Discussion On Common Faults Of Power Distribution Cabinets Based On Practical Experience

Any equipment will have more or less faults during use, and High And Low Voltage Distribution Cabinets is no exception.

1.1 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. The upper limit of the ambient air temperature does not exceed 40℃; the average value of the ambient air temperature for 24 hours does not exceed 35℃; the lower limit of the ambient air temperature is not lower than -5℃ or -25℃.

The distribution box for rural power grid transformation is operated outdoors. It is not only directly exposed to the sun to generate high temperature, but also generates heat during operation. Therefore, in the hot summer season, the temperature in the box will reach more than 60℃, which greatly exceeds the ambient temperature specified by these electrical appliances.

1.2 Faults caused by product quality

In the rural power grid transformation, due to the large number of distribution boxes required and the short construction period, the distribution box factory needed to deliver the relevant low-voltage electrical appliances in a hurry and in large quantities, which resulted in the phenomenon of lax requirements on product quality, causing some products to fail shortly after they were put into operation. For example, some models of AC contactors cannot operate soon after the distribution box is put into operation because the contactor closing coil burns out.

1.3 Faults caused by improper selection of electrical appliances in the distribution box

Due to the improper selection of the capacity of the AC contactor during manufacturing, the same capacity AC contactors are installed for different outgoing line circuits, and the imbalance of the three-phase load is not taken into account, and the current level of some outgoing line contactors cannot be increased by one current level on the basis of the normal selection model.

Based on actual work experience, the following points are discussed:

1. Imported distribution cabinets are developed abroad and are generally sold to the global power supply and distribution market. Since each country has different requirements and habits for the power supply and distribution system, imported distribution cabinets may not be completely applicable to the domestic market.

2. The main electrical components used in imported distribution cabinets are all imported brand products, and some cabinets or some cabinet accessories must be imported from abroad, which makes the price of imported distribution cabinets generally much higher than that of domestic distribution cabinets.

3. Although the technical parameters of imported distribution cabinets are very high, in most cases only a part of them are used, or even not used at all. For example, an imported distribution cabinet can install more circuits than a domestic distribution cabinet, but that can only be achieved under the premise of reducing the circuit capacity, which cannot meet the needs of users in most cases.

4. Although the technical parameters of domestic distribution cabinets are lower than those of imported distribution cabinets, they can already meet the needs of users in most domestic power supply and distribution systems.

5. In terms of the quality of distribution cabinets, as long as the manufacturer strictly follows the requirements of 3C for production and inspection, the quality of domestic distribution cabinets is not necessarily worse than that of imported distribution cabinets.