Construction site distribution line cable selection requirements

(1) Cable type selection

The cable must contain all working cores and cores used to protect the neutral or protective wires. A five-core cable must be used for cable lines requiring three-phase four-wire power distribution. The five-core cable must include insulated core wires of light blue and green/yellow. The light blue core wire must be used as the N wire. The green/yellow core wire must be used as the PE wire. It is strictly prohibited to mix. Cable lines should be laid underground or overhead, and it is strictly forbidden to be installed along the ground. Mechanical damage and media corrosion should be avoided. The buried cable path should be marked with an azimuth. Cables should be selected according to the laying method and environmental conditions. The buried cable should be armored cable; when the armored cable is selected, it should be waterproof and anticorrosive. Unarmored cables should be used for overhead laying.

(2) Section selection

The choice of cable cross section should be determined based on its long-term continuous load allowable current carrying capacity and allowable voltage offset.

(3) laying method

1. Buried laying

(1) Buried laying facilities: The buried depth of the cable should not be less than 0.7m, and fine sand of not less than 50mm thick should be evenly laid on the upper, lower, left and right sides of the cable. Then cover a hard protective layer such as brick or concrete slab.

(2) Buried laying protective casing: buried cables must be installed with protective casings when crossing buildings, structures, roads, mechanical damage, medium corrosion, and grounding from 2.0m to 0.2m underground. The outer diameter of the casing is not less than 1.5 times the inner diameter of the cable.

(3) Laying the safety distance: The parallel distance between the buried cable and its external electrical cable and pipe trench shall not be less than 2m, and the intersection spacing shall not be less than 1m.

(4) Handling of buried cable joints: The joints of buried cables should be placed in the junction box on the ground. The junction box should be waterproof, dustproof and mechanically resistant, and should be kept away from flammable, explosive and corrosive places. .

2, overhead laying

(1) Overhead coating facility technology: overhead cables should be laid along poles, brackets or walls, and fixed by insulators. The binding wires must be insulated wires. The spacing between fixed points should ensure that the cables can withstand the load brought by themselves. Meet the requirements, but the maximum arc offset when laying along the wall shall not be less than 2.0m.

(2) Cable laying, decoration and construction electricity in construction in progress

The cable lines within the construction in progress must be buried by cables and must not be introduced through the scaffolding. The vertical laying of cables should make full use of the shafts, vertical holes, etc. of the construction in progress, and should be close to the center of the electric load. The fixed points must not be less than one floor per floor. The horizontal laying of the cable should be rigidly fixed along the wall or the doorway, and the maximum arc offset should not be less than 2.0m. In the decoration and decoration project or other special stages, a single construction electricity plan should be supplemented. The power cord can be laid along the corner and the ground, and should be protected against mechanical damage and electric fire.

(4) Ways of protection

Cable lines must have short circuit protection and overload protection.