反向恢复期脉冲作用下高压晶闸管失效分析

本文搭建了高压晶闸管反向恢复期脉冲作用实验平台与特性参数测试平台,研究了高压晶闸管在反向恢复期不同阶段遭受脉冲冲击过程中的特性参数变化规律,并对退化和失效晶闸管拆片分析,结果表明：反向恢复期脉冲作用下高压晶闸管退化或失效表现为阻断能力的退化或丧失,由此引起晶闸管漏电流剧增,漏电流可作为表征晶闸管状态变化的特征参量;反向恢复期初期和中期冲击失效器件芯片上可见明显击穿点;反向恢复期中期冲击阻断能力退化芯片上可见热应力作用形成的圆斑;反向恢复期末期冲击失效器件可在芯片边缘与绝缘橡胶相接处见雪崩击穿闪痕。#$NL关键词：高压晶闸管; 电压脉冲; 反向恢复期; 失效分析#$NL中图分类号：TM461.4     

Imaging breakdown spots in SiO/sub 2/ films and MOS devices with a conductive atomic force microscope

Conductive atomic force microscopy (C-AFM) was used to study the dielectric breakdown of SiO/sub 2/ layers at a nanometric scale. First, bare oxide regions were stressed and broken down using the tip as the metal electrode of a MOS structure. The results show that the initial breakdown is electrically propagated to neighbor regions, affecting their dielectric strength. Moreover, the area affected by the initial breakdown depends on the breakdown hardness. In particular, it is shown that this area is smaller when the current through the structure is limited during the experiments. The effect of the current limitation is analyzed in detail. Based on the results, a qualitative picture of the breakdown process is presented, which accounts for this effect. Finally, for the first time, the breakdown spots in standard MOS devices (with poly-Si gate) are electrically imaged with C-AFM. The areas of the observed spots are in agreement with those obtained on bare oxides.     

Breakdown conditioning characteristics of long gap electrodes in a vacuum

An improvement in dielectric strength is required in vacuum circuit breakers (VCBs) intended for use in higher voltage systems. In order to develop higher voltage VCBs, it is important to improve the dielectric strength in a vacuum based on consideration of the vacuum breakdown mechanism. Particularly for gaps longer than 10 mm, little is known about the breakdown mechanisms and their quantitative analyses in a vacuum. This paper discusses the breakdown conditioning characteristics of long gap electrodes, under a non-uniform electric field in a vacuum. We treat gap lengths of up to 50 mm in this paper. The conditioning characteristics are investigated under impulse voltage applications. A negative standard lightning impulse voltage was applied to rod-plane electrodes made of Cu-Cr and SUS304 for different tip radii and gap distances until the conditioning effect was completed. We observed illumination spots on electrodes at each breakdown during the conditioning process and calculated the corresponding breakdown field strengths. Experimental results revealed that the tendency of breakdowns associated with long gaps is different from that for the short gaps. As a result, we clarified that the breakdown field strengths are nearly constant at 110-120 kV/mm at the distances longer than 10 mm, and the breakdown field strength is at its maximum when the gap distance is about 5 mm.     

Electron avalanches. II. Fractal morphology of partial microdischarge spots on dielectric barriers

For pt.I see ibid., vol.10, no.4, p. 689-699 (2003). Microdischarge spots appearing on surfaces of dielectric barriers in sandwiched electrode systems have been studied. The study has been focused on streamer microdischarges which are a subject of continual interest not only in plasma physics (dielectric barrier discharges) but also in HV technology (partial discharges). The microdischarge spots have been visualized using photographic films that have played the role of dielectric barriers in experiments. The digitized pictures of microdischarge spots have been subjected to multifractal analysis. An inner structure of spots has been revealed and ascribed to streamer heads. The monofractal nature of the overall sets of microdischarge spots as well as the monofractality of the borders of the dark spot centers has been indicated. The inner structure of the dark centers has been classified as a non-fractal planar object. The study represents a first attempt to analyze microdischarge spots on dielectric barriers using general multifractal formalism.     

