The low-voltage electrical appliances in the distribution box caused by the influence of the environment temperature on the low-voltage electrical appliances are composed of fuse, AC contactor, residual current action protector, capacitor and meter, etc.

These low-voltage electrical appliances are designed and manufactured according to the basic standard for low voltage electrical appliances, and their normal working conditions are specified accordingly: the upper limit of ambient air temperature is not more than 40 ℃; the average value of ambient air temperature for 24 hours is not more than 35 ℃; the lower limit of ambient air temperature is not less than - 5 ℃ or - 25 ℃.

The distribution box of rural power grid transformation operates outdoors. It not only generates high temperature by direct sunlight, but also generates heat in operation. Therefore, in the hot summer season, the temperature in the box will reach more than 60 ℃, which greatly exceeds the specified ambient temperature of these electrical appliances. Therefore, the failure caused by overheating of electrical components in the distribution box will occur.