Effect of electrode surface roughness on breakdown conditioning under non-uniform electric field in vacuum

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 R_a 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.     

Relationship between electrode surface roughness and impulse breakdown voltage in vacuum gap of Cu and Cu-Cr electrodes

The relationship between the impulse breakdown voltage of vacuum gaps and electrode surface roughness was investigated for the purpose of controlling the surface roughness on HV conductors. The roughness of mechanically polished Cu and Cu-Cr electrodes was measured with a roughness meter, and the relationship between the breakdown voltage and surface roughness was obtained for plate-to-plate gaps. The discharge-conditioning effect increased with reduction in the surface roughness. The breakdown voltage depended not only on the roughness of the cathode but also on the anode surfaces. Reducing the surface roughness was found not to be an effective way to increase the breakdown voltage for non-uniform field gaps after discharge conditioning.     

电极留边量与高压陶瓷电容器表面放电关系的研究

本文从电极边缘处瓷片表面的局部放电现象出发,采用链形等值回路,对电极边缘具有一定留边量的电容器瓷片的边缘电场进行了分析,从理论上定量解释了留边量与瓷片表面放电起始电压和边缘击穿电压的关系,进而按照能量转换关系,解释了光瓷片电容器边缘击穿电压的变化规律。     

高电压大电机绝缘系统的现代化

我国高电压大容量发电机的主绝缘系统的发展。在提高电压等级、增加散热能力、延长使用寿命、确保运行可靠性等方面达到了世界先进水平。实现了现代化。介绍了重大科研成果,指出了今后的课题方向。     

The improvement of the electrical insulation of high voltage electrical machines

Comparative parameters are presented for the electrical insulation systems of high voltage electric machines. Composite insulation materials produced by different manufacturers are studied. The influence of the structure and composition of electrical insulation materials on the main operation parameters (electric strength, dielectric losses, the mechanical characteristics, and resistance to thermal cycling) of the insulation systems of electric machines is shown.     

Effects of electrode surface morphology on electrical response ofelectrorheological fluids

In an attempt to enhance the electrical response of electrorheological (ER) fluids under DC electric field conditions, the influence of the electrode surface morphology has been studied using a rheometer in which the electrode surface was covered with a thin metallic net. The test fluids consisted of microsphere particles suspended in two insulating oils, dimethylsilicone oil and fluoridated dimethylsilicone oil. The aggregation of particles and the ER responses in these fluids revealed the effect of local changes in the electric field on the metallic net surface. It is shown that a metallic net on the electrode surface is effective for further promoting the rheological response of the ER fluid suspended in fluoridated dimethylsilicone oil. The responses appear to depend on the material properties of the ER fluids and the mesh size of the metallic net     

略谈高压开关电器的现状和发展

目前，质量较好的真空断路开断额定电流时的机械寿命是4～5万次，在保证基本技术参数和高可靠性的前提条件下，电器的外形尺寸缩小和材料消耗有所减少。据俄罗斯专家提供的不同时代生产的真空灭弧室外形、直径、重量等参数变化的曲线表明，改进触头系统的结果可成功地使灭弧室直径缩小2．5倍，质量减少3倍，俄罗斯第4代真空灭弧室的特性已赶上世界同类优秀产品。而SF6的对生态危害性正受到密切关注，对此，专家有2种不同意见：1种意见认为SR虽为氟化物，但总的投放到大气中的温室效应后果不大于0．2％，所以可不把它列入必须禁止或限制的名单中。另1种意见认为SR属于温室效应气体，真空断路器应逐步取代充气断路器。因此，世界上不少公司开展对真空断路器的研究，实现高压技术的不断进步。     

Electrode roughness effects on the breakdown of air-insulatedapparatus

The dielectric breakdown of air insulating systems is believed to be sensitive to local irregularity of the electric field which may result from the presence of defects such as contaminants adhering to electrode surfaces and surface roughness. Normally metal machining methods are used to eliminate such electrode surfaces irregularities. However, system aging and harsh operating conditions create and sustain such rough surface conditions which may, in turn, lead to the failure of insulation under the resulting enhanced electric stresses. Electrode surface roughness causes a large reduction in the breakdown strengths of gas insulated apparatus. Surface roughness leads to the existence of localized microscopic regions with local field intensities larger than the average field in the gas near the electrodes. This paper models the insulation breakdown mechanism in the presence of such surface roughness, or protrusions, taking into account their random nature which lends the problem to probabilistic treatment. In order to generalize the surface roughness effect on the dielectric withstand of air-insulated systems, surface roughness is simulated by using a random event generator. The perturbations which these protrusions inflict on the field distribution in a nearly-uniform field gap are assessed. The corresponding breakdown voltages are estimated for different patterns of surface roughness. The results are statistically formulated     

Electric field optimization of high voltage electrode based onneural network

For the insulation design of high voltage apparatus (such as gas insulated switchgear and transformers), the electric field optimization technique becomes an indispensable tool. We developed a highly efficient electric field optimization technique based on a neural network under the personal computer. Once the neural network learns the relationship between inputs and outputs, the system easily allows a target solution to be obtained. The principle of the developed optimization technique is described with the calculation example. Moreover, normalization of learning data is introduced and the applicability is expanded     

高压电器产品实施质量认证的意义和认证程序

一、高压电器产品质量认证的意义高压开关设备的质量直接关系到人身安全、设备安全和电网的安全以及供电的可靠性,严重的事故将导致人员伤亡以及大面积的停电。随着我国电力事业的蓬勃发展,电力系统高压、超高压及联网运行,其运行质量将直接影响到国民经济的发展和人民的生活水平。所以高压电器产品的正常、可靠运行直接影响到国民经济的稳步发展;高压电器产品质量的安全可靠是保证电网及发电厂正常安全运行的重要条件。对高压电器产品实施产品质量认证制造将有效促进该行业产品的质量提高。     

