1. Fault Current Limiter Gurjeet Singh Malhi Master of Engineering (ME) Massey University, New Zealand

2. 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

3. 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

4. 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) Introduction

5. 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 )

6. ... contd Superconducting Devices Fig(3) Fig(4) Fig(5)

7. Fault Current Limiter Based on Passive Devices

8. Basic structure of FCL Consists of two cores Permanent Magnet Ferrite is used as core material

9. 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

10. 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 I linek ： Low impedance →Small voltage drop Over I linek ： High Impedance → Large Voltage Drop → Current Limit

11. - I Characteristics of FCL

12. Design Parameter of FCL To avoid loss of current limiting action and demagnetization of PM Where H c is coercive force of PM l m is length of PM I Max is maximum current allowed during fault Under normal operation the voltage drop across the FCL is given by The voltage across the FCL during fault is given by Contd..

13. Design Parameter of FCL Ratio of normal drop to supply voltage is given by. k = I fault /I nor 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. Fabricated FCL

15. Experimental Results Circuit with FCL Under shorted diode condition Output at load under shorted condition.

16. 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..

17. 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..

18. Flux distribution of FCL using Finite element modelling FCL with high negative current FEM. Model of FCL during Fault

19. Thermal Model of FCL Variation of Temperature with Time (Transient) Variation of temperature with current (Steady State)

20. 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

21. 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

22. Superconductor used for HTSFCL Bi2223 YBCO Layout of HTSFCL V =11KV I = 1KA

23. Results Normal Under Fault

24. Results Time vs Resistance

25. Results with different lengths of HTSFCL Length =12m

26. Results Length=14m

27. PSAT

28. Modelling In PSAT

29. Normal Operation Power at Buses Bus2_P BusP_3 BusQ_4

30. Normal Operation Power flow P7-P8 P5-P7 P2-P7 Q7-Q8 Q7-Q5 Q7-Q2

31. During Fault »BusP_1 BusP_3 BusP_2BusQ_4

32. During fault P_5,7,8 Q_5,7,8

33. Investigating the Optimum location of HTSFCL Current During Fault at different Buses

34. Investigating the Optimum location of HTSFCL

35. Increase in impedance

36. 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.

37. Thank you