Even with a wireless society, the role of power cables is actually growing in our daily life. You will find them all around you, from the cable that connects the router to the cables you find with your kitchen appliances. With increasing automation around us, power cable manufacturers will continue to play a major role.
Simply put, a power cable is used for carrying electricity. A power cable is an assembly of one or more electrical conductors. Given its wide range of usage, we find power cables in all kind of environments, from factories, homes, overhead, underwater and underground. Some are jacketed, while some are exposed. Some are rigid, while some are flexible.
How To Choose a Power Cable
There are a few important factors that decide the construction of a power cable. These are:
Every cable and its conductor have some resistance. This is inversely proportional to the diameter and directly proportional to the length of the conductor. Roughly, this means that resistance will be lower in a thicker and longer cable. As the current flows, there is also voltage drop in the cable. In a thin and long cable, this could also be a major factor in determining the overall length. Voltage drop must not exceed 2.5% of the provided voltage. This is often the deciding factor in creating the length.
This is the maximum current that a cable can carry. When a cable carries more current than it should, it can overheat. The size of the cable is again an important factor here. One must carefully consider the allowed length for the current carrying capacity.
Short Circuit Rating
We often find that the required conductor size in an installation is decided for its short-circuiting current carrying capacity instead of its sustained current carrying capacity. This is obviously important to avoid the hazards of a short circuit. The short circuit current carrying capacity is decided according to the circuit opening time during a short circuit condition. This essentially means that the cable should be able to withstand or contain thermal damage caused by a short circuit until a switching devise is used.
The function of the cable decides the construction, since the function decides almost all other criteria. Do you require to frequently moving around a cable or bending it? This would mean a cable with flexibility. You may also want high flex life. This is the amount of coiling and uncoiling a cable can withstand. For instance, a wind power plant where the cable is moved frequently, needing high flexibility.
Cable installation also determines what we need from a cable. Factors like environmental conditions, availability of maintenance personnel, installation crew and so on. In adverse environmental conditions, such as underground or when exposed to sunlight, we need cables with mechanical strength. The availability of personnel can also become a factor when it comes to installing overhead or in difficult terrain. We need flexible, lightweight cables in such situations. Power cable manufacturers also have to factor in the lack of availability of maintenance crew.
Not every cable is shielded. The decision to shield a cable or not is important for any medium voltage carrying cable. The main factors that are considered here are the insulation system, grounding of the system and its reliability. In cables that do not have any shielding, the electric field is partly in the insulation and partly in air. When dealing with high or medium voltage, this field can destroy the insulation and become a safety hazard. Shielding is therefore; highly recommended in aerial wires, damp conditions, and dry soil, when moving from conducting to non-conducting conditions, in presence of corrosives, to protect for radio interference and for personnel safety.
This is the outer jacketing of a cable and its main function is protection. Hence, its selection is based on the ambit temperature, load carried, type of installation, presence of corrosive factors and so on. Common insulation materials are PVC, XLPE and rubber. In some cases we also have colored cables and these are decided according to the function.
These are the main factors when deciding the right power cable. You must also check that the power cable manufacturer has complied with the given standards.