CASA Project overview

1. CASA-1000 HVDC
Project
OVERVIEW
ON
OPERATION & MAINTENANCE (
Part 1)
1

2. Today’s Agenda
2
1. Introduction of Participants
2. Brief on the Training Program
3. PPT Presentation on Part 1 of O
& M
4. Questions & Answers

3. INDEX
3
1. Overview of HVDC System
2. Types of HVDC system
3. HVDC system Operation
Principle
4. Major subsystems of HVDC
Syste
m
5. Control & Protection

4. 1. OVERVIEW OF HVDC
SYSTEM
4

5. Long Distance Power Transmission
a) EHV /UHV AC Systems
132/220/345/400/500/765/1000/1200
kV
5

6. Long Distance Power Transmission
b) HVDC Transmission System
± 100-450, 500/600/800/1100 kV Systems
The HVDC system uses DC for power transmission over a long
distance. HVDC transmission system is classified into the
following functional blocks as shown in Figure below;
.
• Converter transformer to step up the AC voltage • Converter
station for AC to DC conversion (rectifier) • DC Transmission
lines • Converter station to convert (overhead or underground)
back DC to AC (inverter) • Converter Transformer to stepdown the
AC voltage 6

7. Advantages of HVDC System
7
• Bulk power transmission over long distance
• Asynchronous connection (enables to
connect two electrical networks having
different frequency & voltage)
• Controlled power - DC power exchange between two
systems can be exactly determined by system
operator
• Lower line losses compared to AC line
• Economical for longer transmission systems
• Transmission at reduced voltage possible under fog
conditions
• HVDC provides stability in GRID at the time of network
fault.
• Direction of power flow can be changed
• Does not increase the short circuit level

8. ROW for Long Distance Power
Transmission System
8

9. ROW for Long Distance Power Transmission
System
9
EHV
AC
Voltag
e
Lev
el in
kV
HVDC
ROW
in M
Transfe
r
Intensit
y
MW/M
500 52 50
800 69 87
1100 85 130
Voltage Level in kV
EHV
AC
ROW in M Transfer Intensity
MW/M
132 27 3
220 35 4
400 52 10
500 60 16
765 64 35
1000/1200kV 92 85

10. Long Distance Power Transmission
Comparison
Breakeven distance-
HVDC is more
economical
 > 600 – 800 km for
overhead lines
 > 50 km for undersea
cables 10

11. 2.TYPES OF HVDC
SYSTEM
11

12. Types of HVDC System
12

13. Line Commutated Converters
13

14. Self Commutated
Converters
14

15. What is a
Thyristor ?
• A thyristor is a four-layer semiconductor device, consisting of alternating P-type
and N-type materials (PNPN). A thyristor usually has three electrodes:an anode,
a cathode and a gate, also known as a control electrode.
15

16. What is a Thyristor ?
16
• The most common type of thyristor is the silicon-
controlled rectifier (SCR). When the cathode is
negatively charged relative to the anode, no current
flows until a pulse is applied to the gate. Then, the
SCR conducts current until the voltage between the
cathode and anode is reversed or reduced below a
certain threshold or holding value. Using this type
of thyristor, large amounts of power can be
switched or controlled using a small triggering
current or voltage.

17. Thyristors vs. transistors
• Transistors need an electrical pulse to signal
the device to conduct current. Their primary
mode is a waiting state in between on and off.
Transistors also need their base signal to be
continuously refreshed to conduct current.
17

18. IGBT
Insulated Gate Bipolar
Transistor
The Insulated Gate Bipolar Transistor( IGBT) is
combination of conventional Bipolar Junction
Transistor, (BJT) and a Field Effect Transistor,
(MOSFET) making it ideal as a semiconductor
switching device in VSC
18

19. • By contrast, thyristors can be fully off or fully on. Once
a signal enters the thyristor gate and activates the
device, it remains open until a current reverse occurs
or the voltage drops below a specific level.
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THYRISTORS ARE THE BUILDING BLOCK OF
HVDC SYSTEM

20. Thyristor/Diode half wave
Rectifi
er
20

21. Thyristor Turn on Principle
21

22. Six Pulse Converters
22

23. Six Pulse Converters
23

24. Six Pulse Converters
24

25. 6 Pulse Converter /Rectifier
25

26. 6 Pulse Converter /Rectifier
26

27. 12 pulse Converter
27

28. 12 Pulse Converter /Rectifier
28

29. 12 Pulse
Converters
29

30. Types of HVDC
Systems
Back to Back
HVDC
Coupling of grids
of different
frequencies
Bipole HVDC (Point to
point)
Transmission of bulk
power over long
distance
Multi Terminal
HVDC
Pooling/Delivery of
bulk power from/to
multiple
generation/load
centres
VSC
HVDC
Black start
capability
30

31. Back to Back HVDC
31

32. Monopolar
HVD
C
32

33. Bipole HVDC
33

34. Multipolar HVDC
34

35. Bipole HVDC with DMR
35

36. QUESTIONS AND
ANSWERS
36

37. THANK
YOU
37