Failure analysis of stainless steel distribution box

The reason of electrical breakdown of stainless steel distribution box

1.1 faults caused by the influence of ambient temperature on low-voltage electrical appliances

The low-voltage apparatus in the stainless steel distribution box is composed of fuse, AC contactor, residual current action protector, capacitor and meter. These low-voltage electrical appliances are designed and manufactured in accordance with gb1497 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 stainless steel distribution box reconstructed by rural power grid 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, it will be caused by overheating of electrical components in the stainless steel distribution box Of.

1.2 during the transformation of rural power grid, due to the large number of stainless steel distribution boxes and short construction period, the stainless steel distribution box factory needs a large number of low-voltage electrical appliances, which leads to the phenomenon that the requirements for product quality are not strict, resulting in the failure of some products shortly after they are put into operation. For example, some types of AC contactors can not operate because the closing coil of the contactors is burnt out soon after the stainless steel distribution box is put into operation.

1.3 faults caused by improper selection of electrical appliances in stainless steel distribution box Due to the improper selection of AC contactor capacity in manufacturing, the installation of AC contactors with the same capacity for different outgoing circuits without considering the imbalance of three-phase load, and the failure to improve the current level selection of some outgoing contactors based on the normal selection of models, resulting in the burnout of AC contactors during operation in high temperature seasons in summer situation.