High Voltage Direct Current Transmission line is highly use in today's generation for long power transmission system because it has many great advantages over HVAC Transmission system. It's requires low transmission line space and more space we can use around transmission line over HVAC transmission line.
3. • Introduction
• Need to shift on HVDC system
• First HVDC project
• Advantages
• Disadvantages
• Interconnecting India with world through HVDC
• HVDC in India
• HVDC Links and its types
Seminar Review 1
4. What is HVDC Transmission ???
• High Voltage Direct Current
• HVDC is transmission system which transmits
energy over long distance at High Voltage and
in Direct Current through overhead
conductors or submarine cables.
5. Need to shift on HVDC system.
• HVAC systems have more electrical losses compared
to HVDC systems over long distance.
- The absence of skin effect with DC also beneficial in
reducing power losses marginally.
• To connect two systems having different frequencies
and voltage levels.
• Renewable energies like solar can be directly
transmitted to electric grid without converting it to
AC.
6. • HVAC systems are more complex to build then
HVDC systems, and HVDC systems have more
controllability.
• Distance between two conductors of AC
systems needs to be kept more, as there is flux
linkage is occurred.
7. First HVDC Projects
• First line commissioned between Västervik on
the mainland and Ygne on the island of
Gotland in 1954.
- Capacity: 20 MW at 100 kV
• First Installation in North America in 1969
- Vancouver Island
- 312MW at 260 kV, 46miles of submarine
cable
8. Advantages
• Controlled Power Exchange
• Improved Stability of power system
• More economical efficient then HVAC for long
distance transmission.
[ Cut from: Power Grid Booklet ]
9. • Costs of insulators and conductors increases in
AC transmission system, compared to HVDC
transmission system.
• The corona effect tends to be less significant
on DC conductors than for AC.
• DC line carry as much Power with 2
conductors as an AC line with 3 conductors of
the same size.
• Two systems with different values of
quantities can be easily interconnected.
10. Disadvantages
• Difficulty in breaking DC currents, which
increases costs of DC breakers, as appropriate
circuit breakers for DC are not available.
• Costly converter equipments. (i.e. AC to DC
and DC to AC)
• Costlier for short distance transmission.
14. Links??
• Links connects two networks or systems.
• For connecting two networks or systems,
various types of links are used.
15. Types of HVDC Links
I. Monopolar Link
II. Bipolar Link
III. Homopolar Link
16. Monopolar Link
• In this type, one negative conductor is used
for transmission and return path is provided
through ground or sea or metallic return. It
has many disadvantaged as it uses ground as
return path. Today there is rarely seen this
type of links.
[ Cut from: Wikipedia ]
17. Bipolar Link
• In this have two conductors; one positive and
other one is kept negative of same value with
respect to ground.
[ Cut from: Wikipedia ]
18. Homopolar Link
• It has two conductors of the same polarity
usually negative polarity, and always operates
with earth or metallic return. In the
homopolar link, poles are operated in parallel,
which reduces the insulation cost. This system
is not used presently.
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19. References
• K. R. Padiyar HVDC Power Transmission
Systems (Technology and System Interactions)
• Powergrid booklets
• Wikipedia
• ABB booklets
• SEIMENS booklets
20. • What is HVDC
• HVDC converters
ꟷ 12 pulse converter
• HVDC Inverters
ꟷ 12 pulse inverter
• Case Study on Agra to Biswanath line.
Seminar Review 2
21. What is HVDC Transmission ???
• High Voltage Direct Current
• HVDC is transmission system which transmits
energy over long distance at High Voltage and
in Direct Current through overhead
conductors or submarine cables.
22. Heart of HVDC system
• HVDC converters
• HVDC Inverters
23. HVDC Converters
• In HVDC for converting AC to DC for transmission
different types of converters are used.
• Basically in HVDC system Converters based on
controlled semiconductor devices i.e. SCRs are used.
• 12 pulse converter is most widely used converter.
26. 12 Pulse Converter
• It is used for converting AC voltage to DC at
transmitting end.
• As per name it creates 12 pulses in one full cycle of
AC.
27.
28. 12 pulse Inverter
• It converts DC voltage to AC at receiving end, as
distribution has to be done in AC.
• In inverter, output of converter will become input of
inverter and vice-versa.
29. Conductors
• In overhead transmission of HVDC normal
conductors of steel can be used.
• In underground transmission of HVDC mainly two
types of conductors are used:
-XLPE Plastic Insulation
-Oil impregnated insulation
30. XLPE Plastic insulation
• Cross Linked Poly-Ethylene
• This cable is light in weight. (10 kg/m)
• Used in voltage source converter application.
• It is flexible in nature.
