By J DAVID MANOHAR (08A31A0232)

NECESSITY OF SUPERCONDUSTOR  Damage from short circuit is constant threat in power systems  All the power systems components must be designed to withstand over short circuit stresses  If the higher fault currents are anticipated then higher equipment required. Hence maintenance cost increases

PROPERTIES OF FAULT CURRENT LIMITER  Having zero impedance under normal operation  It provide larger impedance whenever any fault occur  It provides immediate recovery after clearing the fault  It has a capacity to addressing two faults within a period of 15 sec

 In past we are limiting fault current by artificially raising the impedance  Now such methods are inconsistence for today’s demand of high power quality  These drawbacks can be overcome by using fault current limiter

SUPERCONDUCTORS  Because of their sharp transition from zero resistance at normal operations to higher resistance in the fault condition  Super conductors having critical temperature can be maintained by liquid nitrogen

TYPES OF SCFCL  RESISTIVE SCFCL:  In RESISTIVE SCFCL the super conductor is directly connected to line to be protected  It was immersed in a coolant and it chilled by refrigerator  Current leads are design to transfer heat from outside to coolant

 SHIELDED CORE SCFCL:  The shielded core fault current limiter basically a shorted transformer  Here the superconductor is connected to the line not directly but magnetically  The primary coil is connected in series to the line to be protected and secondary side is superconducting and shorted

FAULT CURRENT LIMITER  Recently the distributed generators are introduced to the load system side  The fault current will increase with installation of DG’s  Usually a limiting reactor is set in series with DG’s  If you use SCFCL in place of reactor it reduces fault current and transmit maximum power under steady state condition

ADVANTAGES OF SCFCL OVER REACTOR  It can be decided by conducting two tests I. Current limiting test: Consider generator output and load are 3KW and 1.5 KW respectively If the peak of the fault current is 120 amps without SCFCL, it is suppressed to 46.3 amps Without SCFCL the power to the load during the fault dropped almost zero KW on other hand it was kept to some level with SCFCL

 STEADY STATE STABILITY TEST:  Consider a reactor whose impedance is same as SCFCL in current limiting mode  The steady state stability test carry out through SCFCL or reactor  The SCFCL reduce fault current without decreasing maximum power and stability margin

RESULTS  The SCFCL turns in to current limiting mode when fault current reached to triggering current  The DG is successfully from over current at the fault condition  Power supply to the load continuous to certain extent during the fault  SCFCL reduce fault current without decreasing maximum power and stability margin

SCFCL BENEFITS  Safety, reliability and power quality  Cost for circuit breaker and fuses can be reduced  Reduce voltage drops  Enhance grid stability

CONCLUSION  The purpose of this paper was the study of surge current protection using superconductors the SCFCL offers efficient advantages to power system and opens of major applications for superconducting material

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