What are the requirements for the first-class electrical box protection on the construction site?

The main distribution box is the centralized point for controlling all power sources on the construction site and should be set near the power supply area. The protection circuit is used to prevent external circuit failure provided by the distribution box. Choose a small intelligent phase-break protector and install it in the distribution box to prevent low-voltage phase-break operation from burning out the motor.

The power supply is connected by the cable led from the low voltage side of the power transformer on the construction site, and the current transformer, active watt-hour meter, reactive watt-hour meter, ammeter, voltmeter, main switch and sub-switch are installed. The switches in the main distribution box shall be breaker switches (or leakage protection switches). Lead-in and lead-out wires should pass through the pipeline and have waterproof bends.

Temperature control relay (JU-3 or JU-4 subminiature temperature relay) and axial fan should be installed on the side wall near the cooling window in the box body, and on the box body at the upper left of the control panel, so that when the temperature in the box body reaches a certain value (such as 40℃), the exhaust fan can be automatically started to forcibly discharge heat and cool the box body.

Extended data:

Pay attention to the following points when using the distribution box.

1. The construction power distribution system is provided with a main distribution box, a distribution box and a switch box, which are arranged in layers in the order of "main-sub-open" to form a "three-level power distribution" mode.

2. The installation position of distribution box and switch box in the construction power distribution system should be reasonable. The main distribution box should be as close as possible to the transformer or external power supply to facilitate the introduction of power supply. The distribution box should be installed in the center of electrical equipment or where the load is relatively concentrated as far as possible to ensure the balance of three-phase load. The installation position of the switch box should be as close as possible to the electrical equipment controlled by it according to the field situation and working conditions.

3. In order to ensure the three-phase load balance of the temporary power distribution system, the power supply and lighting power supply at the construction site should form two power supplies, and the power distribution box and lighting distribution box should be set separately.

4, all the electrical equipment on the construction site must have their own dedicated switch box.

5. The boxes and internal settings of distribution boxes at all levels must comply with safety regulations, and the switch appliances should be marked with the purpose, and the boxes should be numbered uniformly. When stopping using the distribution box, cut off the power supply and lock the door. The fixed distribution box should be fenced to prevent rain and smashing.

Baidu encyclopedia-main distribution box

Baidu Encyclopedia-Distribution Box (Electrical Equipment)