04-07-2012, 02:33 PM
HVDC technology
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ABSTRACT:
In modern power systems network, it is essential to transmit power from one region to another region in order to meet the load demands. This can only possible by having Asynchronous power transmission between two regions operating at different frequency. This Asynchronous power transmission is called HVDC transmission.
Beginning with a brief historical perspective on the development of High Voltage Direct Current (HVDC) transmission systems, this paper presents an overview of the status of HVDC systems in the world today. It then reviews the underlying technology of HVDC systems, and HVDC systems from a design, construction, operation and maintenance points of view. The paper then discusses the recent developments in HVDC technologies. The paper also presents an economic and financial comparison of HVDC system with those of an AC system; and provides a brief review of reference installations of HVDC systems. The paper concludes with a brief set of guidelines for choosing HVDC systems in today’s electricity system development.
In today electricity industry, in view of the liberalization and increased effects to conserve the environment, HVDC solutions have more desirable for the following reasons:
HVDC in the new Electrical Industry:
The question is often asked to when HVDC transmission should be chosen over an AC system. In the past, conventions were that HVDC was chosen when:
Large amounts of power (>500MW) needed to be transmitted over long distance (>500km);
Transmitting power under water;
Interconnecting two AC networks in an asynchronous manner.
Historical perspective on HVDC Transmission
It has been widely documented in the history of the electricity industry, that the first commercial electricity generated was direct current (DC) electrical power. The first electricity transmission systems were also direct current systems. However, DC power at low voltage could not be transmitted over long distances, thus giving rise to high voltage alternating current (AC) electrical systems.
a) Important Milestones in the Development of HVDC technology
Hewitt’s mercury-vapour rectifier, which appeared in 1901.
Experiments with thyratrons in America and mercury valves in Europe before 1940.
First commercial HVDC transmission, Gotland 1 in Sweden in 1954.
First solid state semiconductor valves in 1970.
First microcomputer based control equipment for HVDC in 1979.
Conclusion:
India hasbeen a pioneer developer of HVDC since 1990 when the 1000 mw Rihand - Delhi line was commissioned in UP. Since then many 500 mw lines have come up. The 2000 mw Talcher - Kolar link is the biggest so far and spans four states: Orissa, Andhra Pradesh, Tamil Nadu and Karnataka. The project cost Rs.700 crores and was executed by Indians. The commissioning of the 200 MW, 200 KV National HVDC project has linked the 196 km. DC transmission line between Barsoor in Chhatisgarh and Lower Sileru in Andhra Pradesh.These facts should give us a measure of the little-known developmental works of very high calibre that are going on in India right now. We should be justly proud of this achievement
India is racing to a saturation point in electricity availability by 2012. 100,000 mw of power is planned to be added. HVDC technology will be waiting to ferry this power to all corners of India.