Fault Current Limiters
Dr. Michael “Mischa” Steurer
steurer@caps.fsu.edu
Center for Advanced Power Systems
(CAPS)
Florida State University
2000 Levy Avenue, Building A, Tallahassee, FL 32310
http://www.caps.fsu.edu/
Outlook
• What’s a short circuit?
• How does a FCL work?
• What are the
applications?
• What FCL technologies
exist?
• What are the system
integration issues?
• Where to learn more?
2
Short Circuits Are Unavoidable
3
Fault Currents
•
RSource
Breach of “voltage” V
Source
insulation causes
short circuits
• Short circuits lead
to excessively large
currents
• Protective relays
detect the large
current and trip a
circuit breaker CB
(or a fuse blows)
Fault
occurs
• Large number of
faults clear after CB
interruption (tree
Normal load
branch breaks,
current ILoad
squirrels die,
overhead
conductors part
touched)
LSource
ILoad
Circuit
Breaker
20...50
times
ILoad
IFault
RLoad
Circuit Breaker
interrupts
4
Fault Currents: Thermal Effects
Thermal energy
at fault location
tF
WF   i  v F dt
0
v F  const .  WF  i
Source: Bonneville Power Administration, USA
5
Fault Currents: Mechanical Effects
Source: http://www.gaiengineers.com/photos.htm
Mechanical force
between two wires
0 l
I1 I 2
F 
2 a
I1
I2
l
a
6
Different Types of SCFCLs
Resistive Type (Pure Resistive)
Operation Modes
Short-circuit
Limiter
Recovery
Rp
Without limiter
Current
iac
RQ
Switch
LQ
RSC=0
Load
Normal op.
Electrical Circuit
U0
iac
Time
7
Different Types of SCFCLs
Resistive Type (Pure Resistive)
Operation Modes
Short-circuit
Current
Without
limiter
Limiter
Recovery
Rp
iac
RQ
Switch
LQ
RSC>0
Load
Normal op.
Electrical Circuit
U0
iac
Time
8
Different types of SCFCLs
Resistive Type (Pure Resistive)
Operation Modes
Short-circuit
Current
Without
limiter
Limiter
Recovery
Rp
iac
RQ
Switch
LQ
RSC→0
Load
Normal op.
Electrical Circuit
U0
iac
Time
9
Why FCLs?
Compromise in Power Systems
Normal
Normal Operation:
Operation:
High
High short-circuit
short-circuit capacity
capacity
(low
(low short-circuit
short-circuit impedance)
impedance)
Fault
Fault Condition:
Condition:
Low
Low short-circuit
short-circuit capacity
capacity
(high
(high short-circuit
short-circuit impedance)
impedance)
••
••
Low
Low voltage
voltage drop
drop (high
(high power
power quality)
quality)
High
High steady-state
steady-state and
and transient
transient stability
stability
••
••
••
Low
Low system
system pertubations
pertubations
••
••
••
Low
Low thermal
thermal and
and mechanical
mechanical strain
strain
Reduced
Reduced breaker
breaker capacity
capacity
Optimal
Optimal Solution:
Solution:
FCL
FCL
Low
Low impedance
impedance during
during normal
normal operation
operation
Fast
Fast and
and effective
effective current
current limitation
limitation
Automatic
Automatic and
and fast
fast recovery
recovery
10
Measures To Limit Short-Circuit Currents
Permanent
Permanent increase
increase of
of impedance
impedance
at
at nominal
nominal and
and fault
fault conditions
conditions
Condition
Condition based
based increase
increase of
of impedance
impedance
Small
Small impedance
impedance at
at nominal
nominal load
load
fast
fast increase
increase of
of impedance
impedance at
at fault
fault
Old term:
“passive”
• Splitting into sub grids
• Introducing a
higher voltage range
• Splitting of bus bars
Old term:
“active”
• High impedance
transformers
• High voltage fuses
(< 1 kA, < 36 kV)
• Current limiting
air core reactors
• IS-limiter
(< 4 kA, < 36 kV)
• FCL circuit breakers
(< 1 kV)
Novel Concepts
• Superconductors
• Semiconductors
e.g. FACTS
• Hybrid systems
Sequential
tripping
Topological
Topological
measures
measures
Apparatus
Apparatus
measures
measures
Source: ”Survey of Fault Current Limiter (FCL) Technologies”, EPRI, Palo Alto, CA: 2005, 1010760
11
FCL Applications
1 FCL
FCL
1 Generator feeder
2
2 Power station auxiliaries
3 Network coupling
Transmission network
4,5 Busbar coupling
SC-Cable
FCL
Distribution
network
3
FCL
9
9
6 Shunting current limiting reactor
FCL
7 Transformer feeder
Distribution
network
Distribution
network
8 Busbar connection
9 Combination with other SC devices,
especially SC cables
4
FCL
10 Coupling local generating units
FCL
5
FCL
11 Closing ring circuits
10
6
FCL
FCL
7
FCL
FCL
8
11
Source
Noe, M.; Oswald, B.R., “Technical and economical benefits of
superconducting fault current limiters in power systems”, IEEE Trans.
