Ursachen leitungsgebundener Störungen eines KFZ-Inverters im CISPR 25-Komponententest

This article presents results from an investigation on conducted emissions of an automotive inverter in a CISPR 25 component level test setup. The primary goal of the investigation is to understand the main effects influencing the shape of the disturbance voltage’s frequency spectrum at the line impedance stabilization network.     

电力变压器微水在线测量的先进方法

研究了测量变压器油-纸绝缘的电力变压器中水含最的新方法.微水的扩散和平衡是和潜在的水分有关.比较了测量变压器内纸绝缘中水含量的各种方法.微水平衡图的常规应用会导致错误的结果,因此,创建了改成以微水吸收量和相关材料老化参数的微水平衡图.使用变压器油中的相对湿度来绘制微水平衡图先进的表示法,产生了比较好的效果.此外,按变压器油和绝缘材料中的活跃的水分来确定湿度,能提供方便、精确和连续的测量,并且直接反映变压器油-纸绝缘中的水分的破坏性潜力.这些均可在在线系统中显示出来.     

采用UHF测量方法对电力变压器进行现场局部放电探测和定位

对高电压电力变压器的绝缘情况作出可靠的判断是安全和节省成本运行的基本条件.介绍一种重要的现场有条件测定方法(局部放电测量).为了将UHF PD信号从电力变压器的油箱内分离出去,可将敏感的UHF传感器应用在放油阀上.通过对带电磁UHF的电力变压器的局部放电和声学方法的比较调查发现:与声信号比较,对UHF信号具有更低的衰减作用.文中给出的若干现场/在线测量以及实验室实验显示非传统的局部放电测量方法对于现场出现的噪声具有优越性和抗扰性.     

The influence of surface charge on lightning impulse breakdown ofspacers in SF6

We have investigated the influence of surface charges on the discharge development across particle contaminated spacer surfaces under SF₆ for lightning impulse (LI) voltages (1.2/50 μs). Surface charges may be generated by dc, ac or lightning impulse stress. The discharge characteristic shows a strong reduction of the insulation strength if the applied voltage and the surface charge have opposite polarities. The investigations were performed with a needle protrusion attached to the bottom electrode to give severe field distortion. The bottom electrode was biased positively. The influence on the discharge process is observed by measuring the surface charge distribution and predischarge currents. The results reveal changes in streamer onset voltage, streamer to leader transition, and leader development