1. HVDC AND LINKS
 BY:G.MOHAMMED MUSTAFA
EEE-THIRD-YEAR
DHAANISH AHMED OF COLLEGE
OF ENGG.

2. INTRODUCTION
HVDC Stands for High Voltage Direct Current and
is today a well-proven technology employed for
power transmission all over the world.
HVDC technology is used to transmit electricity
over long distances by overhead transmission
lines or submarine cables.
It is also used to interconnect separate power
systems,where traditional alternating current(AC)
connections can not be used.

3. Different Categories of HVDC Transmissions
Non-synchronous
Submarine cable
Long-distance
Overhead lines
Underground cable

4. HVDC System Configuration
HVDC links can be broadly classifield into:
Monopolar links
Bipolar links
Homopolar links

5. Monopolar Links
It uses one conductor
The return path is provided by
ground or water
Use of this system is mainly due
to cost considerations.
A Mettalic return may be used
where earth resistivity is too
high.
This configuration type is the
first step towards a bipolar link

6. Bipolar Links
Each terminal has two
converters of equal rated voltage
,connected in series on the DC
side
The junctions between the
converters is grounded
If one pole is isolated due to
fault,the other pole can operate
with ground and carry half the
rated load.

7. Homopolar Links
It has two or more conductors
all having the same
polarity,usually negative.
Since the corona effect in DC
transmission lines is less for
negative polarity,homopolar link
is usually operated with negative
polarity
The return path for such a
system is through ground.

8. Components of HVDC Transmission
Systems
Converters
Smoothing reactors
Harmonic filters
Reactive power supplies
Electrodes
DC lines
AC circuit breakers

9. Control of HVDC systems
Objectives of Control
• Efficient and stable operation .
• Maximum flexibility of power control without
compromising the safety of equipment.
• Principle of operation of various control
systems.
• Implementation and their performance during
normal and abnormal system conditions.

10. WHY TO PREFER HVDC THAN HVAC?
Long distance transmission
Five times more energy transmits than AC
Less losses(no inductance,capacitance)
Cost of transmission medium & land is low
Maintenance & operation cost is low
Intial cost is high but overall cost is low than
AC

11. HVDC Vs HVAC

12. Comparison between the prices and
losses of AC &DC Transmission

13. Advantages
Technical
 Reactive power
requirement.
 Short circuit current.
 Independent control of ac
system.
 Fast change of energy
flow.
 Greater reliability.
Economical
 DC lines and cables are
cheaper than ac lines or
cables.
 The towers of the dc lines
are narrower,simpler and
cheaper compared to the
towers of the ac lines.
 Line losses in dc lines are
lesser tha ac lines.

14. Disadvantages
The disadvantages of HVDC are in
conversion,switching and control.
Expensive inverters with limited overload
capacity.
Higher losses in static inverters at smaller
transmission distances .
The cost of the inverters may not be offset by
reductions in line construction cost and lower
line loss.

15. Conclusion
HVDC is very important issue in transmission
energy.
Problem of cascade blackout,can be reduced
by application of HVDC.
The data collected from 31 utilities says that
forced unavailability of energy due to the
converter station is 1.72percent.
The scheduled unavailability of energy is
about five percent.

16. QUERIES????

17. THANK YOU
PRESENTED BY:
G.MOHAMMEDMUSTAFA
EEE-THIRD-YEAR
DHAANISH AHMED COOLEGE OF ENGG.