Appl. Supercon. Vol. 9/2, June 1999, pp. 1347 –1350
12
Potential SCFCL Applications
Favorite SCFCL Applications
•
•above 145 kV
•
2%
Up to 145 kV
• 11%
up to 145 kV
•
11%
•
•
Above 145 kV
2%
up to 36 kV
87%
Up to 36 kV
87%
Source:
Fault Current Limiters
Report on the Activities of CIGRE WG 13.10
by CIGRE Working Group 13.10 (*), CIGRE Session 2004, Paris
13
DOE’s FCL initiative
June 27, 2007
DOE Provides up to $51.8
Million to Modernize the U.S.
Electric Grid System
Superconductor Research
Crucial to Improving Power
Delivery Equipment
FAULT CURRENT LIMITERS
American Superconductor - (DOE cost share: $12.7 million)
The team also includes: Nexans (France), the University of
Houston (Houston, TX), Los Alamos National Laboratory (Los
Alamos, NM), and Siemens AG (Germany).
Zenergy Power (formerly SC Power Systems) - (DOE cost
share: $11 million)
SC Power’s team includes: DOE’s Los Alamos National
Laboratory (Los Alamos, NM); Air Products and Chemicals Inc.
(Allentown, PA); Cryo-Industries of America Inc. (Manchester,
NH); Consolidated Edison Company (New York, NY); California
Edison Inc. (Rosemead, CA); Delta Star Inc. (San Carlos, CA);
and Trithor GmbH (Germany).
http://www.oe.energy.gov/fcl.htm
SuperPower Inc. - (DOE cost share: $5.8 million)
SuperPower’s team includes: Sumitomo Electric Industries Ltd.
(Osaka, Japan); Nissan Electric Co. Ltd. (Kyoto, Japan); The
BOC Group Inc. (Murray Hill, NJ); American Electric Power
(Gahanna, OH); and DOE’s Oak Ridge National Laboratory
(Oak Ridge, TN).
14
SCFCL Field Tests
ABB
World wide first field test of a SCFCL
At hydro power station Löntsch, Switzerland (1996)
Shielded core type SCFCL
Main data:
Voltage
10 kV
Current
70 A
Temperature
77 K
BSCCO2212 tubes
Scheme
Iron core
LN2
Superconductor
Copper winding
Cryostat
Courtesy ABB
15
SCFCL Field Tests
CURL10
World wide first resistive SCFCL field test
at RWE, Germany (field test April 2004-March 2005)
Demonstrator application in a 10 kV busbar coupling
110 kV
15 MVA
Sk = 125 MVA
uk = 12,5 %
Main data:
Voltage
12 kV
Current
600 A
Lim. time
60 ms
Max. current
8.75 kA
Temperature
65 K
Max. E-field
0.6 V/cm
MCP-BSCCO2212 bifilar coils
FCL
10 kV
pulsating loads
grid interference
Photo: ACCEL, Germany
16
Solid State FCL
• No cryogenics
• Immediate recovery
• Fail safe
• No current distortions
• SuperGTO
• Lower losses
• Reduced size and
weight
SGTO-based Power Processor
7’
5’
9’
• 15kV, 1200A RMS
• Power stack = 108” (w) x 60” (d) x 84” (h)
17
Saturated Iron Core FCL
RL
M
W
-V2
_0
Man
i.
12
0
Vs
V
Man
i.
MW
-V
2_0 MW
-ph2
_0
90
60
.0
12
0
0
F
RRL
Phase
Ph
-90
SHA
NDIN
15
11
-2kV
Fre
q
de
g
V
k
11
5
M
W
-p2
h_0
P==-05.3.5238
Q
95
V=120
A
V
P_
Sou
rc
e
Q_
Soruc
e
Q_
Sou
rc
e
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V
e
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V
rc
e
Tm
i ed
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L
kr
Log
ic
Co
l se
d@
t0
Tm
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L
ker
Lg
oci
Co
l sed@
t0
Tm
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8
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1[u
F]
#1
A
V
2
#3 #
2
#3 #
#1
00
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1[u
F]
2
#3 #
P=03
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Q=01
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V=10
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2
M
P
E2
34
9
0.00
1[u
F]
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L
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L
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L
Man
i.
