高压直流下g3气体中气固界面电荷积聚特性及其对沿面闪络的诱导机理

In DC GIL, the microscopic mechanism of the surface flashover caused by the charge accumulation at the gas-solid interface is complicated and is difficult to study quantitatively, which is the bottleneck that restricts its development. It is also a significant challenge for the application of new eco-friendly gases in DC GIL. Aiming at the widely concerned g3 gas, this project will use high-precision surface charge measurement technique and inversion algorithm, as well as charge accumulation kinetic model, to investigate the spatial-temporal evolution of the charge accumulation at the gas-solid interface under DC voltage, mainly focusing on the different patterns of charge accumulation and the mechanism of their formation. Then, the surface flashover characteristics in g3 gas will be studied. Special attentions are paid to the application of advanced optical plasma diagnostic methods to analyze the transient and microscopic parameters and processes in the surface flashover discharge. Much attention will be paid to the mechanism of the influence of surface charges on the processes of streamer corona initiation and streamer-to-leader transition, which is the core issue of this project. From the perspective of field distortion effect and seed charge effect, the mechanism of surface charge-induced flashover will be revealed. Finally, the influence of charge transport characteristics within the dielectric surface on the flashover discharge will be studied and the guidance and feasible method for the surface insulation optimization will be provided. This research will help to enrich and develop the surface discharge theory, and provide supports and references for the development of the next generation eco-friendly DC GIL.

直流GIL中由于气固界面电荷积聚导致的沿面闪络问题，微观物理机制复杂、定量研究难度较大，是制约其发展的瓶颈，也是新型环保混合气体在应用时面临的重要挑战。本项目针对目前广受关注的g3气体，采用高精度表面电荷测量技术和反演算法，结合气固界面电荷积聚动力学模型，研究直流电压下气固界面电荷积聚的时空演化规律，重点分析电荷积聚的不同模式及其形成机理；进而研究g3气体的沿面放电特性，特别注重应用高时空分辨的等离子体光学诊断手段来定量分析沿面放电中的微观、瞬态参数和物理过程，瞄准气固界面电荷对流注电晕起始和流注-先导转化过程的影响机制这一核心问题，从场畸变效应和种子电荷效应两个角度，深入揭示气固界面电荷对沿面闪络的诱导机理；掌握介质表层电荷输运特性对沿面放电的影响规律和机制，为气固界面绝缘优化提供指导。本研究有助于丰富和发展气体沿面放电理论，为下一代环保型直流GIL的研发提供重要理论基础和科学依据。

直流GIL中由于气固界面电荷积聚导致的沿面闪络问题，是制约其发展的瓶颈，也是新型环保混合气体在应用时面临的重要挑战。本项目重点围绕C4F7N混合气体(即g3气体)在直流设备中应用时需掌握的关键放电参数、绝缘性能、气固界面特性等开展研究，主要研究内容和关键结果如下：（1）搭建了脉冲汤逊实验平台，测量获得了C4F7N、C4F7N/CO2混合气体等新型环保气体的电子群参数，通过临界击穿场强和直流击穿实验评估了新型环保气体的绝缘性能；（2）搭建了直流GIL缩比绝缘子表面电荷测量平台，测量获得了C4F7N/CO2混合气体中气固界面电荷时空演化规律，发现C4F7N/CO2混合气体与SF6气体中气固界面电荷积聚特性存在显著差异并分析了其主要原因；（3）研究了表面电荷极性和位置对沿面放电的影响规律，重点分析了表面电荷的场畸变效应和种子电荷效应，揭示了气固界面电荷对沿面放电的诱导机制；（4）建立了直流GIL多场耦合仿真模型，研究了绝缘结构对气固界面电荷和电场的影响规律，获得了最优的±550 kV直流GIL盆式绝缘子几何结构；提出了一种PVA/MMT二维纳米涂层技术，可以达到使表面电荷均匀、提高沿面闪络电压的效果。本研究为新一代环保型直流GIL的研发提供了重要参考。