An overhead power line is a structure used in electric power transmission and distribution to transmit electrical energy across long distances. It consists of one or more uninsulated electrical cables (commonly multiples of three for three-phase power) suspended by towers or poles.
Since most of the insulation is provided by the surrounding air, overhead power lines are generally the least costly method of power transmission for large quantities of electric energy.
Towers for support of the lines are made of wood either grown or laminated, steel or aluminum (either lattice structures or tubular poles), concrete, and occasionally reinforced plastics. The bare wire conductors on the line are generally made of aluminum (either plain or reinforced with steel or composite materials such as carbon and glass fiber), though some copper wires are used in medium-voltage distribution and low-voltage connections to customer premises. A major goal of overhead power line design is to maintain adequate clearance between energized conductors and the ground so as to prevent dangerous contact with the line, and to provide reliable support for the conductors, resilience to storms, ice loads, earthquakes and other potential damage causes. Today overhead lines are routinely operated at voltages exceeding 765,000 volts between conductors.
Overhead power transmission lines are classified in the electrical power industry by the range of voltages:
Low voltage (LV), less than 1000 volts, used for connection between a residential or small commercial customer and the utility.
Medium voltage (MV; distribution), between 1000 volts (1 kV) and 69 kV, used for distribution in urban and rural areas.
High voltage (HV; subtransmission less than 100 kV; subtransmission or transmission at voltages such as 115 kV and 138 kV), used for sub-transmission and transmission of bulk quantities of electric power and connection to very large consumers.
Extra high voltage (EHV; transmission) – from 345 kV, up to about 800 kV, used for long distance, very high power transmission.
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A utility pole is a column or post usually made out of wood used to support overhead power lines and various other public utilities, such as electrical cable, fiber optic cable, and related equipment such as transformers and street lights. It can be referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, telegraph pole, or telegraph post, depending on its application. A Stobie pole is a multi-purpose pole made of two steel joists held apart by a slab of concrete in the middle, generally found in South Australia.
Electric power is the rate at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. Standard prefixes apply to watts as with other SI units: thousands, millions and billions of watts are called kilowatts, megawatts and gigawatts respectively. A common misconception is that electric power is bought and sold, but actually electrical energy is bought and sold.
A transmission tower, also known as an electricity pylon or simply a pylon in British English and as a hydro tower in Canadian English, is a tall structure, usually a steel lattice tower, used to support an overhead power line. In electrical grids, they are generally used to carry high-voltage transmission lines that transport bulk electric power from generating stations to electrical substations before reaching its end consumers; utility poles are used to support lower-voltage subtransmission and distribution lines that transport power from substations to electric customers.
Le cours a pour objectif de présenter les éléments principaux relatifs à la conception et l¿exploitation des réseaux électriques de distribution (moyenne et basse tension) tout en tenant compte de la
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The reliability of new overhead electric and telecommunication lines depends principally on the quality of their support structures. These structures are generally made of wood, metal or concrete. The
The paper deals with the estimation of the expected annual number of flashovers in overhead power distribution lines due to indirect lightning strokes and aims at extending a procedure previously prop