基于电荷累积的棒-板间隙流注放电过程仿真

Fractal Dynamic Streamer Discharge Simulation of Rod-plane Air Gap Based on Charge Accumulation

棒-板间隙放电过程的建模与仿真对于长空气间隙放电机理研究及特高压输电工程的外绝缘设计具有重要意义。为此建立了棒-板间隙动态流注分形发展模型,在已有的分形流注模型的基础上,提出了基于动态边界修正的电场计算方法以及基于电荷累积的时间参数求取方法。通过对间隙空间进行网格剖分,求解电场分布方程与电荷累积方程,得出间隙电场变化以及流注步进式发展的时间及动态电荷累积。本模型针对流注起始、流注发展、放电结束和电荷累积等过程进行了建模,并运用模型对于不同电压幅值(230 k V、590 k V)1 m棒-板间隙雷电冲击(2.0/50μs)流注放电过程进行了仿真,并和试验结果进行了对比分析。结果表明,雷电冲击电压为230 k V时,流注发展长度约为20 cm,流注发展时间为5.02μs,流注发展平均速度为3.98×104 m/s,流注通道电荷累积总量达到23.2μC;雷电冲击电压为590 k V时,1 m棒-板间隙被击穿,流注发展时间为9.92μs,流注发展平均速度为1.01×105 m/s,击穿前其速度达到1.60×105 m/s,整个击穿过程流注电荷累积总量为258.3μC。新的模型在放电通道长度变化,放电过程电场波形,流注发展过程电荷粒子的累积等方面均与试验结果基本一致,具有一定合理性。

The simulation of rod-plane air gap discharge process is of great significance to the research of long air gap discharge mechanism and the design of UHV transmission projects. We built a discharge model of positive fractal dy- namic streamer of rod-plane air gap. On the basis of the original fractal streamer model, we proposed an electric field calculation method based on the dynamic boundary condition, and a new calculation method of the time parameters based on the charge accumulation process. In the model, the electric field and development time of discharge step were obtained by solving the electric field distribution equations and charge accumulation equations. The processes of streamer starting, streamer development, charge accumulation, discharge extinguish were all contained in the model. Discharge process of various voltage amplitudes （230 kV,600 kV） and the waves of lightning impulse（2.0/50 μs） were simulated by this model in the lm rod-plane air gap.The results show that,for the gap of 230 kV, the length of streamer is 20 cm, streamer time is 5.02μs, velocity is 3.98× 10am/s, and charge accumulation is 23.2 μC; while for the 600 kV, the gap is discharged, streamer time is 9.92 μs, velocity is 1.01 × 104 m/s, and it raises to 1.60× 105 m/s before discharge, and charge accumula- tion is 258.3 μC. The model matches the test results well in the dynamic processes of the length of discharge channels, electric field, and charges.