Why in News

 Researchers from Indian Institute of Technology (IIT) Kanpur have come up with an innovation that can help protect power grids against sudden, unexpected current surges.

• An innovative variation of the superconducting fault current limiter (SFCL), this smart SFCL not only shields the grid from large current surges and consequent fire accidents, it can also sense when the current surges will happen and warn the system about it.

The need for superconducting fault current limiter

• Power grids need protection from sudden surges in the current (fault current) that arise due to short-circuits, sudden overdrawing of power or excess power generated due to a falling demand. 
• These surges cause heating of the wires and perhaps melting and consequent short-circuits and fire accidents. 
• Earlier this used to be controlled by using circuit breakers, which would cut off the current in the event of a surge. These suffered from the limitation that if the response time to the current surge was too large, they would fail to be effective. 
• Also, once the circuit was broken to avert the accident, the switch had to be manually turned on once again, and this could lead to longer power cuts.

How to tackle this

• In the last decade, mainly in developed countries, a new way to tackle this situation is being explored – using superconducting fault current limiters (SFCL).
• This device uses a superconductor, which allows a dissipationless passage of current under normal circumstances, as it offers zero resistance to current flow in the superconducting state. 
• However, if the current flowing through it increases beyond a threshold value, as during a fault, its resistance increases sharply. The operation of a SFCL is very rapid and automatic. 
• Once the fault current reduces and the current flow returns to below the threshold value, the resistance of the SFCL also automatically goes down to zero,

What did the team achieve in this technology

• This sensor circuitry IIT has incorporated also serves the purpose of monitoring the current flow in the SFCL, which, in turn, can be used to detect the initial stages of the current surge during the appearance of a fault.  
• This can help the detection of a fault situation even while it is developing and therefore, before the large surge fully sets in, one can take pre-emptive action to intentionally switch the SFCL into a high resistive state and limit the increase in fault current and also divert the excess current through a lower resistance path.
• There is also another aspect of smartness to the device. All SFCLs are susceptible to internal thermal instabilities. The prototype they have developed is able to sense this too. This is an added advantage.

Related information

• A superconductor is a material that can conduct electricity or transport electrons from one atom to another with no resistance. 
• This means no heat, sound or any other form of energy would be released from the material when it has reached “critical temperature” (Tc), or the temperature at which the material becomes superconductive. 
• Another property of a superconductor is that it will exclude magnetic fields, a phenomenon called the Meissner effect.

Uses of superconductivity

• • Maglev (magnetic levitation) trains. These work because a superconductor repels a magnetic field so a magnet will float above a superconductor – this virtually eliminates the friction between the train and the track.

• Large hadron collider or particle accelerator.

• SQUIDs (Superconducting QUantum Interference Devices) are used to detect even the weakest magnetic field. They are used in mine detection equipment to help in the removal of landmines.
• Superconductors also makes electricity generation more efficient
• Very fast computing.
• Superconducting magnets have become the natural choice for any application where strong magnetic fields are needed – for magnetic resonance imaging (MRI) in hospitals, for example, or for magnetic separation of minerals in industry. 

Tp read about superconductivity at room temperature- https://officerspulse.com/first-room-temperature-superconductor/ 

 Reference:

1. https://www.thehindu.com/sci-tech/science/an-innovation-that-can-better-protect-power-grids/article37842349.ece