In initial stages DC used to be
employed for Generation, Transmission and distribution of electric power. First
DC 110 Volt Central Electric Station was installed by Edison in New York in the
year 1882. After Introduction of Transformer and single phase, Three Phase AC
system the situation changed, in favor of AC.
WHY HVDC: ADVANTAGES OF HVDC
For many reason such as facility of
transformation of voltage from one to another, better performance AC power
become popular and starts to use widely in all cases transmission, generation,
distribution.
But the supporter of DC did not
forget the advantage of DC transmission and extensive research has been carried
out in this field. As a result it has staged a sort of come back to the field
of electric power transmission at a high and extra high DC voltages.
The earlier DC schemes used mercury
arc converters. Extensive research has been carried out specially in
SWEDEN for development of high voltage converters. With the successful
development of high power thyristor ( 50KV, 100A) in early 1970's the HDVC
transmission has become technically and commercially viable alternative
to EHV/UHV AC transmission particularly for distance bulk power
transmission, cable transmission and system interconnection. For these application
HVDC transmission have distinct superiority over EHV AC transmission system.
And are being increasingly preferred.
HVDC transmission cannot be
substitute of AC transmission because for backbone Ac network, generation,
transmission and distribution. The choice of transmission system and
operating voltage for transmission line is made from...
- HV-AC (upto 220 KV)
- EHV-AC (between 440 KV to 765 KV)
- UHV-AC (grater than 765 KV)
- HVDC (upto 1600 KV)
SET-UP: HVDC
The first DC link was set up in 1954
between SWEDISH MINLAND and THE ISLAND OF GOTLAND. This was monopolar, 100 KV,
20 MW (megawatt) cable system making use of sea return. The England-France
cross channel DC link was set up in the year 1961. This was a bipolar, 100 KV,
160 MW, cable system over a distance of 65 Km. Since then more and more HVDC
system have been set up in the world.
HVDC setup in INDIA:
HVDC transmission also been
introduced in INDIA. 500 KV has been selected as the voltage for HVDC
transmission.
- Betwwen Rihand and Delhi 500 KV, 1500MW, 810 Km bipolar
HVDC line has already been set up. Its is also design to operate
bipolar-monopolar ground return and monopolar metallic return modes.
- Vindhyachal HVDC back to back is another HVDC system
set up in India. This back to back link is for exchange power between
Northern and Western regions. Each block of 250 MW is capable of
operating independently in either direction and can transfer power in
the range of 25-250 MW depending on the condition of the system.
- Chandrapur back to back project 2 x 250 MW
- Chandrapur Padghe bipolar system 500 KV, 1500MW, 736
Km.
- Jaipur back to back project 2 x 250 MW
- Mau back to back project 2 x 250 MW
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