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© ABB Group May 11, 2010 | Slide 1
Optimized AC transmission solutions with phase-shifting transformers and shunt reactors
Dietrich Bonmann, ABB Monselice Transformer Days, May 5, 2010
© ABB Group May 11, 2010 | Slide 2
Why phase-shifting transformers and shunt reactors? Components for efficient AC network operation
Phase-shifting transformers (PST) and shunt reactors are enablers for the increased use of renewable energy.
PSTs optimize the utilization and/or losses of existing transmission lines.
Shunt reactors control the balance of reactive power and the voltage profile in long transmission lines or in cable networks.
Variable shunt reactors respond to fluctuating loads.
Both belong to the portfolio of FACTS devices.
© ABB Group May 11, 2010 | Slide 3
Why phase-shifting transformers and shunt reactors? Enabling the use of renewable power sources
Transport of large amounts of electrical power over long distances will play an important role in achieving European goals for energy efficiency and for the use of renewables.
Bulk HVDC transmission will change power flow patterns in the supplied AC grids.
Increased injection of independent, often fluctuating renewable power.
Consequential AC transmission bottlenecks need to be managed. PSTs!
Permits for new transmission corridors are difficult to obtain.
Cables are likely to play a major role.
Capacitive currents and voltage profiles need to be managed. Shunt reactors!
© ABB Group May 11, 2010 | Slide 4
Power flow control with phase-shifting transformers Optimization of load sharing and transmission capacityTwo synchronous systems.
Transmision lines with different impedances e.g. overhead / cable or 400 kV / 110 kV.
P
P
PST impose an additional circulating current, thus improving the balance of power flows.The total transmission capacity increases.
L
GG
L
G
VS , φS
L
LG
L
VL , φL
Transmision angle
difference φS - φL
drives power flow with unbalanced load sharing of lines.The low impedance line is overloaded, limiting the total transmission capacity of the corridor.
P
P
© ABB Group May 11, 2010 | Slide 5
Examples for changes in load flow around Germany Interconnections between countries
Wind
Wind Coal
Nuke
Unscheduled load flows in Belgium
Congestion of North – South corridor
Congestion of East – West corridor
© ABB Group May 11, 2010 | Slide 6
Power flow control with phase shifting transformers Smaller scale applications
Additional infeed into urban network. New generation pattern.
New power flows in EHV network cause angle difference at infeedsto municipal networks.
Need to block parasitic power flow and overload due to transmission angle differences in feeding network(s).
Generator has contracts with two utilities.
Defined sharing of real power to different systems/ customers
φ1 > φ2 φ2
G GG
Cables dimensionedfor radial flow
G
© ABB Group May 11, 2010 | Slide 7
Typical applications for PSTs
Avoid transmission line overloading in normal operation
Avoid post-contingency transmission line overloads
Increase N-1 secure capacity of transmission corridors
Control unscheduled load flows
Keep load flows on contract paths
Minimize overall losses in the network
© ABB Group May 11, 2010 | Slide 9
Power flow control with phase-shifting transformers Phase shifting transformers are power flow controllers
)sin( LSLS
XVVP φφ −=
X
)sin( αφφ +−+
= LST
LS
XXVVPX XT
LS
LS
VLVS
VS -VL
I
φS - φL + α
The phase angle (equivalent to quadraturevoltage) between two systems determines the power exchange
© ABB Group May 11, 2010 | Slide 10
based on a picture from SETFO
Starting with a symmetrical three-phase system with a certain load flow A PST shall be used to control the load flowThe PST takes a fraction of the two neighbor phases voltageCombines them as a difference voltageWhich is then injected into the third phase
Technology PST Principle
V1S
V3S
V2S
V3L
V1L
V2L
© ABB Group May 11, 2010 | Slide 11
Example: TERNA Rondissone Increase N-1 secure transmission capacity
Customer need
Increase N-1 secure import capacity to Italy
ABB response
Support by preliminary PST designs for system study and specification
Support for protection and control engineering
Supply of 2 x 1630 MVA PSTs, protection and control for PST and bypass bays, integration of > 50 heritage bays into MMI
Customer benefits
Import capacity increased by approx. 1000 MW
© ABB Group May 11, 2010 | Slide 13
Example: Municipality of Ulm, Germany Force power flow onto contract path
Customer need
Maximize power supply via infeed with low transmission fee, but limit to 80 ± 0.5 MW
Suppress transfer flows through the city’s cable network
ABB response
Support with realistic PST data for system studies
Help with specification of PST and control system
Delivery of 100 MVA, 7° PST with very fine steps
Customer benefits
Transmission fees to EHV grid operator absolutely minimized
Pay-back in 18 months!
Viertelstundenwerte vom 25.11.2005 - 1.12.2005
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Zeit
© ABB Group May 11, 2010 | Slide 14
Example: Municipality of Ulm Pay-back in < 2 years, full exploitation of contract path
Viertelstundenwerte vom 25.11.2005 - 1.12.2005
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Zeit
Wirk
leis
tung
Del
lmen
sing
en in
MW
Without PSTWith PST
15 min values 25.11.2005 - 1.12.2005R
eal p
ower
flow
“Sou
th”i
n M
W
Time
© ABB Group May 11, 2010 | Slide 15
Example: Municipality of Ulm 100 MVA, 110 kV / 110 kV, +7° in 32 steps
Two active parts
Single tank
© ABB Group May 11, 2010 | Slide 16
Specifying a phase shifting transformer
Each unit is engineered to its specific purpose!
