GIS中电磁波传播特性的仿真研究

Simulation Analysis on the Propagation Characteristics of Electromagnetic Wave in GIS

为研究UHF信号在GIS中的传播特性,采用时域有限差分法进行了仿真建模和计算。GIS内部的局部放电会在腔体中激励超高频(UHF)电磁波信号,UHF法是通过对局部放电时产生的超高频电磁波信号进行检测,获得局部放电信号的有关信息以实现对设备的绝缘状态诊断和评估。UHF法抗干扰能力较强、灵敏度高。仿真结果表明,UHF信号在GIS内传播时呈现明显的时延特性,有利于局放源的定位;UHF信号的强弱和检测点与局放源的夹角Φ有关,Φ=0°和180°时信号的能量最大;局放脉冲越陡,在GIS腔体中激励的高次模波分量越大。

Ultra-high frequency （UHF） electromagnetic wave can be radiated by partial discharge （PD） in gas insulated switchgear （GIS）. UHF method is used for evaluating the insulation condition of GIS by analyzing the partial discharge signals information which is detected by UHF sensors. As the most of noises are under 300MHz, UHF method can avoid the noises, particularly the corona noise in the air, and effectively detect the partial discharge signal in GIS. The experiences of detecting partial discharge signals which were carried out by the UHF measuring system show that UHF method has good sensitivity for detecting partial discharge. In order to explore the relationship between partial discharge sources and radiated ultra-high electromagnetic wave signals, the propagation characteristics of ultra-high frequency electromagnetic wave in GIS are analyzed. The model for detecting PD signals in GIS is built and simulated by using the finite difference-time domain （FDTD）. By changing the parameters of PD sources and probe, the propagation characteristics of ultra-high frequency electromagnetic wave in GIS were calculated by simulation. The simulation results shows that there is a time-delay effect in electromagnetic wave propagation in GIS, and this will be benefit for locating position of PD source; the detecting signal is related to the angle between detecting position and PD source site, and the energy received is the largest, and the sharper the PD signal is, the more high-modes are excited.