Study On Power Fequency Breakdown And Partial Discharge Characteristics Of HFO/SF₆ Gas Mixture

SF₆gas has good insulation performance,but because of its strong greenhouse effect,it is urgent to find a replacement of SF₆gas.At present,the alternative method of SF₆gas is mainly mixed gas.In this scheme,mixed gas with strong positive synergistic effect has obvious inhibition on the development of electron collapse,which is the most ideal alternative method.It is found that the mixing of the new environmental protection insulating gas HFO and SF₆gas presents a strong positive synergistic effect under low pressure.In order to explore the feasibility of HFO/SF₆gas mixture replacing SF₆gas under the operating conditions of power equipment,the thesis takes the air pressure,mixing ratio and electrode spacing under different electric fields as variables.The power frequency breakdown characteristics,partial discharge characteristics and cooperative relationship of HFO/SF₆gas mixture were studied.In order to study the dielectric strength of HFO/SF₆gas mixture under the action of power frequency voltage,the power frequency breakdown voltage test of HFO/SF₆gas mixture under slightly uneven and non-uniform electric field was carried out in the laboratory.The results show that,under slightly uneven electric field,the power frequency breakdown voltage of HFO/SF₆gas mixture with low electrode spacing increases with the increase of air pressure,while the power frequency breakdown voltage of HFO/SF₆gas mixture with high electrode spacing becomes saturated with the increase of air pressure.With the increase of HFO proportion,HFO/SF₆gas mixture presents a strong positive synergistic effect,and the strongest positive synergistic effect is presented when the HFO gas proportion is80%.Through comparison test,it is found that the power frequency breakdown voltage of HFO/SF₆mixture is higher than that of SF₆/N₂mixture when external conditions are fixed.Under a highly uneven electric field,the breakdown voltage of the power frequency of HFO/SF₆gas mixture presents an N-shaped curve with the increase of air pressure.At the same time,this thesis carried out an experimental study on the partial discharge characteristics of HFO/SF₆gas mixture under the action of power-frequency voltage in the laboratory.With SF₆/N₂gas mixture as the reference object,the influence law of positive and negative polarity on the initial partial discharge voltage of HFO/SF₆gas mixture was analyzed.The test results show that the positive and negative half-cycle initial voltages of HFO/SF₆and SF₆/N₂mixtures increase with the increase of air pressure and electrode spacing.On the whole,the initial partial discharge voltage of HFO/SF₆mixture in positive and negative half cycles is much higher than that of SF₆/N₂.In addition,the HFO/SF₆mixture showed strong positive synergistic effect when the HFO ratio was 20%and 80%.Considering the power frequency breakdown and partial discharge characteristic test of HFO/SF₆gas mixture,this thesis proposes that 80%HFO/20%SF₆gas mixture can be used as SF₆alternative gas in electric industry.