Initial images of complete breakdown of liquid nitrogen/polymerfilm

This paper describes an experimental study,on the prebreakdown phenomena in a liquid-nitrogen/polymer-film composite subjected to dc ramp and step voltages under point-plane electrode system. In order to clarify the formative process of the complete breakdown of the composite, photographic observation was carried out using a long image guide scope and an image intensifier with high speed gate in the nanosecond region. When a negative-plane electrode was covered by a polymer film (N-cover arrangement), a luminous region on the initial image of the complete breakdown was located near the negative-plane under both the ramp and the step voltages. These results suggested that the complete breakdown of the composite in the N-cover arrangement was caused by the film breakdown due to positive charges deposition and subsequent electron emission from the film breakdown spot. When a positive-plane electrode was covered by the film (P-cover arrangement), film breakdown could not trigger the complete breakdown under the ramp voltage because the film breakdown occurred at a low applied voltage. However, intense light near the positive-plane was observed at the initial stage of the complete breakdown under the relatively high step voltage. This was because the film breakdown under the high applied voltage induced the positive streamer propagation from the film breakdown spot     

用于荧光灯管的全新第四代电子源（二）

在荧光灯（FL）管中,人们凭借经验发现了一种全新的电子源,它是高温氩晕空间（HTACS）。HTACS在带有微小BaO颗粒钨丝线圈的受热裸金属斑点上形成,在氩气体空间中,取自处于负电势阴极电极上HTACS的电子,向处于正电势阳极电极上的HTACS运动。在点亮FL管中,来自HTACS的流光电子在所运行ac电压处于正电势期间...     

激光诱导击穿光谱技术应用于煤质分析的研究综述

实时掌握入炉煤的煤种特性,有利于燃煤发电机组的安全经济运行,但由于煤质在线分析技术的缺乏,一定程度地制约了火力发电燃烧优化技术的实质性发展,激光诱导击穿光谱(laser-induced breakdown spectros-copy,LIBS)技术作为一项潜在的在线分析技术被引入煤质在线分析领域。为此,分别从基础实验研究、定量分析方法研究和工业应用研究3个方面综述了国内外关于LIBS技术在煤质分析方面的研究现状,探讨了其中需要解决的关键问题。在LIBS技术现有发展的基础上,需要重点解决LIBS检测煤质所需的定量分析模型的精确度和煤种适应性、分析装置良好的现场适应性和长期运行的可靠性等问题。     

Space charge formation and breakdown in polyethylene influenced by the interface with semiconducting electrodes

This paper deals with the influence of interface between polyethylene and semiconducting electrode on the space charge formation and electrical breakdown. Low‐density polyethylene (LDPE) films attached with different semiconducting electrodes were subjected to the DC breakdown test, and corresponding space charge distribution was measured. A heat treatment to LDPE itself did not bring about a significant change in space charge profile; however, when a semiconducting electrode was hot‐pressed, the impurities would migrate into LDPE at high temperature, leading to the change in space charge profile. Furthermore, it was suggested from the comparison between the results with degassed and as‐received semiconducting electrodes that some carriers relating to impurities in the electrode would move into LDPE under the voltage. In addition, it was shown that the breakdown is not determined by the field at the cathode which can supply sufficient electrons, but by the maximum field across the specimen, suggesting that an increase in conduction current due to the generation and/or injection, rather than the electronic avalanche process, leads to the breakdown. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 19–25, 2002     

