Indoor low-voltage cables refer to wires (conductors) and cables installed indoors to transmit low-voltage alternating current. The indoor voltage is mostly 220V or 380V, the former is used for lighting and household appliances, and the latter is mostly used for three-phase power equipment. The two have different uses, but the selection principles and methods of power supply lines and cables are the same. The selection of indoor cables should mainly consider the following four aspects.

1. Sufficient mechanical strength and flexibility

Must have sufficient mechanical strength and flexibility. The mechanical strength is too small to withstand the stretching force of people, and it is easy to break. When using the concealed installation method, the cable must pass through the pipe fixed in the wall. If the mechanical strength is insufficient, the core wire may be broken during the threading process. Therefore, the fixed cable of the exposed or concealed installation should use a copper core. or aluminum core wire.

The power cord of household appliances or the lead-in line of temporary socket, because it is often pulled out and moved, the flexibility of the cable should be considered, and generally multi-strand copper core wire should be used.

2. Insulation

The insulation performance of the cable is an important indicator to ensure the safe use of electricity. There are two types of insulation sheaths for commonly used cables: rubber and plastic. Rubber insulated conductors are mostly used in situations where the AC rated voltage is below 250V and the long-term operating temperature does not exceed +60°C. The plastic insulated wire can be used in the occasions where the AC rated voltage is below 500V or the DC voltage is below 1000V, and the working temperature for a long time does not exceed +65°C.

3. Conductivity

The conductivity of copper wire is higher, followed by aluminum wire. Under the same resistance, the cross-section of aluminum wire is 1.68 times that of copper wire, and the mechanical strength of copper wire is higher than that of aluminum wire; aluminum wire is cheaper and difficult to weld. .

Fourth, the cross-sectional area of the cable

Correctly selecting the conductor cross-sectional area of the cable is one of the important measures to ensure safety, reliability and economy. The conductor cross-sectional area is also an important indicator for selecting cables.

The safe current carrying capacity of the cable mainly depends on the material and cross-sectional area of the conductor. After the conductor material is determined, the cross-sectional area is the first issue that should be considered. The higher the conductivity and the larger the cross-sectional area of the conductor in the cable, the greater the safe current-carrying capacity, which is also related to the insulation material, laying method, and ambient temperature of the cable. In a large number of practices that fully consider the above factors, people have summarized and formulated the safe current carrying capacity of the commonly used cables and then look up the table.