Physical size and cost depends on throughput power and angle regulation range.
Angle regulation range to be specified by load flow studies.
Angle increments, short circuit impedance to be determined from system requirements.
Protection and control of PSTs has special requirements.
It is highly recommended to contact your PST supplier early during the system specification stage!
© ABB Group May 11, 2010 | Slide 17
ABB phase-shifting transformer solutions
Center of Competence for PSTs in Bad Honnef since 2000
Wide range of experience:
100 MVA …1630 MVA
110 kV …400 kV
+ 7°…. ± 79°
Single and multiple active part designs
87 units total, 24 delivered + 7 in pipeline from Bad Honnef, 2 in pipeline in Cordoba.
Additional support can be offered for:
System studies: load flow, short circuit, insulation coordination
Preparation of specifications
Protection and control
© ABB Group May 11, 2010 | Slide 19
Variable Shunt Reactor Main features
Flexible voltage stabilization when renewable energy sources, such as Wind Power, are connected to the grid.
Reduce losses in cables and long over-head power lines.
Statnett, Kristiansand site
Proven design solutions are taken from our way of building shunt reactors and power transformers.
By adding a regulation winding to a traditional shunt reactor, a number of advantages are achieved, e.g.:
© ABB Group May 11, 2010 | Slide 20
Neutral
Phase terminal
OLT C
Proven design solutions from fixed inductance shunt reactors and power transformers
Variable shunt reactor design concept Unconventional reactor built on conventional technology
Proven gapped core reactor design.
Tap windings and on- load tap changer like in power transformers.
© ABB Group May 11, 2010 | Slide 21
Variable shunt reactor (VSR) winding concept An unconventional reactor built on conventional technology
© ABB Group May 11, 2010 | Slide 22
Apparent, real and reactive power
Apparent power at terminals of a line is P + QAll current carrying conductors are surrounded by an electric and a magnetic field.
Reactive power QPart of the apparent power is needed to build up the magnetic field around the conductor. The energy stored in the magnetic field just flows back and forth in each cycle.
The conductors also act as capacitances. Part of the apparent power is needed to charge this capacitance. The energy stored in the electric field just flows back and forth in each cycle.
Real power PAt the receiving end of the line one is mainly interested in current in phase with the voltage, for actually performing work.
Reactive power consumption
Reactive power generation
© ABB Group May 11, 2010 | Slide 23
Main Applications for Shunt Reactors Voltage stabilization during light load conditions
Cables generate more reactive power than overhead lines and need shunt reactors to keep the voltage stability in the grid.
A shunt reactor should be considered at every 10-12 km for a 230 kV cable or every 6-10 km for 400 kV cables.
Very long EHV overhead lines need shunt reactors during lightly loaded conditions.
0
5
10
15
20
25
30
115 230 345 500System Voltage (kV)
Mva
r/km Overhead Line
Cable
© ABB Group May 11, 2010 | Slide 24
Main Applications for Shunt Reactors Stability / voltage control at light loads
Reactor restores voltage to specified value
Voltage increase fromcapacitive generation
X
X
1
U
XQ
Q
Q
QX
© ABB Group May 11, 2010 | Slide 25
How we can contribute to a greener future Lower noise levels reduce disturbances in the close surrounding
75
80
85
90
95
100
1984 1989 1991 1996 1998 2000 2002
Manufacturing year
Soun
d po
wer
leve
l [dB
(A)]Measured sound
power level versus manufacturing year
Black column –
In the factory before delivery
Blue column –
On site in 2007
ABB Reactors have low sound power from the factory and that level is kept during the operational life time of the reactors. No degeneration.
© ABB Group May 11, 2010 | Slide 26
Save energy, reduce amount of equipment and provide flexible voltage stabilization.
Reduced voltage jump at switching on operation.
Coarse tuning of SVC equipment for best dynamical operation.
Reduction of number of breakers. No parallel fixed reactors.
Adjusting of seasonal related loads.
Adjusting of daily dependable loads.
Can be used as a flexible spare unit.
Flexibility for new load conditions in the network. At revisions for example.
Flexibility to move reactor to other locations.
© ABB Group May 11, 2010 | Slide 27
ABB variable shunt reactors References
15 variable shunt reactors delivered during 2004 -2010 to Europe, North America and Africa.
Example of regulating ranges:13-30 Mvar50-100 Mvar110-180 Mvar120-200 Mvar
The units delivered are designed for 225 to 420 kV
© ABB Group May 11, 2010 | Slide 28
Summary
Market drivers
Increased investments in renewable energy sources.
Increased energy trade and grid interconnections
Increased replacement and new deployment of cables instead of over-head lines.
ABB solution
Variable shunt reactor to adjust for daily and seasonal load variations.
Shunt reactors to reduce losses in cables.
Customer benefits
Flexible voltage stabilization.
Lower grid losses.
Reliable and state of the art ABB technology
N e u t r a l
O L T C
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