Dew condensation may cause switchgear accidents

and temperature and humidity are both the main factors causing dew condensation. In this paper

following the conservation laws of energy

momentum

mass and component

a mathematical model of the temperature and humidity fields in cable room of a high-voltage switchgear is established with consideration of heat conduction

air convection and water vapor diffusion. The finite element software Comsol is used to conduct numerical calculation in order to reveal the distributions of temperature and humidity as well as the relationship of dew condensation with temperature and humidity. Results show that:（1）cable has the highest temperature owing to its self-heating

and air temperature in cable room gradually increases under the effects of heat conduction and convection;（2）humidity distribution is influenced by both water vapor diffusion and temperature;（3）the humidity increases at first

then decreases

in contrast with the temperature;（4）the greater the temperature difference or the higher the relative humidity is

the more possibly the dew condensation produces. Finally

according to the simulation results

some countermeasures against dew condensation are offered for engineering.