Abstract: As one of the factors that affect the reliability of the power system, the condensation phenomenon seriously threatens the safe operation of electrical equipment. An experiment system of ring main unit (RMU) is set up in an artificial climate chamber, and the formation time of condensation on the cabinet inner wall is recorded under different conditions of full ventilation, half ventilation and non-ventilation of the RMU's shell with different ambient temperatures and relative humidity. The results show that, when the ambient humidity is constant within a certain temperature range, the formation time of condensation under ventilation is longer than that under non-ventilation, and the half ventilation has the longest condensation time. When the ambient temperature reaches a certain value, the ventilation, however, can stimulate the formation of condensation. With the increase of ambient temperatures, the formation time of condensation increases before decreasing, and the lower the relative humidity, the better the ventilation effects are. A suitable ambient temperature and ventilation area can make the better effects of anti-condensation under ventilation.

Key words: ring main unit, ventilation, temperature, humidity, condensation time