The difference between cables and wires and the causes and consequences of power cable heating

Wire and Cable

Wire products used to transmit electric (magnetic) energy, information and realize electromagnetic energy conversion. In the broad sense, wires and cables are also referred to as cables for short. In the narrow sense, cables refer to insulated cables, which can be defined as: a collection composed of the following parts; one or more insulated cores, and their respective possible coatings. Protective layer and outer sheath, the cable may also have additional uninsulated conductors.

cable definition

The cable is made of several wires or groups of wires, which are insulated from each other, twisted around a central wire, and covered with a high degree of insulation. The processing begins with the conductor, and the cable products are wrapped with insulation, shielding, cabling, and sheath on the periphery. The more complex the product structure, the more layers.

wire definition

Wires are conductive metal wires that carry electric current. Wire comes in several forms, stranded or foil braided, etc. According to the insulation condition, there are two types of bare wires and insulated wires. The flexible cylindrical conductor is insulated and the length is larger than its cross-sectional size.

Difference Between Cable and Wire

Cables and wires are mainly composed of three parts, namely the core wire, the insulating sheath and the protective sheath. Wires are made of wires wrapped with a light and soft sheath; cables are made of wires wrapped with metal or rubber as a covering layer, and are mainly used to transmit electrical signals.

As a conductive wire that carries current, wires can be divided into twisted, solid, foil braided, etc. according to the form. According to the insulation condition, it can be divided into bare electricity and insulated electricity. The cable consists of mutually insulated conductive wires placed in a sheath. A surface plus a protective covering, primarily for the transmission, distribution or transmission of electrical signals. The biggest difference in appearance is that the size of the cable is larger and the structure is more complicated, etc., while the size of the wire is smaller and the structure is simpler.

The biggest advantage of the cable is that it occupies less space, and there is little difference in the insulation distance between the lines. If it is laid underground, it will not occupy the space above the ground, and will not be affected by the pollution of the surrounding environment. The power transmission is very reliable and safe, and will not damage Interference with the person and the surrounding environment. Therefore, cables are often used in densely populated and crowded locations, which play a very important role in modernization.

However, when the power cable passes a certain load current, it will definitely generate heat. With the increase of the load current, the surface temperature of the cable will be higher. If it is not handled in time, the consequences can be imagined. For example, for polyvinyl chloride (PVC) cables, the upper limit of the core temperature is 70 degrees, and the surface temperature will be 5 to 10 degrees lower. Therefore, the surface temperature of the cable is basically safe below 60 degrees. From the perspective of power supply maintenance, of course, the lower the temperature, the better.

The reasons for the heating of the cable during operation are as follows:

The cable conductor resistance does not meet the requirements, causing the cable to generate heat during operation.

Improper selection of cables will cause the conductor cross-section of the cable used to be too small, causing overload during operation, and after long-term use, the heating and heat dissipation of the cable will be unbalanced, resulting in heating.

When the cables are installed too densely, the ventilation and heat dissipation effect is not good, or the cables are too close to other heat sources, which affects the normal heat dissipation of the cables, and may also cause the cables to generate heat during operation.

The joint manufacturing technology is not good, and the crimping is not tight, resulting in excessive contact resistance at the joint, which will also cause the cable to generate heat.

The interphase insulation performance of the cable is not good, resulting in a small insulation resistance, and it will also generate heat during operation.

The partial sheath of the armored cable is damaged, and the insulation performance will be slowly damaged after entering the water, resulting in a gradual decrease in the insulation resistance, and it will also cause heat generation during the operation of the cable.

After the cable generates heat, if the cause is not found and the fault is eliminated in time, the insulation thermal breakdown will occur after the cable continues to be powered on continuously. It will cause phase-to-phase short-circuit tripping of the cable, which may cause a serious fire.