During the long-term operation of electrical equipment, the insulation performance of applied SF6 gas may be affected by humidity, pressure, and temperature. In this study, the collision cross sections of SF6 and H2O are considered, including ionization, attachment, excitation, and elastic collision. In order to analyze the influencing factors of SF6 insulation performance, discharge parameters are computed by the Boltzmann equation under different environmental conditions, including humidity, pressure, and temperature. It is concluded that with the conditions of 0.1 MPa and 300 K, the critical breakdown electric field increases by 1.23 kV/cm as the relative humidity increases from 0% to 80%. As the pressure increases from 0.1 to 0.6 MPa, the critical breakdown electric field increases by 451.07 kV/cm. However, temperature also has little effect on the insulation performance of SF6 gas. The conclusions of this study have reference value for safe and stable operation of SF6 insulated power equipment.

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The environmental conditions affect the external insulation performance of power equipment. In order to study the physical characteristics of air discharge, the microscopic process of electron–molecule collision in the air based on the Boltzmann equation has been studied in this paper. The influence of humidity on the air gap insulation performance was also analyzed. The calculation results show that with the temperature 300 K and the pressure 1.0 atm, the electron energy distribution function and electron transport parameters varied with the air relative humidity. As the air relative humidity is increased by each 30%, the average electron energy decreases by about 0.2 eV, the reduced electron mobility decreases by about 0.25 × 1023 [1/(V·m·s)], the reduced electron diffusion coefficient decreases by about 0.2 × 1024 [1/(m s)], and the effective ionization coefficient decreases by about 4 × 10−24 m2. As the air relative humidity increases from 0% to 60%, the critical breakdown electric field increases by 1.22 kV/cm.

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