稍不均匀场下CF_4/N_2混合物雷电冲击绝缘特性研究

Breakdown Characteristics of CF_4/N_2 in Slightly Non-uniform Electric Field Under Lightning Impulse Stress

减少SF_6温室气体的使用,对绿色电网有重要意义。目前对SF_6替代气体的研究主要集中在常温环境下,对能够在极寒地区使用的替代气体研究还不多。CF_4具有明显的电负性,同时液化温度较低。文中在稍不均匀电场下、正负两种极性雷电冲击作用下,研究了CF_4及其N_2混合物绝缘特性。研究结果表明:CF_4/N_2混合气体击穿电压随混合比增加有明显的饱和效应,20%混合气体具有较低液化温度和GWP指数,同时绝缘强度良好,具备在极寒地区使用的潜力;通过对混合气体的协同效应分析发现:CF_4/N_2混合气体协同效应随气压升高而变得明显,CF_4/N_2负极性雷电冲击条件下协同效应比正极性雷电冲击条件下为显著,协同系数小于0.4。

Reducing the usage of SF6 is important to a green power grid. Recent research on SF6 replacement focuses on gas behavior at room temperature and there has been little work on the use of replacement gas in extremely cold regions. CF4, which has a low liquefaction temperature, is strongly electronegative. The insulation characteristics of CF4 and its N2 mixture in slightly non-uniform electric field has been studied under the stress of positive and negative lightning impulses. Results show that the breakdown voltage of CF4/N2 mixture increases with the mixing ratio but reaches saturation fairly quickly. The mixture with 20% of CF4 has very good insulation strength, low GWP value and low liquefaction temperature. It is potentially a good candidate for use in extremely cold environment. Moreover, the synergistic effect of binary gas mixture is analyzed and results shown that pressure has positive contribution towards the synergistic effect. The synergistic effect of CF4/N2 mixture with negative lightning impulse stress is stronger than that with positive lightning impulse stress, with the synergistic coefficient being less than 0.4.