HVDC systems have several benefits over traditional AC systems for long distance power transmission. HVDC allows for more efficient transmission by requiring fewer conductors and towers. It also reduces line losses, as reactive power losses are eliminated. HVDC transmission is more environmentally friendly due to lower electric and magnetic fields that do not vary over time. Radio interference is also reduced compared to AC systems. These technological and economic advantages make HVDC transmission preferable over long distances.

1. HVDC systems
(introduction and benefits)
H.soltani.g
shahid bahonar uni of kerman
(h.soltani.g.92@gmail.com)
Dec,2016

2. HVAC benefits:
AC technology was introduced as the standard for generation,
transmission and distribution of electrical energy,because:
-voltage conversion is simple
allows high power levels
- An AC transformer allows high insulation levels
within one unit
has low losses
-…

3. Introduction of HVDC system

4. • Monopolar links
• Bipolar links
• Homopolar links
HVDC links
can be broadly
classified into:
HVDC System Configurations

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.

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 (or more using overload
capabilities of its converter line).

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. HVDC Transmission Types

9. HVDC Transmission Types

10. HVDC Transmission Types

11. HVDC Benefits

12. HVDC Benefits
Economic
Aspects

13. Suitable for long distance power delivery
HVDC Benefits Economic
Aspects

14. But why it is economical in long distance transmission?
Transmitting power over DC lines requires fewer conductors
and smaller tower
HVDC Benefits
Economic
Aspects

15. An example:
HVDC Benefits Economic
Aspects

16. HVDC Benefits
Technological
Aspects

17. HVDC Benefits Technological
Aspects
-For a given cable conductor area, the line losses with
HVDC cables is about 50% of that AC cables. This is
due to carrying reactive component of
current
skin-effect
-suitable for asynchronous interconnections

18. - HVDC can carry more power per conductor

19. HVDC Benefits Technological
Aspects

20. HVDC Benefits
Environmental
Benefits

21. To recognize the benefits of HVDC let’s
compare it with conventional AC
technology
(according to paper by L. A. Koshcheev (2003) on the potential
environmental impacts of HVDC overhead transmission lines in
comparison to HVAC lines)

22. 1. Effects of Electric Fields
The electric field produced by a HVDC transmission line is a
combination of the electrostatic field created by the line voltage
and the space charge field due to the charge produced by the line’s
corona.
-The discomfort to humans that is typically felt under HVAC
transmission lines is not observed under HVDC lines.
-large machines with rubber tires (such as combine harvesters,
automobiles,…) are not electrically charged to dangerous levels
when the machines are standing under HVDC overhead lines.

23. Electric fields around HVDC line

24. 2. Effects of Magnetic Fields
-The maximum magnetic field strength of an AC power
transmission system varies from 10 to 50 μT (micro Tesla) near the
line, while exposure levels at residences, for example, are typically
less than 1 μT.
But
The magnetic fields associated with DC lines produce no
perceivable effects. The strength of the magnetic field around
HVDC transmission lines is in the same range as that of the Earth’s
natural magnetic field.
-Unlike AC magnetic fields, which continuously vary in
strength and polarity with the associated electric current, DC
magnetic fields are of relatively constant strength, orientation, and
polarity.

25. Magnetic field around HVDC line

26. 3. Radio Interference
The radio interference caused by electric power
transmission lines is the result of the corona discharge
around conductors at positive voltages.
-HVDC line radio interference is generated only by
positively charged conductors, whereas HVAC
interference is generated by all three AC phases.
-AC lines contribute up to a 10 dB (decibel) increase in
radio interference under rainy conditions, while DC
line radio interference decreases during rain.
-Radio interference levels from HVDC lines are
typically 6-8 dB lower than those of HVAC lines of
similar capacity.

27. 4.land usage
The towers of the DC lines are narrower, simpler and cheaper
compared to the towers of the AC lines.

28. AC Transmission Line

29. DC Transmission Line

33. References:
1-ENVIRONMENTAL CHARACTERISTICS OF
HVDC OVERHEAD
TRANSMISSION LINES (Prof. L. A. Koshcheev
, May, 2003)
2-www.energy.siemens.com
3-www.abb.com
4-www. electrical-engineering-portal.com
5-http://www.slideshare.net/zunaibali/dc-
transmission?qid=87715dd8-1cc1-43d4-b51f-
8cfbeaee25a9&v=&b=&from_search=1