. Experimental results revealed that the enhancement of surface roughness of electrodes increases the number of BD to complete the conditioning effect. We explained the results from the observed results of the electrode surface. Consequently, we could clarify the effect of surface roughness on the conditioning effect under non-uniform electric field in vacuum quantitatively. 相似文献
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Koppisetty K. Kirkici H. Schweickart D.L. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(3):553-559
In general, power devices and systems operating in vacuum or space environment are more susceptible to partial discharges, corona, or volume discharges due to the partial vacuum conditions. Additionally, high frequency operation of a power system is a contributing factor in lowering the breakdown voltage of insulation. In this paper we present our studies on the breakdown characteristics of helium operating in DC and 20 kHz AC field in partial vacuum, for a point-to-point and point-to-plane electrode configurations. Breakdown voltage as a function of pressure in the range of 27 to 400 Pa (0.2 to 3 torr) for both the DC and 20 kHz AC cases is presented. Voltage and current waveforms along with the optical emission waveform of the breakdown events are also presented. A variable DC power supply for DC and an in-house built variable DC-offset-AC power supply for the high frequency breakdown experiments are used. A high voltage probe and a Pearson current sensor are used for the voltage and current detection, and a photo-multiplier-tube with a digital pico-ammeter and a video camera are used for the optical signal detection of this set-up. The breakdown voltage as a function of pressure for both the AC and DC experiments, along with voltage breakdown waveforms for both electrodes are presented. 相似文献
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Takuma T. Kawamoto T. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(3):566-571
The field singularity occurs at an edge point where wedge-like interfaces of dielectrics meet. This phenomenon is well known as "Takagi-effect" or "triple-junction effect" in the cases of two dielectrics. Its significance is twofold; (1) the negative phenomena of possible discharge or breakdown inception, and (2) the positive application of the field enhancement to field emission or electron beam generation in vacuum. This paper describes the analytical expression which gives the exponent of the field singularity in three dielectric media, and applications of this expression in various simple conditions. The analytical expression is also compared with the value given from the numerical field calculation. 相似文献
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接地网模拟计算对工程接地网设计有着重要的指导作用。接地阻抗、接触电压、跨步电压是接地网设计的重要指标, 根据这些接地网参数来判断接地网设计的合理性。时变激励下的接地网模拟计算能够较为准确地求得接地网上的电压分布, 从而进行变电站内电子设备之间的电磁干扰分析。基于时变场中电流元在分层媒质中产生的电磁场问题的研究, 利用接地网导体棒表面沿轴向电场强度分量连续的边界条件, 列写了以各段导体棒电流为未知量的方程组, 从而求得各段导体电流, 进而得到各接地网参量以及接地网电压分布。采用该方法编制的一套软件可以得到接地网的接触电压、跨步电压、接地阻抗及其频率特性、接地网各点和接地网周围各点电压, 在计算效率和计算精度上能够满足实际工程设计的需要。 相似文献
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Eiji Takahashi Akinori Ebe Kiyoshi Ogata Shigehiro Komuro Hideo Mitsui Mototaka Sone 《Electrical Engineering in Japan》2001,136(3):10-18
In order to discuss the characteristics of field emission sites, an aging effect on field emission current was measured in terms of cathodes subjected to two different surface treatments: mechanical polishing and thin film formation. A field was applied to the test cathodes up to an emission current of 10–11A. Such measurement was repeated 50 times. It was found that the field emission current decreased with increasing number of test runs, and the amount of such degradation was larger for the case of mechanical polishing than for thin film formation. The field enhancement factor β evaluated by F–N plot was kept constant with increasing test runs for the mechanical polishing, while β increased with increasing test runs for the thin film formation. It was estimated by means of emission site observation that the emission sites on the mechanically polished cathode were related to the adsorption gases or weakly attached foreign particles, while the emission sites on the thin film formation cathode were related to the metallic whiskers. The characteristics of emission sites could be controlled by the surface treatment, especially by the thin film formation. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 10–18, 2001 相似文献
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由于交、直流并行输电线路周围电场既有直流分量,又有交流分量,为混合电场,传统的仪器无法直接开展测量工作。为此,在分析现有直流线路地面电场测量装置(旋转伏特计)、地面离子流密度测量装置(离子流板)测量原理的基础上,研究了交、直流混合电场下已有测量设备输出结果的频谱特征,建立了交流和直流电场与测量结果频谱的对应关系,从而提出了交直流并行输电线路下同时考虑直流和交流分量的地面电场和离子流密度测量方法。在缩尺模型下的实际测量和分析表明,所提出的交、直流混合电场下地面电场和离子流密度的直流和交流分量测量方法是有效的。 相似文献
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AbstractAl doped and Cu doped ZnO NRAs/Graphene composite material are synthesized by introducing the concentrations of 0%, 2%, 4%, 6%, 8% using hydrothermal method, and their structure and morphology are characterized by XRD, EDS and SEM, XPS. The results show that Al:6% doped and Cu:4% doped ZnO/Graphene nanorod array have the best crystal quality and morphology compared to other concentrations of doped samples. Other than that, the field emission performances of Al:6% doped and Cu:4% doped ZnO NRAs/Graphene are measured. The turn-on field and field enhancement factor of Al:6% doped ZnO NRAs/Graphene are 1.51?V/mm and 11264. The turn-on field and field enhancement factor of Cu:4% doped ZnO NRAs/Graphene are 1.80?V/mm and 10076. It is found that the field emission performance of Al: 6% doped ZnO NRAs/Graphene is higher than the sample with doped Cu, which indicating that Al-doped ZnO NRAs/Graphene might have promising applications for various field emission devices. 相似文献
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高压电场中金属丝段的电爆现象 总被引:7,自引:5,他引:2
金属丝电爆是制备超细粉的一种新方法,为了解决通常所采用金属丝与电极接触后通入大电流的电爆方法容易发生电极烧蚀这一问题,开发了高压电场中金属丝段与电极非接触电爆的设备。通过改变电极间距、金属丝长度和电场电压,进行了系列高压电场中金属丝段电爆试验。结果表明,在高压电场中电极与金属丝的端部发生气体放电,将大电流导入金属丝段而发生电爆,可减轻对电极的烧蚀;由于金属丝段的端部与电极之间的等离子体旁路作用,金属丝段的端部残留0.5~2 mm长的金属丝不发生电爆;适于制备粉末的电场中金属丝段电爆的工艺条件是,电场电压为6、7、8 kV时,与之匹配的电极间距与丝长之差的范围分别为:1.8~4 mm、2.2~5.8 mm和3.2~8 mm。 相似文献
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This paper describes the influence of space charge on the growth of an electrical tree which is an important factor of the dielectric breakdown in polyethylene-insulated power cables. Polyethylene and ethylene vinyl-acetate copolymer with a semi-conducting needle were used as the treeing specimens. The statistical analysis showed that the growth rate and the unbalance of positive and negative partial discharges increased as the vinyl-acetate content increased, and that the growth per cycle decreased with the increase in frequency. A model of the tree growth accompanied by the space charge behavior was proposed considering the above experimental results. The tree growth is considered to be caused by the dielectric breakdown due to the field enhancement at the tree tip during the positive half cycle of the applied voltage, the field enhancement being due to residual negative space charge injected during the previous negative half cycle. The negative space charge in polyethylene would be mainly supplied through the partial discharge inside the tree. 相似文献