CA
PSW
-0
0
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676M
[W
]
12
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7[M
AR]
V
RCI1
44
9
P=0
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302
Q=0.1
735
V=10
.37
CAP
SW
P=0
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317
Q=0
.6
102
V=10
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A
V
. 2M
1
[VA
R]
PM
H3
431
A
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bus107
03
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W
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[V
AR]
CAPS
W
03
.[M
W
] 01
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[VA
R]
P=03
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23
Q=01
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61
V=1
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02
P=03
.20
9
Q=0
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1
V=10
.3
2
A
V
A
V
0
COUPL
ED
PI
SE
CTION
GS
426
9
Sha
nd
i
O
18
,8
0'
70
5XL
P
.2
0
3[M
W
] 0
.6
1[M
VAR]
03
.0[M
W
]01
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VAR]
su
b2
1kV
Main
SW
C
GS
15
47
W
S
SW
GS5
13
FI15
V
44
0
SW
COUP
LED
PI
SECT
IN
O
Ia4
Ia4
Ib4
Ib4
RM
S
P=.53
53
Q=-03
.88
2
V=10
.44
A
V
in
L
e
Ava
nti
12kV
,10
20A
FCL
oad
L
41
3'
100L
XP
Ia
4_RM
S
CO
UPLED
PI
SE
CTION
PI
SECT
ION
PI
SE
CTION
64
,5
1'
100XL
P
64
,15
'
100XL
P
RM
S
,3
3
68'
100
0
XLP
A
V
J9
88
OUPLE
C
D
COUPLE
D
COU
PLED
I
P
SCTION
E
I
P
SCTION
E
PI
SEC
TION
20
,31
'
1000
XLP
20
,2
7'
100L
XP
51
,0
6'
100L
XP
P=0.356
3
Q=0.178
4
V=1.09
3
Ib4_
RMS
fau
lt
Ic4
A
V
P=47
.8
6
Q=-08
.14
1
V=.13
07
P=38
.22
Q=-1.30
3
V=10
.3
A
V
COU
PLED
PI
SE
CTION
P=.5
3
Q=1
-.43
6
V=10
.3
P=30
.1
8
Q=-1
.0
73
V=.13
03
A
V
A
V
10'
0
00X
1
0LP
CO
UPLED
COUPL
ED
PI
SE
CTION
PI
SECITN
O
90'
0
000
1
XLP
14
,8
4'
100XL
P
P=07
.2
85
Q=03
.9
86
V=.0
132
P=0
.9
311
Q=0
.9
146
V=10
.32
COUPL
ED
A
V
A
V
PI
SECTION
P=03
.91
3
Q=01
.95
1
V=.13
02
11
,9
0'
100L
XP
A
V
Ia4_
RMS
Ib
4_RM
S
Man
i.
Ic4
P=51
.3
7
Q=-0
.4
607
V=.13
07
Ic
4_RM
S
O C
Ic4
_RMS
fau
lt
P=0
Q=0
V=0
fautl
A
V
P=0.35
49
Q=0.179
1
V=1
.3
04
P=0
.9
518
Q=0
.8
291
V=10
.3
A
V
A
V
03
.6[M
W
]0.13
8[M
AR]
V
A
V
0
03
.2M
[W
] 01
.6M
[V
AR]
0.55[M
W
] 02
.7[M
VA
R]
03
.2M
[W
]0.16[M
VA
R]
Ifa2
Tm
i ed
Fau
lt
BC->G Log
A
i c Ifb2
Ifb2
Ifc2
Ifc2
RMS
RMS
P=03
.1
27
Q=01
.0
62
=10
V
.33
A
V
If2
a_RMS
Ifa2_
RM
S
.2
0
3[M
W
]0
.6
1[MV
AR]
If2
b_RMS
.0
0
3[M
W] 0
.5
1M
[ VA
R]
Ifc2
_RM
S
LOTS
P
ZPPo
l ts_
PHAS
E_AL
RMS
If2
c_RM
S
Ifc2
_RM
S
Tested@G
ridVotlage=120kVwtihreducedcircuit
M
odifiedFaultO
NR
ESS
I TAN
CE=0.01OH
M
P0
=3
.912
Q=.09
151
V=10
.3
2
A
V
40
E
219
6
P=0.1
608
Q=00
.0
81
V=10
.33
S13
B
89
CAP
SW
2
-0
0
.9
001
9[M
W
]
.1
1
98[M
VA
R]
Ma
in
CAPS
W
2
APSW
C
2
03
.66M
[W
]01
.83M
[VA
R]
O
0
1.8[M
VAR]
A
V
sw4
Ma
i n.
