电晕放电对声发射式绝缘子污秽放电监测影响的研究

对电晕放电和污秽放电声发射信号的特征进行了分析研究。利用两者放电声发射在相位与强度上的差别,提出了识别电晕放电和污秽放电声发射信号的新方法,消除了电晕放电对污秽放电声发射信号的干扰,解决了基于声发射技术的绝缘子污闪在线监测受电晕放电影响的技术难题。     

线路绝缘子污闪事故原因分析及预防措施

从送电线路安全运行的角度出发,结合石嘴山地区送电线路在运行过程中发生污闪事故的实际情况,就绝缘子污闪事故原因和特点、污秽等级划分、资料收集和管理进行分析,并提出预防措施.目的是保证送电线路的安全运行.     

表面电荷积聚对绝缘子沿面闪络影响的研究

通过对典型绝缘子表面电荷分布特点的分析，研究了表面电荷与放电起始间的关系。研究表明在表面电荷作用下绝缘子沿面闪络起始电压会发生变化。对110kV三相共箱式GIS绝缘子的闪络实验表明，表面电荷可使绝缘子沿面闪络电压下降23．4％。对位移电流作用下的绝缘子沿面闪络先导发展模型进行改进，补充了表面电荷对该模型的影响。指出表面电荷产生的附加电场会影响流注电晕内部正负电荷的分离速度及放电的进一步发展。     

Effect of insulator diameter on AC flashover voltage of an ice-covered insulator string

The effect of the diameter of an insulator covered with ice on its flashover voltage was investigated. The insulator diameter was simulated and varied by controlling the width of a layer of ice artificially accreted on a short string of 5 IEEE standard units. The 50% withstand voltage (V/sub 50/) was experimentally determined using the method described in IEC 60507. The results show that the V/sub 50/ decreases as the width of the ice layer increases. Moreover, a mathematical model for predicting the critical flashover voltage of ice-covered insulators is proposed, and is validated against the experimental results. The model is then applied to ice-covered industrial insulators with different diameters yielding good concordance between the results from the model and the experimental ones.     

Effect of insulator profiles on DC flashover voltage under pollutedconditions. A study using a dynamic arc model

From field experience and laboratory tests, it has been observed that the contamination flashover voltage of insulators used on DC lines is more influenced by geometry (diameter and profile) than those used on AC lines. Presented in this paper are the results and analysis of a study of the effect of insulator shapes on the DC contamination flashover voltage. A dynamic arc model is used for this purpose. The salient feature of the model is that it takes into account the geometry of the insulator at every instant of the arc propagation, and thus includes the role of geometry in the contamination flashover process. A variety of porcelain cap and pin insulator geometries that are widely used in practice have been evaluated using this model. Nonuniform pollution distribution on insulators, which is more representative of field conditions, has also been considered, and its effect on the flashover voltage has been evaluated for the various geometries. Results are in good agreement with the experimental findings. Use of the model as a design tool to select type and number of insulators for HVDC transmission lines has been illustrated     

盆式绝缘子存在自由金属颗粒时的电场分析及其对沿面闪络的影响

为研究气体绝缘全封闭式组合电器(GIS)中盆式绝缘子表面存在自由金属颗粒时的沿面电场分布及其对沿面闪络的影响,建立了800k V盆式绝缘子三维结构模型,采用有限元法对盆式绝缘子存在大小、位置及形状不同的自由金属颗粒时分别在工频电压、雷电冲击电压及快速暂态过电压(VFTO)作用下的电场进行了分析。给出了不同情况下盆式绝缘子的沿面电场分布、沿面法向和切向电场强度分布曲线及电场强度最大值。通过与不存在缺陷时的闪络场强作对比分析,为GIS的绝缘设计提供参考。     

Vacuum insulator flashover mechanisms, diagnostics and designimplications

This paper presents an approach for obtaining science-based answers to practical vacuum device problems. The question “How to translate scientific knowledge to design and operation practice” is rephrased to the more productive question “What research activities are required to provide science-based answers to practical problems!” Such activities involve the study of operational mechanisms in realistic, geometries with the help of appropriate diagnostics. Within this framework, recent research developments on vacuum insulator flashover are reviewed, with emphasis on the implications for device performance and design. Secondly, an overview is given of recent research activities performed at the Eindhoven University of Technology. By studying the relationship between flashover mechanisms and insulator performance, and the relationship between insulator performance and design, we aim at improved device performance, the formulation of guidelines, and the development of device diagnostics, for dc and ac vacuum devices     

Effect of climatic conditions on contamination flashover voltage ofinsulators

The effects of weather conditions such as temperature and pressure on contamination flashover voltage of insulators were investigated theoretically, combining reported empirical relations. The flashover voltage theoretically calculated by the authors were compared with experimental data obtained in various parts of the world. Working curves were also presented for flashover voltage as a function of temperature and pressure for one contamination level and altitude     

Modeling current pulse shape and energy in surface discharges

Fast oscilloscope recordings of current pulse shapes of positive surface discharges have been analyzed. An equivalent circuit is proposed, and its parameters are derived from the oscillograms. Equivalent electrical circuits of electrostatic discharges provide a realistic way to simulate various discharges and to perform controlled laboratory tests. The equivalent circuit concept also gives an analytic expression of the discharge current, and thus, it is possible to calculate and estimate the charge transfer and the total discharge energy. These results are valuable for risk assessment of both the incendivity (i.e. dust and gas explosions) and the damage electrostatic discharges might cause to electronic devices     

Time-domain temperature variations of a composite insulator surface exposed to arc discharges

In this paper, a system of equations is presented, which describes time-dependant temperature variations for a dielectric surface exposed to an arc discharge. The formulas are derived for a circular (as well as any-shape) region interacting with the arc discharge. The final set of equations makes it possible to convert temperature values, measured at some depth beneath the sample surface which is exposed to the arc heating, to the corresponding surface temperature values. The theoretical results are verified by measurements according to the IEC 61621 test method, and numerical calculations are done for an epoxy composition that is used in composite insulator manufacturing.     