电力电缆线性高阻击穿故障的特点及定位方法

交联聚乙烯和聚氯乙烯绝缘电力电缆的大量应用中,出现了一种新型的高阻击穿:其等效电阻相当稳定,用兆欧表500 V至5000 V档测量,击穿点绝缘电阻几乎不变,该类击穿点也许不能承担高电压,但很难降低其电阻,即使施加高压脉冲也无法击穿,因此难以通过脉冲电流法,乃至二次脉冲法、三次脉冲法定位。该类高阻击穿故障被定义为线性高阻击穿故障,是目前公认的定位难点。本文详细讨论其形成的原因,定位方法等。结论是:线性高阻击穿可以使用高压定位电桥直接定位;或通过合适的烧穿源降低绝缘电阻,再使用电桥或波反射法定位,关键是烧穿源必须有足够高的电压及功率。     

10kV电力电缆故障检测

本文介绍了10kV电力电缆故障产生的主要原因及故障类型,给出了电力电缆故障点查找的基本流程,同时对目前常用的故障粗测和精确定位方法进行了阐述。结合一起10kV电缆故障查找案例,对故障检测全过程进行了梳理与分析。最后,介绍了目前电缆故障检测新技术的应用。     

含光伏的主动配电网非对称故障条件下对并网点电压影响的研究

对于地区二次变电站其中性点一般不直接接地,随着高密度分布式电源的接入,若输电线路发生接地故障,会导致该变压器中性点电压升高,甚至会击穿,进一步影响并网点电压。文中针对含光伏的主动配电网,分析了主变中性点击穿前后、线路保护动作前后,影响并网点电压的主要因素,并画出含光伏的主动配电网的各序网络图,推导光伏电源并网点电压理论计算公式,同时,文章通过PSCAD仿真验证了公式的正确性,比较了主变中性点击穿前后,分布式电源并网点电压变化规律。     

基于光电检测技术的玻璃间距测量方法的研究

本文主要研究基于光电检测技术的透明玻璃间距测量方法和实验装置。本测量系统由激光光源、光学系统、图像采集系统及光点位置估算系统组成。本文主要讨论了采用重心估算（CCP）傅立叶相位偏转法（FPS）计算光点的位置。此外,为了验证上述理论的可行性,本研究利用计算机软件模拟并讨论了噪声信号对上述2种光电估算法的影响。数值仿真结果显示信号中的直流分量和背景噪声对CCM方法的仿真精度的影响要比FPS大;当光斑分别为艾里图样和高斯图样时,CCM方法和FPS方法的计算精度基本相同。     

高压并联电容器箱壳爆裂及其对策

分析了高压并联电容器在运行中发生箱壳爆裂的起因和必要条件,认为只有当具备电容器的内部发生贯穿性击穿、电容器接入处系统有足够大的短路容量或并联电容器容量足够大及故障电容器的端子与系统或与并联的完好电容器间具有1条低阻抗放电通道这3个条件时才会发生箱壳爆裂,提出了为防止高压并联电容器在运行中发生箱壳爆裂事故所应采取的对策和...     

高压并联电容器箱壳爆裂及其对策

分析了高压并联电容器在运行中发生箱壳爆裂的起因和必要条件,认为只有当具备电容器的内部发生贯穿性击穿、电容器接入处系统有足够大的短路容量或并联电容器容量足够大及故障电容器的端子与系统或与并联的完好电容器间具有1条低阻抗放电通道这3个条件时才会发生箱壳爆裂,提出了为防止高压并联电容器在运行中发生箱壳爆裂事故所应采取的对策和措施。     

Vacuum electrical breakdown characteristics and surface condition of Ti electrodes with oxidation conditions

