Presented by:

Satabdy Jena

Reg no.:10010286

Branch: Electrical and electronics Engg

7th semester

VSSUT,BURLA

SURGE CURRENT PROTECTION USING SUPERCONDUCTING FAULT CURRENT LIMITER

CONTENTS :

PRESENT SCENARIOOPTIMUM SOLUTIONOPERATION OF SFCLTYPES OF SFCLAPPLICATIONSMANUFACTURING TECHNOLOGYINSTALLED SFCLsBENEFITSCONCLUSION

PRESENT SCENARIO OF ELECTRICAL POWER

The need for electrical power has been ever increasing due to the following causes:

• Cities becoming over populated• New gadgets • Better life style• Technological advancement• Electric transportation• Growth in electricity demand by 2.5% average per year

CONSEQUENCES:

Increase of fault levels beyond existing circuit-breaker capacities

Fault levels increasing before circuit-breaker open

Some other causes behind faults: severe weather,errant tree branches,wandering squirrels,equipment failures,metal poles.

OPTIMUM SOLUTION: SFCLSelf activatingFail safeLow maintenanceHigh impedance in fault operationLow impedance in normal operationLimits fault current before first peakTolerant to a 5 cycle fault current limiting Faults interrupted within:

100 msec( 100 kV system)

60 msec( >100 kV system)

Operational before circuit breaker reclosesEnvironmental friendly(liquid Nitrogen cooling)

RECAPITULATION :SUPERCONDUCTIVITY :

It is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occuring in certain materials when cooled below a characteristic critical temperature.It is characterized by Meissner Effect,the complete ejection of magnetic field lines from the interior of superconductor as it transitions into the superconducting state.

SURGE CURRENT :

A surge current is a sudden increase in current usually caused by a voltage imbalance.Voltage imbalance is a difference in electric potential.

OPERATION OF SFCLs :

When operated below critical parameters:

Critical temperature ,Critical current ,Critical magnetic field, superconductors have virtually zero resistance.

When operated above Tc, Ic, Hc, normal state resistance is restored.The inherent ability to “switch” from virtually zero resistance to a

finite value when Ic is exceeded can be used to limit short-circuit fault currents.

MOST COMMON TYPES OF SFCLs :

RESISTIVEINDUCTIVE: SATURATED IRONINDUCTIVE: SHIELDED

OPERATION WITH SFCL:

SERIES RESISTIVE SFCL:ADVANTAGES:Compact and simple designIntrinsically safeNo reactanceResistive limiting action

DISADVANTAGES:Hot spotsAC lossesLong recovery time

INDUTIVE SATURATED IRON:

ADVANTAGES: No quench and DC operation of Superconductor

DISADVANTAGES:Significant lossesLarge sizeInductive behaviourComplex current supply for the Superconductor winding

INDUCTIVE SHIELDED :

ADVANTAGES:No current leads

DISADVANTAGES:Significant lossesLarge size and weightInductive behaviour

APPLICATION : Fault current limiter in the main position.

Fault current limiter in the feeder position.The fault current limiter protects an individual circuit on the bus.Underrated equipment can be selectively protected .

FCL in the bus-tie position.Such a limiter would require only a small current rating but would deliver the following benefits:

Separate buses can be tied together without a large increase in the fault duty on either bus.

During a fault,a large voltage drop across the limiter maintains voltage level on the unfaulted bus.

MANUFACTURING TECHNOLOGY :There are two basic technologies for HTS leads: 1.Bulk rods of ceramic superconductor:These are made by a variety of methods and of

a number of different HTS materials but the primary objectives are to achieve a rugged ceramic structure with critical current and low-resistance connections.

Advantage:Ceramics have intrinsically low thermal

conductivity Disadvantage:Ceramic rods are susceptible to breakage

during installation

Metal matrix composite leads:They use the powder in tube technology used

for BSSCO wire to manufacture a wire or tape incorporating a low thermal conductivity metal or alloy in place of customary silver matrix.

Advantage:Metallic leads are intrinsic ruggedness,high

tolerance to thermal excursions,and very low contact resistance.

Disadvantage:Higher thermal conductivity of the composite

material.

1.2 MVA SFCL in powerplant “Lontsch” in Switzerland.

The use of SFCL was first pioneered at Boxberg in 2009 in Upper Lusatia which was developed,built and commissioned by Nexan Superconductors.

BENEFITS :

Over 100 times faster response time.10 to 20 times shorter recovery time.Time adjustable response functions.1000 times the number of full-power

protection cycles.

CONCLUSION:

Electric power disruptions cause hundreds of millions of worth of economic loss every year to the world’s leading economies. Worldwide energy demand is increasing rapidly ,requiring new solutions to drmatically improve the reliability of our energy supply. Fault current limiters are new devices using the electrical properties of HTS to almost instantaneously protect power grids against short circuits and thereby prevent costly outages.They are key member of a family of ultra-fast HTS devices and machines used for electrical power.