1. Selection of electric wire and cable model (1) When […]
1. Selection of electric wire and cable model
(1) When selecting wires and cables, consider the purpose, laying conditions and safety;
(2) According to different purposes: power cables, overhead insulated cables, control cables, etc. can be selected;
(3) According to the different laying conditions: general plastic insulated cables, steel tape armored cables, steel wire armored cables, anti-corrosion cables, etc. can be selected;
(4) According to safety requirements: flame-retardant cables, halogen-free flame-retardant cables, fire-resistant cables, etc. can be selected.
2. Selection of wire and cable specifications
(1) When determining the use specifications of wires and cables (conductor cross-section), heat generation, voltage loss, economic current density, mechanical
Strength and other conditions.
(2) Because of the large load current of the low-voltage power line, generally select the cross section first according to the heating conditions, and then check the voltage loss and mechanical strength;
(3) Because of the high voltage level requirements of the low-voltage lighting line, the section can be selected according to the allowable voltage loss condition, and then the heating condition and mechanical strength can be checked;
(4) For high-voltage lines, first select the cross section according to the economic current density, and then check the heating conditions and allowable voltage loss.
A cable is usually a rope-like cable formed by twisting several or several groups of wires [each group of at least two wires]. Each group of wires are insulated from each other and often twisted around a center. The entire outer bread has a height Insulating covering layer. They are mostly erected in the air or installed underground or underwater for telecommunications or power transmission.
An insulated wire composed of one or more mutually insulated conductive cores placed in a sealed sheath. A protective covering layer can be added to transmit, distribute electric energy or transmit electrical signals. The main difference between it and ordinary wires is that the cable size is larger and the structure is more complicated.
Cables can be divided into power cables, communication cables and control cables according to their uses. Compared with overhead lines, cables have the advantages of small insulation distance between lines, small footprint, underground laying without occupying space above the ground, not affected by environmental pollution, high power transmission reliability, and interference with personal safety and the surrounding environment. small. However, the cost is high, construction and maintenance are troublesome, and the manufacturing is also complicated.