Outgassing from an electrode surface is regarded as a major factor leading to electrical breakdowns in vacuum. Recently oxidation treatment at 200/spl deg/C was reported as an effective means of reducing Ti outgassing. In this paper, we report our measurement and comparison of the electrical breakdown characteristics of Ti electrodes with different oxidation conditions (without oxidation, oxidation at 200/spl deg/C, oxidation at 450/spl deg/C). In addition, we analyzed electrode surfaces before and after breakdown experiments in situ with X-ray photoelectron spectroscopy (XPS). Before oxidation, we machined the electrode's surfaces to the roughness of 0.8 /spl mu/m Rmax with diamond turning. Breakdown experiments demonstrated that the breakdown field is highest at the first application of voltage to electrodes with oxidized at 200/spl deg/C. Before breakdown experiment, surface analysis revealed that all the sample electrodes had a large amount of carbon originating from the hydrocarbons of contaminants, and after the experiments, they revealed that the carbons had disappeared. To obtain breakdown characteristics of electrodes with smoother surfaces, we conducted experiments on electrodes with a surface roughness of 0.05 /spl mu/m Ra. For these electrodes, the breakdown field was higher at first breakdown; the repetitions required to achieve saturated breakdown fields were significantly fewer, and the amount of carbon on electrode surfaces before breakdown was less.     

运用冲闪法检测电力电缆故障

结合实例对运用冲闪法测距进行了分析,并提出了使故障点充分放电应采取的措施,以及测试时应注 意的问题及解决措施。     

铜屏蔽层绕制方式对绝缘管母安全运行影响的研究

为了研究铜屏蔽层绕制方式对绝缘管母运行安全的影响,针对某地区110k V变电站35k V侧绝缘管母出现的外护套烧蚀击穿故障案例进行了研究。通过管母烧蚀击穿点的红外热成像,结合管母的有限元仿真对管母铜屏蔽层在绕包和叠包绕制方式下管母半导电层的电势分布、电流密度以及阻性损耗密度进行了对比分析。研究结果表明:两种绕制方式下管母的半导电层电势分布、电流密度及阻性损耗存在明显差异。管母采用绕包时在铜屏蔽层截断处容易形成局部高电势,半导电层表面电流及局部阻性发热功率密度大,半导电层发热严重并存在明显的过热点;采用叠包时管母半导电层的表面电势、电流密度及局部阻性发热功率接近于零,未发现明显的局部过热点。这些特征可为改进管母铜屏蔽层的绕制方式和指导实际生产工作提供理论依据。     

纵磁场中真空扩散型电弧阴极斑点的分裂和运动

在作者的实验条件下观察发现:真空扩散型的阴极班点开始分裂的临界电流随纵磁场的增大而减小;而且阴极斑点群在纵磁场的影响下动态地接近均匀分布于阴极表面一定的面积内,并在正弦半波电流峰值附近达到最大,而稍滞后于电流峰值;斑点群膨胀和收缩的速率呈现“双驼峰”特性。     

A study on hot spot detection possibility in simulated oil‐filled‐type transformer tank by using ultrasonic methods

Failure of oil‐filled‐type (OFT) power transformers usually results in very big losses comprising the loss of the transformer itself as well as production loss in industry. Most of the energy lost in OFT transformers, induced by faults, will become heat at a location close to the fault, which then becomes a hot spot. The detection of hot spots in OFT transformers can be an effective way for transformer fault location and diagnosis. As the OFT transformer enclosure is completely sealed and is opaque, to date there is no effective way to find out hot spots in them. It is known that ultrasonic energy can be transmitted into the sealed transformer enclosure which is filled with the fluid, and ultrasonic waves can be affected by the temperature of the materials they propagate through; so the ultrasonic method can be a possible method for hot spot detection. In this paper, we describe a study on the possibility of developing a method to detect hot spots in an environment filled with a fluid, simulating a transformer. Trails using a different times‐of‐flight (TOFs) evaluation techniques and attenuation measurement of the ultrasonic energy propagated were carried out, which showed encouraging results for locating the hot spot as well as measuring the hot spot temperature in fluids; we also discuss the possibility of applying these results to the diagnosis of OFT transformers eventually. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

光伏组件热斑对发电性能的影响

针对光伏电池上的热斑问题,分析了热斑生成的原因和对发电性能的影响,介绍了红外热像仪检测热斑的方法,并探讨了用旁路二极管解决热斑危害的可能性,以提高光伏电池组件的寿命。