Surface discharges on polymeric insulator shed surfaces

This paper describes results of an experimental investigation into surface discharges occurring on the surface of polymeric insulators. Discharges on partially hydrophobic surfaces were found to occur across well defined dry bands, while discharges on hydrophobic surfaces appeared as small points of light occurring between discrete water drops. These discharges were observed to produce a localized loss of hydrophobicity. It is shown that these discharges are stable atmospheric-pressure glow discharges. The discharges are characterized by a high cathode voltage fall, dependent on the electrical conductivity of the water drop, and a voltage gradient in the positive column, dependent on the discharge current. A technique is presented for measuring the rate at which surface hydrophobicity of polymeric materials is lost due to the action of this type of discharge. It was found that the loss of hydrophobicity occurred predominantly in the region near the cathode     

覆冰绝缘子交直流闪络场路模型的研究

该文建立了覆冰绝缘子的交直流闪络场路模型,该模型将覆冰绝缘子的闪络分为空气间隙击穿前电弧的起始、空气间隙击穿后电弧在冰表面的发展和临界闪络判定3个阶段。通过对空气间隙击穿前后覆冰绝缘子电场分布的计算,并结合覆冰绝缘子闪络电路模型中电弧的E-I特性和U-I特性,求取覆冰绝缘子的临界闪络电压和电流,进而求取闪络过程中的U-I特性和I-t特性,并可以避免用电路模型采用简化公式计算覆冰各参量所产生的误差。通过与其他理论模型计算结果和真实覆冰绝缘子的试验结果的比较,对该文所建立模型进行了验证。     

Effect of residual stress on the surface flashover of aluminaceramics

The influence of surface residual stress on the surface flashover behavior of polycrystalline alumina in vacuum is investigated. The samples for the present investigation were prepared by using SiC and diamond abrasives of particle size ranging from 268 to 0.25 μm. Two types of polishing procedures, namely forward and reverse sequence polishing, are adopted in the present work. The surface residual stress of the specimens is determined by the two-exposure X-ray diffraction method. The flashover strength and the surface stress of the samples, subjected to forward sequence polishing (i.e., coarse to fine finish), are found to exhibit a random behavior with respect to the surface finish. Interestingly, a linear dependence between flashover strength and surface stress with respect to the surface finish is observed for the samples subjected to reverse sequence polishing (i.e., fine to coarse finish). The observed dependence between the residual stress and the flashover strength is discussed in terms of the high energy defect centers (e.g., deep traps) formed within the forbidden gap of the alumina insulator     

Preliminary study on icing and flashover characteristics of inverted T-type insulator strings

Electrical Engineering - Insulator icing flashover has always been one of the important factors influencing the safety of power grids in winter. Due to the limitation of tower structure and...     

罐式断路器瓷套沿面闪烙对保护动作的影响

运行发现LW13-363型SF6罐式断路器在断路器瓷套表面发生闪烙接地短路时,除了对电网一次系统造成冲击外,还会导致看似保护动作区外的继电保护装置误动作跳闸,直接扩大事故范围.通过调取误动保护装置的录波图和采样值进行分析,发现误动的保护装置其故障采样值确实在保护正方向动作范围内并非是装置原因.结合断路器放电位置和内部结构进一步分析研究,确认造成保护装置误动的原因是由于这种断路器自身结构所致.分析的结果使我们可以采取相对应的防范措施和对这种断路器结构进行改进,避免发生类似的问题.     

Electrical and thermal analysis of polymer insulator undercontaminated surface conditions

Electrical and thermal analysis of a 15 kV silicone rubber distribution insulator was made under contaminated surface conditions. The electric field on the insulator surface and in the surrounding area was determined by using the finite element method technique, while the temperature distribution along the insulator surface was calculated by solving the heat transfer differential equation numerically. A special mathematical treatment was used to reduce the heat transfer equation into a 1-dimensional problem. The effects of initial surface contamination upon the features of electric field was studied. The dependence of the change in insulator surface temperature as a result of leakage current flowing over the contaminated surface on the physical parameters involved in the heat conduction process was studied and is presented in detail     

XZP/XZWP4-160直流绝缘子覆冰闪络电弧特性的研究

在人工气候室内对覆冰XZP/XZWP4-160绝缘子的闪络特性及放电发展过程进行了试验研究。根据试验结果进行分析得出:弧根周围空气的热电离导致了电弧的发展,静电场力对电弧的发展起到了加速作用,电击穿仅发生在闪络最终的跳跃阶段;通过测量闪络过程中的放电电压、泄漏电流、闪络时间、覆冰水电导率、电弧长度及电弧半径等参数,得到电弧的发展速度及临界电弧长度均随覆冰水电导率的增加而减小,弧根电流密度随着气压的降低而增大;与正极性电弧相比,负极性电弧的发展速度快且弧根半径大。进一步分析覆冰绝缘子的闪络过程可知:覆冰绝缘子存在2个不同的闪络路径,即沿冰层外部和内部,这是由于电弧热作用蒸发的Na原子进入弧柱的方式不同造成的。