高电压纳秒气体开关绝缘恢复特性的实验研究

气体开关绝缘恢复曲线中存在的"平台现象",大大延长了开关的绝缘恢复时间,但其存在原因尚未取得共识。为此,结合GW级Tesla型ns脉冲源,在开关工作电压约220 k V情况下,研究了不同气压(0.1~7 MPa)的N2、H2、SF6 3种气体开关的恢复特性及稳定性。结果表明:对于N2、H2开关,随着气压的升高,开关恢复曲线中的"平台现象"逐渐减弱,当气压超过一定阈值后,开关"平台现象"消失;对于SF6开关,则不存在"平台现象"。可见对于N2、H2、SF6 3种气体"平台现象"产生的原因是不同的,同时Tesla型脉冲源对开关的"平台现象"也具有一定的影响。N2、H2、SF6气体绝缘恢复系数达到95%的最短时间分别为7.1 ms、0.68 ms、5.4 ms。     

氮气短间隙的耐受电压和气体密度恢复特性

为了提高气体火花开关重复运行频率,对氮气短间隙的耐受电压和气体恢复特性进行了研究。采用＂双脉冲法＂获得了气隙耐受电压恢复特性,利用Mach-Zahnder干涉仪记录了气体密度的恢复过程,用CCD相机拍摄了放电图像。实验发现：耐受电压恢复过程分为静态击穿电压恢复和过电压击穿能力恢复两个阶段,后者所需的时间远超过前者。即使气体密度完全恢复了,气隙也仅恢复其静态击穿电压,其原因可能是放电残留的长寿命氮原子在阴极上复合导致阴极电子发射,持续不断地为放电提供初始电子。＂双脉冲法＂实验中气隙两次击穿的路径通常是分离的,说明气体绝缘最薄弱之处并不一定位于第1次火花放电通道上。     

气体火花间隙开关的自击穿性能研究

为了解气体火花间隙开关的自击穿性能,文中从自击穿实验角度着手,对电场不均匀度进行了仿真计算,测量了两电极气体火花间隙开关不同间隙距离下的自击穿电压,通过计算相对极差和变异系数来分析自击穿电压的稳定性并进行韦布尔检验。实验结果表明,自击穿电压随间隙距离的增大而增大并近似线性关系;间隙距离是影响自击穿电压稳定性的重要因素,自击穿电压的稳定性随间隙距离的增大而增大。从自击穿稳定性角度来看,可以适当增大气体火花间隙开关的电极之间间隙距离来增强自击穿电压稳定性。     

绝缘护套对间隙交流击穿特性的影响研究

在架空输电线路上包覆绝缘护套是工程中常用的防鸟害措施之一,鸟粪与护套表面之间空气间隙的击穿电压直接影响护套的配置方案.本文采用铜棒模拟鸟粪,通过试验研究了不同空气间隙距离下,击穿电压随护套厚度的变化特性以及护套缺陷对击穿电压的影响.结果表明:与不包覆护套的裸导线相比,包覆厚度为2.0、3.0、3.5 mm护套的导线,间隙击穿电压可分别提高17.7％、33.1％、41.6％;与相同厚度的全新护套相比,存在击穿点且厚度为2.0、3.0、3.5 mm的护套,间隙击穿电压分别降低了70.6％、62.8％、44.2％,说明有击穿点的护套厚度越小,击穿电压降低幅度越大.     

