Causes of electrical apparatus failure in Small Distribution Board

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

The low-voltage electrical apparatus in the Small Distribution Board is composed of miniature circuit breaker, residual current operated protector, etc. These low-voltage electrical apparatus are designed and manufactured in accordance with the basic standard for low voltage electrical apparatus, and their normal working conditions are specified accordingly: the upper limit of ambient air temperature shall not exceed 40 ℃; The average value of ambient air temperature in 24h shall not exceed 35 ℃; The lower limit of ambient air temperature shall not be lower than -5 ℃ or -25 ℃.

The Small Distribution Board of rural power grid transformation operates outdoors. It is not only exposed to the direct sunlight to generate high temperature, but also generates heat during operation. Therefore, in the high-temperature season in midsummer, the temperature in the box will reach more than 60 ℃. At this time, the temperature greatly exceeds the specified ambient temperature of these electrical appliances, so the fault caused by overheating of electrical components in the Small Distribution Board will occur.

1.2 faults caused by product quality

During the transformation of rural power grid, due to the large number of Small Distribution Boards required and the short construction period, the Small Distribution Board factory needed a large number of low-voltage electrical appliances, so the requirements for product quality were not strict, resulting in the failure of some products shortly after they were put into operation.

1.3 faults caused by improper selection of electrical appliances in the Small Distribution Board

As the capacity of circuit breaker was not properly selected during manufacturing, circuit breakers with the same capacity were installed for different outgoing circuits, and the imbalance of three-phase load was not taken into account, and the current level of some outgoing circuit breakers was not increased by one current level on the basis of normal model selection, resulting in circuit breaker burnout during operation in high temperature season in summer.