SUPERCONDUCTOR FAULT CURRENT LIMITER

SUPERCONDUCTORFAULT CURRENT

LIMITER(SFCL)

Contents1. What is fault current?2. Need for fault current limiter3. Characteristics of an ideal fault current

limiter4. Traditional ways to limit fault current5. New approaches using superconductors 6. How do SFCL works7. Types of SFCL8. Applications9. Benefits of SFCL10.Conclusion

What is fault current?

Fault current is any abnormal electric current that flows through a circuit during the electrical fault conditions

Fault current limiter is a device which limits the prospective fault current when a fault occurs.

Superconducting fault current limiters are used as effective way of fault current limiting.

Need for fault current limiter Increasing demand of

power and addition of more generators, transformers and large networks causes higher stress on power system.

Higher stresses results in higher probability of faults.

Characteristics of ideal fault current

limiter Have zero impedance

throughout normal operation Provides sufficiently large

impedance under fault conditions

Provides rapid detection and initiation of limiting action

Provides immediate recovery of normal operation after clearing fault

Traditional ways to limit fault current

Following methods are used to limit fault current-: Circuit breakers with ultra-high fault

current rating High impedance transformers Current limiting fuses Air core reactors Reconfiguration of system by splitting

power buses

New approach using superconductors

Superconductor

It is an element, inter-metallic alloy or compound that will conduct electricity without offering resistance below a certain temperature.

Types of superconductors

Low temperature superconductors(LTS)

High temperature superconductors(HTS)

Cont.. LTS are the substances that lose all

resistivity close to 4K, a temperature attainable only by liquid helium.

Examples of LTS - Lead and Mercury HTS are the substances that lose all

resistance below temperature mainly attainable by liquid nitrogen (70K).

Examples of HTS – YBCO, BSCCO etc.

How do SFCL work when operated below critical

parameters:○ Temperature (Tc)○ current (Ic)○ Magnetic field (Hc)○ Superconductors have virtually

zero resistance When operated above Tc, Ic, Hc,

normal state resistance is restored.

Cont.. The inherent

ability to switch from virtually zero resistance to a finite value when Ic is exceeded can be used to limit short-circuited, fault current.

T (Temperature)

J (current density)

B (magnetic field)

Superconductingproperties

NormalconductingpropertiesNormal

conductingproperties

Normalconductingproperties

fault current

limited fault current

Fault Current Clamping Mechanism

Types of Superconductor FCL

Resistive SFCL

Inductive Shielded core SFCL

Resistive FCL with protective shunt

superconductor

Operation of Resistive SFCL To keep it superconducting, it is

usually immersed in a coolant that is chilled by a refrigerator.

In case of a fault the inrush of current and magnetic field take the super conductor into the transition region, thereby the increasing resistance limits the fault current.

Inductive shielded core SFCL Device resembles a transformer with the

secondary side shunted by an HTS element

An electrical connection is made between the line and the HTS element through mutual coupling of AC coils via a magnetic field

Operation of inductive shielded Core SFCL

During a fault, increased current on the secondary causes the HTS element to quench, resulting in a voltage increase across L1 that opposes the fault current.

Applications of SFCL1) Fault-current limiter in the main position

Benefits of an FCL in this application include the following:

 a larger transformer can be used to meet increased demand on a bus without breaker upgrades

 I2Rt damage to the transformer is limited

2) Fault-current limiter in the feeder position

Benefits of an FCL in this application include the following The fault-current limiter FCL protects an

individual circuit on the bus. Underrated equipment can be selectively protected as needed in this manner

3) Fault-current limiter in the bus-tie  position

Benefits of an FCL in this application include the following 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 healthy bus

Benefits of SFCLIn comparison to conventional technology, SFCL provide – 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

SUPERCONDUCTING FAULT CURRENT LIMITER TECHNOLOGY IS A VERY MUCH COST EFFECTIVE, CLEAN, SAFE, RELIABLE METHOD OF FAULT CURRENT LIMITING. MANY RESEARCHES ARE GOING ON THIS TOPIC. IN RECENT DECADES, ALL OUR SYSTEMS WILL BE OF SUPERCONDUCTING TECHNOLOGY. IT IS ONE OF THE CONTRIBUTING COMPONENT OF SMART GRID TECHNOLOGY.

ONLY THE LIMITATION THEY ARE FACING IS THAT THEY CANNOT USE FOR HIGH VOLTAGES. RESEARCH STUDIES ARE GOING ON TO OVERCOME THIS DIFFICULTY.

Conclusion

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