Research On The Surface Discharge Properties Of C-C₄F₈ And Its Mixed Gas

SF₆ has good insulation and arc performance,which is a very good gas insulation medium,widely used in high-voltage power equipment.However,extensive use of SF₆ will bring serious greenhouse effect,and people are looking for SF₆ alternatives.Of all possible SF₆ alternative insulating gases,c-C₄F₈ and its mixtures have good potential.However,the study of the insulation properties of c-C₄F₈ and its mixtures is not comprehensive.The gas insulation properties in slightly non-uniform electric field and the flashover characteristics of insulators are still not know clearly and need be studied further.In this paper,the insulation properties of c-C₄F₈ and its mixtures are systematically studied.We have done gas gap insulation experiment of slightly non-uniform electric field and insulator flashover experiment about c-C₄F₈,c-C₄F₈/N₂ and c-C₄F₈/CO₂.First of all,the experiment device and experiment method are introduced,then the liquefaction temperature of c-C₄F₈ mixed gases are calculated under different pressures,then gas breakdown experiment and flashover experiment in insulators are done,compared with N₂?CO₂?SF₆.Experimental results show that,the breakdown voltage of mixtures increases as the gas pressure/gap length/ratio of c-C₄F₈ increases;In slightly nonuniform field,insulation performance of 30%c-C₄F₈/N₂ and c-C₄F₈/CO₂ mixed gas equals to 75%and 79%of pure SF₆ in 0.10 Mpa;the synergistic effect coefficients of c-C₄F₈/N₂ and c-C₄F₈/CO₂ in 5%³0%mixing ratio are between 0.20⁰.79 and 0.15⁰.65 respectively.For surface falshover,pressure and ratio of c-C₄F₈ are critical influence factor.The flashover performance of c-C₄F₈/N₂ and c-C₄F₈/CO₂ will improve with pressure and ratio of c-C₄F₈ enhancing.The surface flashover performance of c-C₄F₈/N₂ and c-C₄F₈/CO₂ also has little difference.At the same time,the insulator coefficient is calculated,the insulator coefficient of c-C₄F₈/N₂ is between 0.40⁰.65 and the insulator coefficient of c-C₄F₈/CO₂ is between0.40⁰.69.The flashover performance of c-C₄F₈/N₂ and c-C₄F₈/CO₂ are73%and 80%of SF₆.The influence of gas pressure,voltage type,gas mixing ratio and air gap distance on the insulation properties of c-C₄F₈mixed gas is analyzed.The decomposition products of c-C₄F₈ and its mixtures are also analyzed.The mixed gas insulator flashover characteristics are and analyzed which will provides useful guidance in practical application.