The distribution box consists of a distribution box base and a guide rail. The two sides of the distribution box base are separated and tightly connected by the base fasteners. The guide rail slot seat is clamped in the slot of the base fastener. The guide rail slot seat is provided with several layers of card slots, and both ends of the guide rail are inserted into the card slot. The beneficial function of this product: it can achieve the roughly uniform height of various types of circuit breakers according to the height of the guide rail. It is very convenient to use and can be suitable for various types of circuit breakers. After installation, the appearance is more beautiful, the structure is simple, the function connection is convenient, and the practicability is strong, which is convenient for installation and repair, and convenient for people's life.

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

The low voltage apparatus in the distribution box is composed of fuse, communication contactor, residual current operated protector, capacitor and metering meter. 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 distribution box of rural power network transformation operates outdoors. It not only generates high temperature by direct sunlight, but also generates heat during operation. Therefore, in the high temperature season in summer, the temperature inside the box will reach above 60 ℃, which greatly exceeds the environmental temperature of these electrical regulations

1.2 defects caused by product quality

In the transformation of rural power network, due to the large number of distribution boxes and the short construction period, the distribution box factory needs the supply of low-voltage electrical appliances in a short time and a large number. Therefore, the requirements for product quality are not strict, resulting in problems soon after some products are put into operation. For example, some types of communication contactors can't operate because the closing coil of contactor is burned out soon after the distribution box is put into operation.

1.3 problems caused by improper selection of electrical appliances in distribution box

Because it is not appropriate to select the capacity of the communication contactor during manufacturing. For the communication contactors with the same capacity in different outlet circuit devices, and the unbalanced condition of three-phase load is not considered, the current level of some outgoing line contactors can not be selected on the basis of normal selection type.