Power cable
An electrical lead is an object or system for transporting electrical energy and signal transmission in the network-based communications and the network-based high-frequency technology. It is part of an electric circuit or electric network, and connects the power source and load. For the transport of electrons flow as a conductor. For low transport losses, the conductive material should have a high electrical conductivity, including some metals are particularly suitable. The cross-sectional area of the conductor must take account of the permissible current density.
Description
Electrical cables consist of electrical conductors, usually in the form of wires or strands, but also of bands or bars of copper or aluminum, as well as usually their insulating sheath. Are plurality of mutually insulated conductors together, they are called line.
Sub cable is generally understood insulated electric conductors or cables with additional protective sheaths which are permanently installed and can be laid in earth and water. The cable sheath, which together existing enclosure protects the cable inside so the individual wires, from the surrounding medium, such as soil, salt water or air. A single sheathed with an insulating conductors within a cable is called a vein.
Lines, in which the ambient air serves as an insulator, hot overhead lines. They are fixed at the support points of isolators.
The term electrical line is also quite common for a low conducting deliberate connection between electrical components, and it did not arrive on the design. Size, material and design are determined by the requirements to be met for voltage, current and frequency as well as the environmental conditions faced by the management, as well as the technology.
The electrical properties of an electrical line described by the unit length, the wave impedance and dielectric strength. The cross-sectional area influences the line resistance and the heat depending on the current density. Other important characteristics of an electric line, the permissible values for the minimum bending radius, the maximum tensile strength and the heat resistance of insulating materials.
There are basically two cables for fixed installation and wiring for the connection of portable equipment. In the flexible cables or conductors are always designed as a strand. Other requirements concern of conductor ( solid or stranded, fine, extra fine ), number of cores, cross-sectional area of insulation and sheath material. For cables for fixed installation, a distinction is single core wiring cables ( plastic core cables, jumper wires, bell wire, busbars ), ribbon cables (side by side down insulated conductors with a web of plastic or rubber) and sheathed cables. The core insulation, as well as the sheath material is often made of PVC or rubber (such as SBR, CR). For flexible cables, there are twin pipes, rubber hose pipes, plastic hose pipes and silicone wire cords.
Further lines in electrical cables, pipes for alarm and signal systems, as well as cables for data networks can be distinguished.
Applications
Electric Power Transmission
Lines for the transmission even at high electric capacity power lines in the form of overhead lines or cables. For overhead lines, the conductors are also called cable ( stranded conductor, OPGW ) and fixed by means of special suspension on insulators. Overhead lines are overhead lines for the supply of electric vehicles on a current collector. The technical design of high voltage transmission lines usually three-phase lines are used. Alternatively, there is DC transmission lines and lines for single phase, the latter especially for low voltage and for traction current lines.
For power supply of stationary consumer high electrical power at low voltage (e.g., electrolysis) busbars are used. You can get great currents lead (typical value for continuous current 100 ... 3000 A, at DC to > 10000 A ) and are manufactured with a rectangular cross-section 12 × 2 mm 2 to 200 × 10 mm2, rarely with circular cross section. Faced with the problem of the dissipation of the Joule heat the rails are not isolated. Flexible cables for tougher operating conditions are current bands.
Another meaning of the term power rail for power supply of electrically powered rail vehicles and other mobile power consumers an alternative to the overhead line.
The lossless energy transfer with superconducting power cable is still in the trial. The world's longest cable of about 1 km in length is laid in 2013 in the city of Essen. His current density can be hundreds of times greater than copper; the current can be five times greater than comparable copper cables.
Signal transmission
In communications, the term line is more generally involved in a signal transduction pathway does not need may consist of an electrical conductor in the proper sense. A typical example of a cable for signal transmission is the subscriber line, is physically located mostly within telephone cables. One not only exemplary electrical line is, however, such as the telephone cable or a network cable.
High -frequency lines
Because of the behavior of the electric current at high frequencies have lines or cables for such applications a special structure. Examples are coaxial, stripline, Litz, slotted cable and waveguide and other waveguides. As a rule, no any termination resistors may be used in order to avoid mismatch with unwanted effects such as reflections. At low power levels, is usually chosen power adjustment, which, however, the efficiency is limited to 50 %.