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Are power lines DC or AC?
Transmission lines mostly use high-voltage AC (alternating current), but an important class of transmission line uses high voltage direct current. The voltage level is changed with transformers, stepping up the voltage for transmission, then reducing voltage for local distribution and then use by customers.
What are the advantages of DC transmission over AC transmission?
1) There is no inductance, capacitance, phase displacement and surge problem in DC transmission. 2) Due to the absence of inductance, the voltage drop in DC transmission is less than the AC transmission for the same load and receiving end voltage. Because of this DC transmission has better voltage regulation.
What kind of converter is used for DC power transmission?
Currently, converter used for HVDC and UHV DC power transmission generally comprise thyristor-based converter bridges and converter transformers that supply the commutation voltage. Thyristor is a technically proven power electronic device that can withstand high voltage and has high through-current capability.
Why are AC and DC power transmission systems used?
The possibility of voltage transformation from one level to another made AC systems favorable for long-distance energy transmission. That was the main reason for them surpassing DC energy systems. Nowadays, DC systems are used in some specific applications, such as telecommunication systems, vehicles, ships, and high-voltage transmission.
What makes a DC transmission line DC transmission?
The major technical hurdle of DC transmission is that of converting alternating current to DC and vice versa so that the transmission line can interface with existing power grids. Currently, this is handled with circuits called rectifiers and inverters, which use a high-voltage triggered diode called a thyristor.
Why are lapped cables used for DC transmission?
DC transmission is used for long lengths. Use of DC is rapidly increasing following the evolution of power electronics and typologies of AC-DC converters. Different cable system solutions are available for DC applications. For bulk power transmission, lapped cables still prove to be popular because of the capacity to work up to 800 kV DC.