03-05-2012, 10:29 AM
HVDC Transmission Line
“Abstract”
HVDC Transmission Line
A high-voltage, direct current (HVDC) electrical power Transmission system uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current.High voltage is used for electric power transmission to reduce the energy lost in the resistance of the wires. For a given quantity of power transmitted and size of conductor, doubling the voltage will deliver the same power at only half the current. Since the power lost as heat in the wires is proportional to the square of the current, but does not depend in any major way on the voltage delivered by the power line. The advantage of HVDC is the ability to transmit large amounts of power over long distances with lower capital costs and with lower losses than AC. Depending on voltage level and construction details, losses are quoted.
The disadvantages of HVDC are in conversion, switching, control, availability and maintenance.The most common configuration of an HVDC link is two inverter/rectifier stations connected by an overhead power line. This is also a configuration commonly used in connecting unsynchronised grids, in long-haul power transmission, and in undersea cables. Corona discharge is the creation of ions in a fluid by the presence of a strong electric field. Electrons are torn from neutral air, and either the positive ions or the electrons are attracted to the conductor, while the charged particles drift. This effect can cause considerable power loss, create audible and radio-frequency interference, generate toxic compounds such as oxides of nitrogen and ozone, and bring forth arcing.