Research On Breakdown Characteristics And The Spectral Characteristics At Discharge Of SF₆/N₂ Mixtures

Gas insulated switchgear equipment is widely used in the electric power system, the insulation of the equipment has been a very serious problem, SF₆ is widely used in gas insulated equipment due to the characteristics of high dielectric strength and strong arcing ability. Due to the SF₆ takes shortcomings of strong greenhouse effect and high liquefaction temperature, a research boom on SF₆ alternative gas becomes a global scale spark. Dry air or N₂ possesses limited insulation ability, and has obvious polarity effect, the development of miniaturization of devices is limited. In order to make the equipment smaller and reviewing environmental impact to a minimum under the premise of good insulation, research on SF₆/N₂ mixed gasis are carried out in this paper, and guidance suggestion is put forward to engineering practice.In this paper, based on the high- voltage SF₆ gas insulated equipment, the spectral characteristics of the design of an experimental model of SF₆ insulation and SF₆/N₂ plasma discharge arc wasprocessed. By measuring SF₆ and SF₆/N₂ gas mixture in the plate, the breakdown voltage board is under analysis insulating properties of the mixed gas, finding the best mixing ratio. By using spectral information spectrometer plate electrode arc plasma to analyze different percentages of SF₆ gas mixture at different electrode spacing, wavelength, light intensity and FWHM parameter information, the spectral information, the electron temperature and electron density under different pressures with variation of parameters such as changes in the relationship between the conductivity electrode spacing and the gas pressure are achieved, and the derivation and calculation of ions are also conducted; by measuring breakdown voltage of rod plate electrode polarity under analysis, SF₆ and SF₆/N₂ gas mixture polar effect has obtained.The results showed that: SF₆ and N₂ mixed gas has good insulating properties, breakdown voltage and gas pressure of SF₆ and SF₆/N₂ mixture gas and plate gap are from the linear relationship. When the mixed gas SF₆ percentage is only 20%, the breakdown voltage can be achieved under the same conditions of 72% pure SF₆ gas. Holding plate spacing unchanged at 0.1MPa-0.4MPa under SF₆ and SF₆/N₂ mixed gas,when gas was completely breakdown, measuring light intensity, the electron density and conductivity parameters gradually increased as the pressure increases, and the electronic temperature decreases. Ma intaining gas pressure constant, the light intensity of SF₆ and SF₆/N₂ mixture gas gradually increasedas the complete breakdown of plate spacing increases, while the electron temperature, electron density and conductivity were essentially unchanged; With the percentage of SF₆ gas mixture is gradually increased, the light intensity increased, electronic temperature gradually increased, the electron density and conductivity decreased whenSF₆/N₂ mixed gas was completely breakdown. Under stick plate electrodenon-uniform electric field, the breakdown voltage of negative polarity of N₂ is higher than positive breakdown voltage, and SF₆ gas having opposite polarity effect to N₂ showed the breakdown voltage of positive polarity slightly higher than the breakdown voltage of negative polarity.With theproportionof SF₆ gas in the mixed gas decreased, polarity effecthas reversed. As pressure increases, the breakdown voltage of positive polarity is saturated effect, hump effect appears at 0.25MPa-0.4MPa pressure. Proposed idea of using low concentration of SF₆/N₂ mixed gas insulation in the medium pressure gas insulation switch, and provide experimental support and guidance to engineering practice.