特高压GIS变电站中快速暂态过电压仿真及其特性分析

Simulation and Characteristics Analysis of Very Fast Transient Overvoltage in Gas Insulated Substation with Ultra High Voltage

在计算快速暂态过电压(VFTO)时,建立准确的全封闭气体绝缘变电站(GIS)暂态电路模型是影响VF-TO的关键。为此,将GIS内部暂态模型和GIS外壳传输特性模型相结合,建立了VFTO整体仿真模型。在GIS内部元件建模时,根据电弧的动态物理过程,建立隔离开关分段式动态电弧模型;结合交变电场下电介质极化原理,建立金属氧化物避雷器(MOA)暂态电路模型;并从GIS本体结构出发,通过三维电场分析,获得较准确的GIS元件暂态模型及参数;结合传输线理论和相模变换,获得GIS外壳暂态模型,并建立了考虑接地体间互感作用的暂态地网模型。最后结合国内某1 100kV气体绝缘变电站,进行VFTO详细仿真。仿真结果表明,分段式动态电弧模型下VFTO幅值标幺值高达1.270(基准值取898kV),较指数时变电弧模型下的VFTO幅值标幺值增加了17.59%,当考虑了MOA的非线性特性时,VFTO的振荡幅值有不断减小的趋势,在仿真时间将近20μs时,VFTO标幺值振荡幅度至0.8。最后将仿真结果与实测波形进行对比分析,VFTO幅值标幺值相差0.2～0.4,证明了所建立的VFTO仿真整体模型的实用性。

In the computer simulation process of very fast transient overvoltage （VFTO）, establishing an accurate model of gas insulated substation（GIS）component is a key factor that affects the accuracy of VFTO. Thus, a VFTO overall simulation model was established combining the inner transient model and the model of transmission characteristics of GIS enclosures. Moreover, A dynamic arcing model was proposed based on the arc physical process, and a metal oxide surge arrester（MOA） transient circuit model was established based on the polarization theory in alternating electric field. By 3D electric field analysis, an accurate GIS equipment equivalent model and its parameters were obtained based on the body structure of the GIS. Furthermore, according to the transmission lines theory and the phase-model transformation method, the GIS enclosure was modeled, and a transient ground model was established by taking the mutual induction within the grounding body into consideration. Finally, taking a 1 100 kV GIS as example, we simulated the VFTOs in detail. The results show that the per unit amplitude of the VFTO in the segmented dynamic arc model is up to 1. 270 { taking the corresponding value as a reference）, increased by 17. 59% over that of the index variable arc model. After taking the nonlinear characteristics of the MOA into consideration, the oscillation of the VFTO amplitude decreases persistently, and is reduced by 20% when the simulation time is close to 20. According to the comparison between the simulation results and the measured waveform analysis, the difference of per unit VFTO amplitude is in a range of 0.2~0.4, indicating the presented overall VFTO simulation model is valid.