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Fault Current Limiter
Gurjeet Singh Malhi
Master of Engineering (ME)
Massey University, New Zealand
Outline of Presentation
•
•
•
•
•
Introduction
Operation of Fault Current Limiter (FCL)
Experimental Results
Flux distribution & Thermal Model of FCL
High Temperature Superconductor(HTS) FCL
in Power System.
• Optimum Location of HTSFCL
• Conclusion
Introduction
• Electronic & Electrical devices have wide applications
in Industry
• Electronic & Electrical circuits are sensitive
• Most important concern about an device is its safe
mode of operation
• Protection from fault or short circuit is needed
.........contd
Introduction
•
Consequences of faulty operation
1.
Can permanently damage the device, which need to
be replaced
2. Need to change the circuit configuration
3. Effects the integrity of system
And the Solution ?
•
To limit fault current using Fault current
limiter (FCL)
Current Limiter Approaches
•
Resonant Circuit Limiters
•
In line fuse devices
•
Switched Devices
•
Superconducting devices
Tuned impedance Current Limiter (fig.1)
Silver Sand fuse FCL (fig.2)
...contd
Superconducting Devices
Fig(4)
Fig(3)
Fig(5)
Fault Current Limiter
Based on
Passive Devices
Basic structure of FCL
• Consists of two cores
• Permanent Magnet
• Ferrite is used as
core material
Operating Principle of FCL
•
•
Under Normal Operation
1.
Both cores operate in
saturation
2.
Low effective impedance of
system
3.
Low voltage drop
The direction of current and
MMF in cores
Operating Principle of FCL
• During fault operation
1. Cores comes out of saturation
in alternative half cycle
2. Effective Impedance of the
system increases
3. Limits the fault current
Below Ilinek ：Low impedance →Small
voltage drop
Over Ilinek：High Impedance → Large Voltage
Drop → Current Limit
 - I Characteristics of FCL
Design Parameter of FCL
To avoid loss of current limiting action and demagnetization of PM
H c lm  NI max
Where Hc is coercive force of PM
lm is length of PM
IMax is maximum current allowed during fault
Under normal operation the voltage drop across the FCL is given by
VNOR  X s I  2(2fLs ) I  4fLs I
•The voltage across the FCL during fault is given by
VFAULT  X u I  2f ( Ls  Lu ) I
Contd..
Design Parameter of FCL
•
Ratio of normal drop to supply voltage is given by.
VNOR
X s I NOR 1 X s 1 2Ls
2 1




Vsupply X u I FAULT k X u k Ls  Lu k 1  Lu
20
• k = Ifault/Inor
Ls
18
16

For higher value of Lu/Ls, low value of
Saturated permeability, rs
System voltage up to 600v and current
up to few hundreds of amperes.
14
Lu/Ls
Lu
180
 1
Ls
 rs
12
10
8
6
4
10
15
20
25
30
35
40
Saturated permeability (relative)
45
50
Fabricated FCL
Experimental Results
Under shorted diode condition
Circuit with FCL
Output at load under shorted
condition.
Flux distribution of FCL using
Finite element modelling
FEMLAB model of FCL with no
current
Model of FCL with low current
corresponding to positive half
of the cycle
Contd..
Flux distribution of FCL using
Finite element modelling
Model of FCL with large current
corresponding to positive half of
the cycle
Model of FCL with low current
corresponding to negative half of
the cycle
Contd..