发电机定子线棒导线绝缘结构试验研究

对内外大型发电机定子线棒导线绝缘材料进行了分析对比,论述了导线结构和材料的技术进步,以及内均压层结构对电机绝缘技术的推进作用,分析了内均压技术、结构、导线圆角半径与定子线棒绝缘寿命、电气击穿性能的关系。     

The influence of electrode macroscopic curvature upon surface roughness effects in compressed SF6

Contents Previous theoretical studies of electrode surface roughness effects in compressed SF₆ have not included the macroscopic curvature of the electrode in the analyses. The omission of this parameter can lead to erroneous conclusions regarding the existence of a lower limit to the effect of surface roughness upon insulation strength. This aspect is examined through the application of an intersecting sphere model to the breakdown of compressed SF₆. The results indicate that, in a practical system, no lower limit exists and consequently electrode surface roughness will always lead to a reduction in the insulation strength.

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Die Einwirkung der makroskopischen Elektrodenkrümmung auf Oberflächenrauhigkeitseffekte in komprimiertem SF₆

Übersicht Bei den bisherigen theoretischen Untersuchungen der Oberflächenrauhigkeitseffektc in komprimiertem SF₆ wurde die makroskopische Krümmung der Elektroden nicht berücksichtigt. Die Vernachlässigung dieses Parameters kann zu falschen Schlußfolgerungen über die Existenz einer unteren Schranke für die Einwirkung der Oberflächenrauhigkeit auf die Isolationsfestigkeit leiten. Das Problem wird hier untersucht durch Anwendung eines aus sich schneidenden Kugeln bestehenden Modells auf den Durchschlag in komprimiertem SF₆. Aus den Ergebnissen geht hervor, daß es keine untere Schranke bei praktischen Systemen gibt; daraus folgt, daß die Oberflächenrauhigkeit immer eine Reduktion der Isolationsfestigkeit bewirkt.

     

High‐frequency voltage oscillation in transformer windings and electrical breakdown properties of interturn insulation immersed in oil at VFT voltage

Switching operations in gas insulated switchgear (GIS) can generate very fast transient overvoltages (VFTO) which propagate in the GIS with little attenuation. When a transformer is directly connected to the GIS through a gas/oil bushing, the VFTO can enter the transformer and excite the voltage oscillation in the windings. In the paper, we firstly show a resonance phenomenon due to the superposition of the traveling waves which was found in the experiments using the coil windings of a 500 kV transformer. The fundamental resonance frequency ranged at about 2 MHz, and its voltage at the interturn (turn‐to‐turn) of the coil could reach 0.25 times of the applied voltage in the worst case. Secondly, the electrical breakdown properties of interturn insulation in oil were studied, applying the unipolar and bipolar voltages with 2 MHz oscillatory frequency. The breakdown voltages at the unipolar and bipolar VFT oscillatory stresses were about 1.25 and 1.40 times higher than that at the standard lighting impulse, respectively. We discuss the experimental breakdown stresses with the ones estimated from the analysis of VFTO in the transformer windings and also show the methods to cope with the VFTO. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 45–52, 2000     

环氧包封层对高压陶瓷电容器耐电压水平的影响研究

随着高压陶瓷电容器应用范围的不断扩大，环氧树脂包封层的质量问题变得越来越突出而日益受到广泛的关注。固化残余应力是高压陶瓷电容器产品耐电压合格率降低的主要原因之一，其与电机械力的联合作用造成陶瓷－环氧界面的劣化。本文就减少残余应力，改善高压陶瓷电容器耐电压水平的不同方法进行了深入研究，提出了退火、静置和提高填料量以及对包封层增韧等技术手段。     

智能仪器在高压开关柜在线监测系统中的应用

针对高压开关柜运行可靠性要求的提高及高压开关柜在线监测系统的重要性,介绍了智能仪器在高压开关柜监测系统中的应用。并对一些重要的监测项目选出了所需的智能仪器。实践证明,以智能仪器为基础的智能高压开关柜是其今后的发展趋势。     

基于CO2传感器的高压开关柜触点超温监测仪的研制

本文以TGS4160C02传感器为基础,研制了一种新型高压开关柜触点超温监测仪。超温监测系统组成有：高分子示温片、TGS4160传感器、信号调理电路、MSP430F149单片机、报警电路以及系统软件。超温监测仪采用了温度补偿来抑制温度对传感器的影响,采用数字滤波器来提高信噪比。介绍了超温监测仪的测试条件,给出了触点温度温升曲线与CO2浓度之间的响应曲线,长时间测试结果表明,正常温度和超温情况下,监测仪的输出信号具有明显不同的特征,且具有良好的稳定性。     

高压电器远程监控技术的应用与发展

从高压电器设备的发展出发,结合现场总线技术以及设备远程监控技术详细的介绍了高压电器远程监控技术,给出了高压电器远程监控技术成功应用实例说明了其独特的优势。最后展望了高压电器远程监拉技术的应用前景和发展趋势。     

高压电器智能化与配电网保护自动化研究

随着国家电网的快速发展和电气设备的智能化发展,电器用电结构与过去相比发生了很大改变。配电网自动化技术研究已成为我国目前主要研究方向之一。就现阶段而言,如何将智能化与自动化有机结合而实现配电系统一体化是目前的主要研究课题。本文分析了高压电器智能化发展现状,探讨了高压电器配电自动保护系统的主要构成,并对高压电器智能化与配电网保护自动化技术目前所存在的问题和应对措施进行了研究。