Fault Current Limiter
Gurjeet Singh MalhiMaster 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
• Consequences of faulty operation1. 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)
Introduction
Current Limiter Approaches• Resonant Circuit Limiters
• Switched Devices
Tuned impedance Current Limiter (fig.1)
• In line fuse devices
• Superconducting devices
Silver Sand fuse FCL (fig.2)
...contd Superconducting Devices
Fig(3)Fig(4)
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 currentBelow Ilinek : Low impedance →Small voltage drop
Over Ilinek : High Impedance → Large Voltage Drop → Current Limit
- I Characteristics of FCL
Design Parameter of FCL
maxc mH l NI
To avoid loss of current limiting action and demagnetization of PM
Where Hc is coercive force of PMlm is length of PMIMax is maximum current allowed during faultUnder normal operation the voltage drop across the FCL is given by
•The voltage across the FCL during fault is given by
2(2 ) 4NOR s s sV X I fL I fL I
Contd..2 ( )FAULT u s uV X I f L L I
Design Parameter of FCL• Ratio of normal drop to supply voltage is given by.
• k = Ifault/Inor
1801u
s rs
L
L
10 15 20 25 30 35 40 45 504
6
8
10
12
14
16
18
20
Saturated permeability (relative)
Lu/L
s
For higher value of Lu/Ls, low value ofSaturated permeability, rs
System voltage up to 600v and current up to few hundreds of amperes.
supply
21 1 2 1
1
NOR s NOR s s
uu FAULT u s u
s
V X I X LLV X I k X k L L kL
Fabricated FCL
Experimental Results
Circuit with FCL
Under shorted diode condition
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
FCL with high negative current
FEM. Model of FCL during Fault
Thermal Model of FCL
Variation of Temperature with Time (Transient)
Variation of temperature with current (Steady State)
280
290
300
310
320
330
340
350
0 20 40 60 80 100Current(A)
Tem
pera
ture
(K)
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 OperationPower at Buses
Bus2_P
• BusP_3• BusQ_4
0 1 2 3 4 51.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
time (s)
0 1 2 3 4 50.85
0.85
0.85
0.85
0.85
0.85
time (s)
0 1 2 3 4 50.0647
0.0647
0.0647
0.0647
0.0647
0.0647
0.0647
0.0647
0.0647
0.0647
time (s)
Normal OperationPower flow• P7-P8
P5-P7
• P2-P7
• Q7-Q80 1 2 3 4 50.8863
0.8863
0.8863
0.8863
0.8863
0.8863
0.8863
time (s)
0 1 2 3 4 5-0.727
-0.727
-0.727
-0.727
-0.727
-0.727
-0.727
-0.727
-0.727
-0.727
-0.727
time (s)
0 1 2 3 4 51.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
1.63
time (s)
0 1 2 3 4 50.0286
0.0286
0.0286
0.0286
0.0286
0.0286
0.0286
0.0286
0.0286
time (s)
Q7-Q5
0 1 2 3 4 5-0.2287
-0.2287
-0.2287
-0.2287
-0.2287
-0.2287
-0.2287
-0.2287
time (s)
Q7-Q2
0 1 2 3 4 50.2001
0.2001
0.2001
0.2001
0.2001
0.2001
0.2001
time (s)
During Fault» BusP_1 • BusP_3
• BusP_2 • BusQ_4
0 2 4 6 8 100.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
time (s)
0 2 4 6 8 10
0.8
1
1.2
1.4
1.6
1.8
2
2.2
time (s)
0 2 4 6 8 100.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
time (s)
0 2 4 6 8 10-0.5
0
0.5
1
1.5
2
2.5
time (s)
During fault• P_5,7,8 Q_5,7,8
0 1 2 3 4 5 6 7 8 9 10-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0 1 2 3 4 5 6 7 8 9 100
0.2
0.4
0.6
0.8
1
1.2
1.4
Investigating the Optimum location of HTSFCL
• Current During Fault at different Buses
00.5
11.5
22.5
33.5
44.5
0.75 1
1.25 1.5
1.75 2
2.25 2.5
2.75 3
3.25 3.5
3.75 4
Cu
rren
t(p
u)
Time(s)
Current at Different Buses
Bus1
Bus2
Bus3
Bus4
Bus5
Bus7
Bus8
Investigating the Optimum location of HTSFCL
Investigating the Optimum location of HTSFCL
Increase in impedance
0
0.5
1
1.5
2
2.5
0.5…
0.8…
1.0…
1.3…
1.5…
1.8…
2.0…
2.3…
2.5…
2.8…
3.0…
3.3…
3.5…
3.8…
Currentat different buses
Bus1
Bus2
Bus5
bus7
Bus8
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