气体绝缘开关装置中快速暂态过电压的抑制

SF6气体绝缘开关装置中隔离开关操作会产生快速暂态过电压(VFTO)，危害电力设备的安全运行。章分析了影响快速暂态过电压的因素，并且比较了两种抑制快速暂态过电压方法的效果。     

预电离开关触发间隙击穿时延特性

为了研究预电离开关触发间隙在是否叠加主间隙电场时的击穿时延特性,采用基于气体放电流体模型和有限容积法的二维程序对氮气中气压0.1～0.7MPa、电极间距0.5mm和1mm、间隙上脉冲电压上升速率与气压的比值d(u/p)/dt等于0.8 kV/(ns·MPa)和0.4 kV/(ns·MPa)、主间隙与触发间隙之间分压比不同时叠加主间隙径向电场下触发间隙的击穿过程进行模拟并对比实验数据。结果表明,由于d(u/p)/dt影响间隙中的平均归一化电场Eav/p的变化过程,d(Eav/p)/dt值确定时,气压、初始电子产生的时刻和电极间距等是影响间隙击穿时延的主要因素。叠加主间隙径向电场会增强触发间隙中的空间电场并加快电子崩的发展过程,但也会使电子沿径向漂移,导致击穿时延增长。为削弱叠加径向电场的影响,可以减小分压比、增大d(u/p)/dt和阳极直径。     

不同气压和电极间距对开关绝缘恢复的影响

为缩短脉冲加速器多脉冲运行时脉冲间隔以及提高重频运行时重复频率,利用多脉冲调制器研究了气体开关的重复频率特性以及在相同电极间距、不同气压下(0.5、1、1.5、2MPa)氮气气体开关的绝缘恢复特性。实验表明,随着气体压强的增加,气体的绝缘恢复时间变长,击穿电压恢复>90%的间隔时间,从50ms增加到78ms;开关间距的改变对绝缘恢复时间影响有限,不同间距(7.3,27.4mm)下其击穿电压恢复>90%时间约为50ms。最后针对相关文献给出的结果,对压强、电极间距对绝缘恢复的影响进行了分析讨论。     

一种多间隙气体开关击穿特性的实验研究

快前沿直线型变压器驱动源(FLTD)是一种可以直接获得100 ns脉宽的脉冲功率源新技术,在Z箍缩、闪光照相、强激光和高功率微波方面具有重要应用。为了寻求用于FLTD的多间隙气体开关的合适结构,设计了一种场畸变多间隙气体开关。该开关含有6个间隙,各个间隙距离相等,开关间隙总长度为30 mm。开关中间电极为锚式固定结构,每个电极由3只螺钉固定在绝缘筒壁内侧,数值计算了开关的电场分布,实验研究了开关的自击穿及触发特性。结果表明,开关自击穿特性曲线与经验公式曲线基本符合,自击穿电压的分散性<3.2%;在工作系数为50%时,开关仍能正常触发,触发时延约百ns;在工作系数为60%时,触发脉冲为150 kV/15 ns的情况下,开关触发时延约60 ns,抖动时间约5 ns。     

电力变压器油纸绝缘系统气隙特征分析

针对电力变压器油纸绝缘系统由于自身老化产气、换油处理不当等引入气隙(空穴)的影响绝缘性能研究方法的不足,引入回复电压法有效诊断油纸绝缘状态来判断气隙状况。在理解介质响应理论基础上,建立了油纸绝缘模拟实验,统计分析并拟合了测量数据,研究了不同充电时间下绝缘系统中气隙含量的变化对回复电压特征参数的影响规律。结果表明:回复电压最大值随绝缘系统中气隙含量的增加呈二次线性规律增大,而中心时间常数随绝缘系统中气隙含量的增加呈二次线性规律减小,初始斜率随着绝缘系统中气隙含量增加呈三次线性规律增大,最后对多台实际变压器进行测试分析,验证了回复电压法可对油纸绝缘系统中气泡情况有效诊断的结论。     

Dielectric characteristics of turn-to-turn insulation models of gas-insulated transformer under very fast transient voltages

This paper deals with the partial discharge inception voltage (PDIV) and breakdown voltage (BDV) characteristics of turn-to-turn insulation models for SF₆ gas-insulated transformers in the presence of steep-front short-pulse voltages, whose waveforms are 35/65 ns and 50/370 ns. It was determined that PDIV at nanosecond pulses were 1.05 to 1.15 times higher than those at standard impulse voltages and that the BDV at nanosecond pulses were about 1.4 times higher than those at standard impulse voltages. The ratio of impulse PDIV to ac PDIV is 1.40 to 1.48 for standard impulse voltages and 1.32 to 1.37 for switching impulses. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 36–43, 1997     

