1. The power distribution system at the construction site shall implement hierarchical power distribution, which shall be equipped with a general distribution box (or distribution room), a distribution box below the general distribution box, a switch box below the distribution box, and electrical equipment below the switch box.

2. The main distribution box shall be set in the area close to the power supply; the distribution box shall be set in the area where the electrical equipment or loads are relatively concentrated; the interval between the distribution box and the switch box shall not exceed 30m; the switch box shall be distributed by the final distribution box, and the horizontal interval between the switch box and the fixed electrical equipment controlled by it shall not exceed 3M

3. Distribution box and switch box shall be installed in ventilated, dry and normal temperature places. It is strictly prohibited to install it in the gas, flue gas, steam, liquid and other harmful media with severe damage effect, and it is not allowed to install it in the place that is easy to be hit, vibrated, splashed by liquid and baked by heat source; there should be space and channel around the distribution box and switch box that can meet the requirements of two people working together, and no objects that hinder operation and repair should be stacked, and there should be no weeds, shrubs, etc.

4. The distribution box and switch box shall be made of iron plate or high-quality insulating material, and the thickness of iron plate shall be greater than 1.5mm; the electrical appliances in the distribution box shall be installed on the metal or non wood insulating electrical device plate, and then all of them shall be fastened in the distribution box; the metal plate and distribution box shall be electrically connected.

5. The connecting line in the distribution box and switch box shall be insulated wire, the joint shall not be loose, and there shall be no exposed electrified part; the working zero line in the distribution box and switch box shall be connected through the terminal board, and shall be set separately with the maintenance zero line terminal board; it is necessary to do the following for the metal box, metal electrical device board of the distribution box and switch box, and the non electrified metal base and shell of the electrical appliances in the box The maintenance neutral line shall be connected through the terminal block.

6. Power distribution box and lighting distribution box should be set separately. If they are in the same distribution box, power and lighting lines should be set separately.

7. The wire inlets and outlets in the distribution box and switch box shall be set at the lower bottom of the box. It is strictly prohibited to set them at the top, side, back or door of the box. The inlets and outlets shall be bundled with sheath and made with waterproof bends. The wire bundle shall not be directly touched with the inlets and outlets of the box. The power lines entering the switch box shall not be connected with pins. The power lines of the mobile distribution box and switch box shall not be connected with pins It is necessary to select rubber insulated cables for import and export wires.

8. The distribution box and switch box shall be installed firmly and regularly. The mobile distribution box and switch box shall be installed on the consolidated support. The vertical interval between the lower bottom of the fixed distribution box and switch box and the ground shall be greater than 1.3m and less than 1.5m. The vertical interval between the lower bottom of the mobile distribution box and switch box and the ground shall be greater than 0.6m and less than 1.5m. All distribution boxes and switch boxes shall be rainproof , dustproof.