1. Faults caused by the influence of ambient temperature on low-voltage electrical appliances The low-voltage electrical appliances in the distribution box are composed of fuses, AC contactors, residual current action protectors, capacitors and meters. These low-voltage electrical appliances are designed and manufactured in accordance with GB1497 "Basic Standards for Low-Voltage Electrical Appliances", and their normal working conditions are specified: the upper limit of ambient air temperature does not exceed 40 °C; the average value of ambient air temperature of 24 h does not exceed 35 °C The lower limit of the ambient air temperature is not lower than -5 ° C or -25 ° C. The power distribution box reconstructed by the rural power grid is operated outdoors. It is not only exposed to direct sunlight, but also generates heat during operation. Therefore, during the hot summer season, the temperature inside the box will reach 60 °C or above. The temperature greatly exceeds the ambient temperature specified by these appliances, and malfunctions due to overheating of electrical components in the distribution box may occur.
2, the failure caused by product quality in the rural network transformation at that time due to the large number of distribution boxes required, the construction period is short, the distribution box factory needs the supply of low-voltage electrical appliances in an urgent and large number, resulting in product quality The phenomenon of not strict requirements has caused some electrical equipment to fail soon after it is put into operation. If some types of AC contactors are not put into operation after the switchboard is put into operation, the contactor closing coils will burn out and cannot operate.
3. Faults caused by improper selection of electrical appliances in the distribution box. Due to the improper selection of the AC contactor capacity during manufacturing, the AC contactors of the same capacity are installed for different outlet circuits, and the imbalance of the three-phase load is not considered. However, it is not possible to increase the current level of some of the line contactor current levels based on the normal selection model, thus causing the AC contactor to burn out during the summer high temperature season.