• Maximum cable voltage is 320 kV.
31. Oil impregnated insulation
• Heavy weight cable.
(25 kg/m)
• Requires special
abilities and
instruments to install
it.
• Maximum cable
voltage 500 kV.
• It is proven highly
reliable till today`s
date.
• It is also known as
Single Core Mass
Impregnated.
32. Agra to Biswanath
• It is first HVDC multi terminal transmission line
installed in INDIA.
• It has capacity of 6000 MW at ±800 kV.
• It has length of 1728 km.
• It is transmitted from Agra, from hydroelectric power
station.
• And power is received at Alipurduar, west bengal.
• And it is also received at Biswanath Chariali, Assam.
33. • Agra has two bipolar converters, connected in
parallel.
• Each terminal has the capacity of 1500 MW. And
overload rating is 2000 MW.
• It has biggest advantage that if any one of the
terminal fails to supply power rest of will be in sound
condition and able to transmit power.
34.
35. References
• K. R. Padiyar, HVDC Power Transmission
Systems (Technology and System Interactions)
• Edward Wilson Kimbark, Direct Current
Transmission
• Alstom`s Booklet
• Special Report, 60 years of HVDC by ABB
36. • HVDC Circuit Breakers
• Types Of Circuit Breaker
- Electromechanical CB
- Solid State CB
• Switchgear
• Maintenance
• Major Problems faced in maintenance
• References
Seminar Review 3
37. • Circuit Breakers are most essential part in
protection circuitry in HVDC network.
• When any fault is occurred in transmission line
then for disconnecting the circuit from supply, we
are using the circuit breakers.
• Basic tasks of Circuit Breaker are:
- To interrupt the current when fault occurs
- To sustain the voltage appears across it
HVDC Circuit Breakers
42. • The changing in generation and load structure in
existing power grids requires increased
transmission capacity.
• Longer transmission distances and increased
loading tends to reduce the AC grid’s static and
dynamic stability. To amend this, HVDC systems
can be integrated into existing AC grids to provide
the required transmission capacity and at the
same time increase grid stability.
Switchgear
43.
44. Air Insulator
• Air is act as insulation
medium .
• Require four time more
space compare to GIS
Switchgear.
• Maximum rated voltage is
800 kV and max. current
is 8000 A and short circuit
current is 80 kA.
45. • GIS is used where space
is limited, for example,
extensions, in city
buildings, on roofs, on
offshore platforms,
industrial plants and
hydro power plants.
• Range of GIS is from
72.5 kV to 1200 kV.
• Its require less space
compare to AIS
Switchgear.
• Detection of fault in GIS
is easy compare to AIS.
Gas Insulator (SF6)
46. • PASS (plug and switch
system) hybrid AIS and GIS
concept provides a fully
integrated and self-contained
switchgear module which can
cut the space required for a
new substation by up to 70
per cent.
• The new PASS M0
switchgear module is a hybrid
of ABB’s traditional air
insulated (AIS) and SF6
metal-clad gas insulated (GIS)
switchgear units.
ABB launches innovative PASS M0 145kV
substation switchgear module
47.
48. In maintenance basically following processes are included:
• Checking status of thyristors
• Tightening of Nuts and Bolts
• Checking Protection Circuits
• Checking all AC equipments in switchyard
• Measuring insulation resistance of all insulators
• tanδ test of transformer oil
• Status of Buchholz relay
• Status of relays and other equipment
• Checking cooling system
Maintenance
49. • Failure of Thyristor
• Failure or degraded efficiency of cooling system
• Bugs in softwares used in testing kits
• Lower accuracy of testing kits
Common problems in Maintenance
50. 1. `Operation & Maintenance of HVDC Station`, overview
report from Powergrid Corporation Of India Ltd.
2. Website a Report from URL:
http://circuitglobe.com/hvdc-circuit-breaker.html
3. Report on HVDC Circuit Breaker by Nikolaos Kostoulas,
Vasileios Sitokonstantinou, Mohammad Idris,Patrick
Sterling, Saadman Sayed and Petros Karaiskos
4. Website: www.abb.com
5. Website: www.siemens.com
References
SCR like symbol shows converting circuit. For this 12 pulse converter unit is used, which has 12 SCRs. Due to these major disadvantage most of countries do not allow these system.
Load can be directly connected between these two wires. Both sides and for both conductors identical converting circuit is used, so return current trough ground is almost zero.
It is also commonly said as 3 wire system. It has the highest efficiency of all three link systems. It has 2 outer ire and a neutral wire. It has advantage that voltage is divided between two sets formed by three wires. For domestic load of 230 V, one neutral and one outer can be used. And for industry loads 2 outer wires can be used.