V-t characteristics of SF6 gas during lightning surges

The waveform of a standard lightning impulse differs greatly from those of actual lightning surges acting on GIS. This raises the problem of the equivalence of the standard lightning impulse. This report describes the effect of voltage waveforms on insulating performance in an SF₆ gas gap subjected to fast oscillating impulse voltages simulating actual lightning surges, and the evaluation of V-t characteristics by applying the equal area criterion. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(4): 1–11, 1997     

Impulse insulation characteristics of a composite insulation system having a wedge gap in SF6 gas

Impulse insulation characteristics were investigated in a composite insulation system having a wedge gap in SF₆ gas. The partial discharge inception voltages of wedge gaps with various types of film were measured and compared with the calculated breakdown voltages estimated from Paschen's curve of SF₆ gas. Also discussed is how the charge accumulated on the film surface due to a partial discharge had an effect on the creepage breakdown voltage. Partial discharge inception voltages in wedge gaps were higher with higher SF₆ gas pressures and with lower film permittivities. Creepage breakdown voltages depended little on gas pressures or on creepage distances. The dependency of breakdown voltages on gas pressures and the effect of polarity on the breakdown voltage differed with the types of film. This may be partly because the charge on the film due to partial discharge had an effect on the discharge propagation, and that charging of the film differed with the types of film.     

Insulation characteristics of SF6 gas for nonstandard impulse voltage polarity reversal pulse waveforms

Evaluation of insulation strength for lightning surge that actually enters into substations is important in estimating insulation reliability of gas‐insulated equipment. The standard lightning impulse voltage (1.2/50 µs) is used for factory tests. However, the actual lightning surge waveforms in substations are complex and are usually superimposed with various oscillations. Insulation characteristics of SF₆ gas as a function of such complex voltages have not been sufficiently clarified. This paper deals with gap breakdown characteristics in SF₆ gas under submicrosecond pulses. Breakdown voltages are lower under a polarity reversal condition than under a monopolarity condition. The cause of this difference is discussed while observing discharge propagation using an image converter camera. The electrode size effect is also discussed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 146(4): 18–25, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10246     

基于TCAD的脉冲作用下晶闸管反向恢复特性仿真研究

研究暂态脉冲电压作用下高压晶闸管反向恢复特性对于换流阀参数设计、故障保护以及试验检测等方面具有重要意义。本文首先参照晶闸管实际结构,建立了晶闸管二维半导体仿真模型,基于载流子漂移扩散模型求解,仿真获得了晶闸管静态击穿特性和反向恢复电流特性,通过与实验结果进行对比,验证了仿真模型的有效性。在上述基础上,建立了半导体器件-电路仿真混合模型,仿真表明：反向恢复期间电压脉冲易导致晶闸管误触发,误触发电压随脉冲施加时刻后移而升高,并对比分析了正常导通和误触发导通时晶闸管内部电流密度变化的异同。     

Breakdown characteristics of oil and paper insulation for a very fast transient voltage

This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043     

关于快速脉冲充电技术的研究

直流恒压恒流蓄电池充电设备容易造成电池过充或充电不足,且充电时间较长。本文简述了快速脉冲充电技术的理论基础,并根据需要设计了一套能有效防止过充和欠充的充电系统。     

基于交流电流法评估大型电动机环氧云母绝缘老化特征的研究

对大型电动机环氧云母绝缘线棒进行了多因子加速老化试验,在不同老化阶段进行了交流电流、击穿电压测量。根据交流电流曲线的特点,提出了求取第二电流急增点电压的新方法－－逐点拟合法,并分析了第二电流急增点电压与剩余击穿电压的相关性。结果表明：逐点拟合法能准确地求取第二电流急增点电压,且用此电压值推算环氧云母主绝缘的剩余击穿电压是有效的。