AC systems are more common than high-voltage DC systems in the production, transmission, distribution, and use of electrical energy, although HVDC systems are more acceptable in the following cases. Below is an application of the HVDC scheme:
Applications of HVDC scheme
1. The HVDC method is more effective for high-power transport over long-distance overhead lines. So transmission is done in the HVDC method.
2. HVDC transmission is done on medium and long high power, submarine, and underground cables.
3. This method is used in back-to-back HVDC coupling stations for system interconnection.
4. Multi-terminal (MT) HVDC systems are used in AC interconnection systems with three or more phases.
5. This method is effective in cases where frequency 60Hz to 50 Hz or 50Hz to 25Hz is required, i.e. in case of change of frequency value.
Some important HVDC schemes
Below is a description of the important HVDC schemes: –
1. LCC Station in Chicago:- It consists of several wind power plants. The AC power obtained from this wind power plant is converted to 500KV through HVDC Bipdar Transmission. It is then converted to AC via Line-Commutated Converter and supplied to AC Grid. Its length is 1000 miles and the supplied power ranges from 300 to 500 MW.
2. India Bangladesh Power Transmission Line:- Recently, the largest power transmission line in South Asia has been established between India and Bangladesh. Its length is 71 km from India (Baharampur) to Bangladesh (Veramara). Which is connected to the national grid of 500 MW power from India to Bangladesh through HVDC back-to-back Asynchronous link. In this case, the 400KV Voltage of the HVDC transmission line is converted to 230KV AC and connected to National Grid Line Khulna.
3. Swedish Mainland and the Island of Scotland HVDC Scheme:- This is the world’s first commercial HVDC scheme established by submarine cable. It was established in 1953. Mercury is best used as a converting device. Whose rating is 50KV, 200A. The capacity of each unit is 20 MW, 100 KV. Using 11 valves, its capacity has been improved to 6400 MW.
4. Nelson River HVDC Scheme:- It is located in Canada. It is known as Nelson River Bipole. It uses the world’s largest mercury valve. Whose rating is 155KV, 1800 / 2000A. Its total Scheme capacity is 1620 / 1800MW at ± 450k V
5. Eel River HVDC Scheme Canada:- It is also located in Canada, it was established in 1972. This is a type of thyristor scheme. Which is connected via the Back-to-Back link. The total capacity of this plant is 31000 MW using 30 such schemes. The maximum capacity of each scheme is 320 MW.