The influence of air temperature reduction and temperature change including daily temperature difference
1. Compensation of product temperature rise by ambient air temperature in plateau The average air temperature and maximum air temperature both decrease with the increase of altitude, and the thermal aging life of electrical insulation materials is determined by the average air temperature. The reduction of ambient air temperature on the plateau can partially or fully compensate for the increase in temperature rise of electrical products caused by the reduction of air pressure. The compensation value of ambient air temperature is 0.5K/hm.
2. The impact of daily temperature difference or temperature change on product structure The daily temperature difference of plateau air temperature is large. Larger temperature changes make the product shell easily deformed and cracked, and the sealing structure is easily broken.
3. The influence of the reduction of absolute air humidity
1. The influence of absolute humidity on the external insulation strength
The mean absolute humidity decreases with increasing altitude. When the absolute humidity decreases, the external insulation strength of electrical products decreases, so the humidity correction of power frequency discharge voltage and impulse flashover voltage should be considered. Humidity correction is based on the average absolute humidity at zero altitude: 11g/m3, and the specific correction is in accordance with the relevant regulations in GB311.2.
2. The influence of absolute humidity on motor commutation and carbon brush wear
The reduction of absolute humidity increases the commutation spark of the commutator motor, and at the same time increases the wear rate of the carbon brush of the motor.
4. Solar irradiance, including the effect of increased ultraviolet irradiance
1. The impact of plateau thermal radiation increase
At an altitude of 5000m, the maximum solar irradiance is 1.25 times the corresponding value at a low altitude, and thermal radiation can heat objects. For outdoor electrical products, the increase of solar heat radiation causes a large additional temperature rise on the surface, reduces the material properties of organic insulating materials, deforms materials, and produces mechanical and thermal stress.
2. The impact of increased ultraviolet radiation on the plateau
The increase rate of ultraviolet irradiance with altitude is much larger than the increase rate of total solar irradiance. At an altitude of 3000m, it has reached twice the corresponding value at low altitudes. Ultraviolet light causes accelerated aging of organic insulating materials, which makes the air easy to ionize, resulting in a decrease in external dielectric strength and corona inception voltage.
