The paper is devoted to comparing the characteristics of SF6 and alternative environmentally friendly mixtures as insulating and arc extinguishing media in high-voltage circuit breakers. It is considered several mixtures based on CO2, N2, air and SF6 as well as their main electrical parameters. A comparative analysis of the dielectric and arc-extinguishing properties of proposed alternative gases is carried out according to the main physical characteristics - the most promising mixture C4F7N/CO2 (Novec 4710) is chosen. An analytical calculation of insulation gaps and gas-dynamic characteristics for SF6 and the alternative chosen is performed. A numerical calculation of the electric fields - 'electrostatics' study in COMSOI Multiphysics software for the 110 kV live-tank circuit breaker with SF6 insulation media and the one under study is carried out. It is shown that the proposed alternative based on C4F7N/CO2 is no worse than SF6 as not only an insulating media but also an arc extinguishing one with the minimal global warming potential. © 2023 IEEE.