Matters needing attention in the operation of low-voltage distribution box

1. The high temperature causes the service life of the electrical equipment of the distribution box to decrease
The upper limit of the ambient temperature of the electrical equipment designed and manufactured according to the national standard should not exceed 40 °C, and the operating distribution box exposed to the hot sun in summer, because of the direct sunlight, the reflection of the heat on the cement floor and the equipment inside the box. The heat generated by itself, sometimes the temperature in the box exceeds 60 ℃. Such a high temperature can easily cause the insulation of electrical coils and leads to be aged and burn out; the electrical contacts will increase contact resistance due to the high temperature, which will cause the contacts to burn out; at the same time, the high temperature will also affect the electrical protection function. stability, reliability of action, and accuracy of measurement.

2. Only install the arrester on the incoming line side, and the lightning protection cannot cover the whole equipment
Usually, fuses and other equipment are installed between the incoming and outgoing lines of the distribution box and their bus bars. When the outgoing line is struck by lightning, if the incoming line fuse is blown first, all the distribution boxes will lose lightning protection. The distribution box was damaged by lightning strikes.

3. Improper installation process, causing overheating and burning of the connector
Some electricians do not crimp the wire nose when changing the lead wire, but use multi-stranded wire to wrap the wire nose and screw it. As a result, the lead wire is blown shortly after the wire is changed. The distribution box produced by some manufacturers is connected to the bus by stacking and screwing. If the heat dissipation is not good, it will be overloaded and cause continuous failures.

4. The distribution box is put into use without inspection, leaving hidden dangers to safety
The products will be strictly inspected when they leave the factory. However, due to bumps in the road and vibration during loading and unloading, some connecting bolts may be loosened to a certain extent after arriving at the site, resulting in the overheating of the lead connectors soon after the distribution boxes are put into operation. 

6. Pay attention to the three-phase four-wire power supply mode
Some power supply systems with protection connected to zero still use the three-phase four-wire power supply mode. The zero line of the low-voltage power grid is long and the impedance is large. When the three-phase load is unbalanced, the zero-sequence current will pass through the zero line. At the same time, due to the deterioration of the environment , wire aging, damp and other factors, the leakage current of the wire also forms a closed loop through the zero line, resulting in a certain potential on the zero line, which is very unfavorable for safe operation.
  
7. The size of the distribution box is incorrect
The distribution box interval is too small, the gap between electrical appliances and between phases is small, and some have no obvious disconnection point, which not only brings danger to electrician operations, but also makes it impossible to replace fuses with electricity in rainy and foggy weather. work the distribution box generally lacks phase loss protection, and accidents that burn out the electromechanical due to lack of phase often occur some distribution boxes do not use electronic energy meters, so remote centralized meter reading cannot be implemented; some distribution boxes are closed all the year round. However there is a lack of security inspection protection.