HVDC transmission systems use direct current for the transmission of electrical power over long distances or undersea. They have advantages over AC transmission such as lower transmission losses over long distances and the ability to interconnect unsynchronized AC power systems. HVDC technology has evolved from early electromechanical systems using motor-generator sets to modern thyristor-based systems. HVDC is used for long distance bulk power transmission projects in India such as Rihand-Delhi and Chandrapur-Padghe.

1. HVDC TRANSMISSION
SYSTEM
Presented by: Sagnik Roychowdhury
3rd year
Department of Electrical Engineering
College: Future Institute Of Engineering &
Management
Class Roll No:62
University Roll No:14801610062

2. Introduction
• Beginning
• History of HVDC Transmission
• Advantages of HVDC over AC Transmission
• Disadvantages
• Costs of High Voltage DC Transmission
• Component & Diagram
• Corona Discharge
• The Future prospect
• Applications
• Conclusion
• Bibliography

3. Beginning
1. Uses direct current for transmission of electrical
power.
2. Should be used over long distance.
3. Can be used underwater.

4. Continued….
• The modern form of HVDC transmission uses
technology developed extensively in the 1930s in
Sweden at ASEA.
• Early commercial installations included one in the
Soviet Union in 1951 between Moscow and
Kashira, and a 10–20 MW system between
Gotland and Mainland Sweden in 1954.

5. High Voltage DC Transmission
• Full form of HVDC is High Voltage Direct
Current.
• Two AC systems having different frequencies
can be linked up together by means of HVDC
link.
• HVDC technology is used to transmit
electricity over long distances.

6. Why DC Transmission?
• Losses are less.
• Two conductors required.
• Less Expensive.
• Can be used over long distance.

7. History of HVDC Transmission
• Electromechanical (Thury) Systems
• Mercury Arc valves
• Thyristor Valves
• Capacitor –Commutated Converters(CCC)

8. Electromechanical (Thury) Systems
First Power transmission:
Betwwen Miesbach-Munich
Time:1882
Capacity:2.5 kW
Thury System:
• series-connected motor-generator sets used.
Moutiers-Lyon System for 8000 kW 200 km distance. René Thury
• Used eight series-connected generators with dual
commutators.
• Between 1906 to 1936
Fifteen Thury systems were in operation by 1913.

9. Mercury Arc valves
• Between 1920 to 1940
• In 1932 GE tested first mercury-vapor
valves.
• Elbe-projest in 1941.
• Fully static mercury arc valve to
commercial service in 1954.

10. Continued…
• Required an external circuit to force the current to
zero and thus turn off the valve.
• In HVDC applications, the AC power system itself
provides the means of "commutating" the current to
another valve in the converter.
• Also known as LCC.

11. Thyristor Valves
• Since 1976, new HVDC systems have used only solid-state
devices, in most cases thyristor valves.
• Thyristors require an external circuit (in HVDC applications,
the AC power system itself does this) to turn them off.
• On March 15, 1979, a thyristor based direct current
connection between Cabora Bassa and Johannesburg (1410
km, ±533 kV, 1920 MW) was turned on.

12. Capacitor –Commutated Converters(CCC)
• To overcome the limitations of LCC, CCC was introduced.
• It is conventional.
• LCC using thyristor valves, where series capacitors are inserted
into the AC line connections, either on the primary or secondary
side of the converter transformer.
• The series capacitors partially offset the “commutating
inductance” of the converter and help to reduce fault currents.
• Reducing the requirment of reactive power by allowing
‘extinction angle’ to be used at an inverter.

13. ADVANTAGES
• Occupies less space.
• Less expensive.
• Synchronization of two AC power supply.
• Does not transmit short circuit current.

14. DISADVANTAGES
• Complexity of control.
• Inability to use transformers to change voltage
levels.
• High cost of convention equipment.
• The difficulty of breaking DC current which
results in high cost of DC currents.

15. Costs of High Voltage DC Transmission
• The manufacturers do not state the exact cost
of a particular project.
• Depends on power rating, circuit length,
overhead vs. underwater route, land costs,
and AC network improvements required at
either terminal.

16. Component
• Converting transformer
• Converter bridge
• Surge arresters
• Smoothing reactors
• Filters(AC & DC)

17. Types of DC Links
Monopolar Biplolar Homopolar

18. Diagram

19. Corona Discharge
• Corona discharge is the creation of ions in a fluid
(such as air) by the presence of a strong electric field.
• Both AC and DC transmission lines can generate
coronas, in the former case in the form of oscillating
particles, in the latter a constant wind.
Pdc=P0+K(E-EC)2 kW/km

20. The Future Prospect
• Next 25 years HVDC market will be dominated by
“force commutated converter”.
• However, the force-commutated converters using
capacitive commutation never outgrew niche use,
due to the rapid emergence of the second trend
today, in favour of “self-commutated converters”
which use more complicated semiconductor
devices which can be directly turned off by gate
action.

21. Continued….
• These self-commutated devices include the insulated
gate bipolar transistors (IGBT) and variants of the
thyristor such as the integrated gate-commutated
thyristor(IGCT), and gate turn-off thyristor (GTO).
• Self-commutated converters, more commonly known
as "Voltage-Sourced Converters" started to appear in
1997 with the experimental Hellsjön–Grängesberg
project in Sweden, and by the end of 2011, this
technology had captured a significant proportion of
the HVDC market.

22. Applications
• Long distance bulk power transmission.
• Under ground or under water cables.
• Asynchronous interconnection of two AC
power supplies.

23. Application of HVDC in INDIA
• Rihand-Delhi and Chandrapur-
Padghe were the first long
distance HVDC projects in INDIA.
• In 1990 ,Rihand-Delhi (Singrauli)
thermal power complex with a
combined power generation of
several thousand MW was put in
to service. It covers over a
distance of 814km.
• In 1998,the 1500 MW
transmission Chandrapur-
Padghe was putting to service. It
covers over distance of 736 km.

24. Conclusion
• With the HVDC systems, the power flow can be controlled
rapidly and accurately as to both power level and direction.
This possibility is often used in order to improve the
performance and efficiency of connected AC networks.
• Using HVDC to inter connect two points in a power grid, in
many cases is the best economic alternative, and further
more it has excellent environmental benefits.
• The HVDC technology is used to transmit electricity over long
distances by overhead transmission lines or submarines
cables.
• HVDC overland links are usually bipolar, on overhead lines.
Compared to AC , DC transmission has several advantages.

25. Bibliography
• GOOGLE.COM
• WIKIPEDIA.COM
• A COURSE IN POWER SYSTEM
by J.B.Gupta

26. THANK YOU