Flux distribution of FCL using Finite
element modelling
FEM. Model of FCL during Fault
FCL with high negative current
Temperature(K)
Thermal Model of FCL
350
340
330
320
310
300
290
280
0
Variation of Temperature with
Time (Transient)
20
40
Current(A)
60
80
100
Variation of temperature with
current (Steady State)
Feature of FCL
• Easy to design as its a simple structure
• Passive device current limiter for AC
usage using Inductive Method
• Relatively low cost as it composes of
core, magnet and winding
• Maintenance free as its a simple
structure
• Quick recovery time due to the usage of
magnetic characteristics only
High Temperature Superconductor
FCL In Power System
•
Depends on T, B and J
•
Jc  critical Current density
•
Tc  critical temperature
•
Normal operation
•
J < Jc, T < Tc
•
Fault
•
J > Jc, T >Tc
•
Regime 1
E (j,T) = Ec*( j / jc(T))^(T)
where (T) = max[ , ’(T) ], with
•
’(T) = log( Eo/Ec) / log[( jc (77K) / jc
(T))^(1-1/)* ( Eo / Ec)^1/(77K)]
•
Regime 2
•
E (j,T) = Eo*( Ec/Eo)^
/(77K)*jc(77K)/jc(T)*( j / jc(77K))^ 
•
Regime 3
•
E (j,T) = p(Tc)*T/Tc*j
Superconductor used for HTSFCL
• Bi2223
• YBCO
Layout of HTSFCL
V =11KV
I = 1KA
Results
Normal
Under Fault
Results
Time vs Resistance
Results with different lengths
of HTSFCL
• Length =12m
Results
• Length=14m
PSAT
Modelling In PSAT
Normal Operation
Power at Buses
Bus2_P
1.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
0
1
2
3
4
5
time (s)
•
•
BusP_3
BusQ_4
0.0647
0.85
0.0647
0.0647
0.85
0.0647
0.0647
0.85
0.0647
0.0647
0.85
0.0647
0.85
0.0647
0.0647
0.85
0
1
2
3
time (s)
4
5
0
1
2
3
time (s)
4
5
Normal Operation
•
Power flow
P7-P8
Q7-Q5
-0.2287
0.8863
-0.2287
0.8863
-0.2287
0.8863
-0.2287
-0.2287
0.8863
-0.2287
0.8863
-0.2287
0.8863
-0.2287
0.8863
0
1
2
3
4
0
•
5
time (s)
• 1.63 P2-P7
1
2
3
4
5
time (s)
Q7-Q8
0.0286
0.0286
1.63
0.0286
1.63
0.0286
1.63
1.63
0.0286
1.63
0.0286
1.63
0.0286
1.63
0.0286
1.63
0.0286
1.63
0
1
P5-P7
2
3
4
5
-0.727
0
1
2
3
4
5
4
5
time (s)
Q7-Q2
time (s)
0.2001
-0.727
0.2001
-0.727
-0.727
0.2001
-0.727
-0.727
0.2001
-0.727
0.2001
-0.727
-0.727
0.2001
-0.727
-0.727
0
1
2
3
time (s)
4
5
0.2001
0
1
2
3
time (s)
During Fault
» BusP_1
•
1.1
BusP_3
1.2
1
1.1
0.9
1
0.8
0.9
0.7
0.8
0.6
0.7
0.5
0.6
0.4
0.5
0.3
0.4
0.2
0.3
0.1
0
2
4
6
8
10
0.2
0
2
4
6
8
10
time (s)
time (s)
• 2.2 BusP_2
• BusQ_4
2.5
2
2
1.8
1.5
1.6
1
1.4
0.5
1.2
0
1
-0.5
0.8
0
2
4
6
time (s)
0
2
4
6
time (s)
8
10
8
10
During fault
• P_5,7,8
Q_5,7,8
1.4
0
1.2
-0.1
1
-0.2
0.8
-0.3
0.6
-0.4
0.4
-0.5
0.2
-0.6
0
0
1
2
3
4
5
6
7
8
9
10
-0.7
0
1
2
3
4
5
6
7
8
9
10
Investigating the Optimum
location of HTSFCL
• Current During Fault at different Buses
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Bus1
Bus2
Bus3
Bus4
Bus5
Bus7
Time(s)
4
3.75
3.5
3.25
3
2.75
2.5
2.25
2
1.75
1.5
1.25
1
Bus8
0.75
Current(pu)
Current at Different Buses
Investigating the Optimum
location of HTSFCL
Investigating the Optimum
location of HTSFCL
Increase in impedance
Currentat different buses
2.5
2
Bus1
Bus2
1.5
Bus5
bus7
1
Bus8
0.5
3.8…
3.5…
3.3…
3.0…
2.8…
2.5…
2.3…
2.0…
1.8…
1.5…
1.3…
1.0…
0.8…
0.5…
0
Bus4
Conclusions
• Circuit analysis of FCL was performed using the magnetic
circuit method
• Flux distribution of FCL has been analyzed in FEMLAB
• Expected current limit characteristics were obtained
experimentally
• Thermal model of the FCL is obtained and analyzed
• Experimental results are close to the ideal characteristics.
Future work
• Performance improvement and optimum design procedure.
• Application to high voltage system in NZ.
Thank you