.5
0
1[M
W]0
.7
05[M
VAR
]
w4
s
O
PS2
06
2
36AC
SR
65
4'
36
3ACSR-M
lug
tiroud
ned
CO
UPLED
PI
SE
CTION
48'
5
100
0
XLP
P=15
.8
3
Q=1
-1
.38
V=1
.3
02
A
V
COUP
LED
PI
SEC
TION
13
,4
2'
100L
XP
RC
I15
43
P=.18
53
Q=1
-1
.3
8
V=1.032
0
A
V
w4
s
CO
UPLED
PI
SE
CTION
00'
1
100
0
XLP
P=15
.82
Q-1
=1
.3
8
V=10
.3
2
P0
=4
.047
Q=1
-7
.2
3
V=10
.3
2
A
V
A
V
P0
=3
.955
Q=.09
151
V=10
.3
2
CO
UPLED
A
V
PI
SE
CTION
20'
100L
XP
P=07
.6
85
Q=03
.9
81
V=1
.3
02
03
.7[M
W
]0.183M
[VA
R]
A
V
OUPLE
C
D
12 kV
800 A
23 kA rms
20%
30 cycles
Instantaneous
CS136
R
5
PIO
IN
SEC
T
10'
35
0XLP
Voltage:
Current:
Prospective Fault:
Fault Reduction:
Fault Duration:
Recovery Time:
S15
G
46
COUPL
ED
91'
5
100L
0
XP
Ifa2
Specifications:
GS14
55
COU
PLED
fautl
Southern California Edison, USA
Energized 9 March 2009
RM
S
0.3[M
0W
]01
.5[M
VA
R]
CS1
R
08
18
Saturated Iron Core FCL
Requirements:
Voltage:
Current:
Prospective Fault:
Fault Reduction:
Fault Duration:
Recovery Time:
American Electric Power, USA
Energization early 2012
FCL
138 kV
1300 A
20 kA rms
43%
5 cycles x 5 shots
Instantaneous
FCL – 345 kV /138 kV
Feeder application
19
Saturated Iron Core FCL
Present
Future
Benefit – replace conventional reactor with FCL
and reduce steady state voltage drop by 75%
20
Issues Around FCL Integration
• FCL characteristics introduce new system dynamics
– Validated models for system simulation studies needed
– Standard testing procedures must be developed
– System protection must be investigated
• How to coordinate FCL characteristic with existing protection
schemes?
• New protection schemes are possible with FCL for future systems
• Cryogenics (for SCFCL)
– Utilities are not used to cryo systems
– Coordination with other demonstration projects (SC-cables, SCtransformer, SC-condenser) can yield to mutual benefits
regarding acceptance
21
Impact of FCL on Protection Systems
Fault With FCL In Front of Re lay (50% Line Le ngth)
3
•
Slowing of fault clearing
governed by inverse-time
characteristics of conventional
protection schemes
• False readings of impedance
relays upstream of the FCL
location
• Effects of non-sinusoidal fault
currents
• Simplifying the sometimes
complex existing schemes which
are to overcome circuit breaker
limits
FCL in upstream of PTs and CTs
=> Distance relay does not trip
2
Trip
1
Current
0
(kA)
Relay
State
Normal
-1
Total
S upe rconductor
S hunt
trip
-2
-3
0.14
0.15
0.16
0.17
t (s )
0.18
0.19
0.2
22
FCL Working Groups
•
CIGRE brochure 239 “FAULT
CURRENT LIMITERS IN
ELECTRICAL MEDIUM AND
HIGH VOLTAGE SYSTEMS”
• CIGRE brochure 339
“GUIDELINE ON THE IMPACTS
OF FAULT CURRENT IMITING
DEVICES ON PROTECTION
SYSTEMS”
• CIGRE WG A3.23 “Application
and feasibility of Fault Current
Limiters in Power Systems”
• IEEE WG PC37.302 “Guide for
Fault Current Limiter Testing”
ramp approx
. 100 ns
ramp approx. 100 ns
23
23 kVpeak
kV peak
µs/div
11
µs/
div
6.7 6.7
kV/
div
kV/div
lightning impulse set - up
75 kV BIL test of CURL10 device
23
Concluding Remarks
• Fault Current Limiters
(FCL) are emerging Smart
Grid technologies
– Facilitate cost effective
increase in power
transmission capacitances
– Reduce impact of
disturbances
– Increase equipment life
24