Fig. ‘ Fault control with a fault-current limiter
Types of Superconductor SFCL types includes o Resistive SFCL, oInductive shielded core SFCL.
Resistive SFCL• Superconductor connected in series with the line to be protected.• 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.• The behavior of resistive fault current limiter is largely determined by the length of the superconductor and the type of material used for it.
Fault-Current Limiter ApplicationsFault-current limiters can be applied in a number of distribution or transmission areasThree main applications areas are• Fault-current limiter in the main position. The fault-current limiter FCL protects the entire bus• Fault-current limiter in the feeder position. The fault- current limiter FCL protects an individual circuit on the bus. Underrated equipment can be selectively protected as needed in this manner.• Fault-current limiter in the bus-tie position. The two buses are tied, yet a faulted bus receives the full fault current of only one transformer.
Fault-current limiter in the main position.The fault-current limiter FCL protects the entire bus.The most direct application of a fault-current limiter is in the main position on a bus (Fig. ).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• I2 Rt damage to the transformer is limited
Fault-current limiter in the feeder position.• The fault-current limiter FCL protects an individual circuit on the bus. Underrated equipment can be selectively protected as needed in this manner.• An FCL can also be used to protect individual loads on the bus (Fig.). The selective application of small and less expensive limiters can be used to protect old or overstressed equipment that is difficult to replace, such as underground cables or
Fault-current limiter in the bus-tie position. The two buses are tied, yet a faulted bus receives the full fault current of only one transformer. An FCL can be used in the bus-tie position (Fig. ). Such a limiter would require only a small load 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
Benefits In comparison to conventional technology, HTS fault current limiters 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
Conclusion• Electric power disruptions cause hundreds of millions of dollars worth of economic loss every year to the world’s leading economies. Worldwide energy demand is increasing rapidly, requiring new solutions to dramatically improve the reliability of our energy supply.• Fault Current Limiters are new devices, using the unique electrical properties of HTS to almost instantaneously protect power grids against short circuits and thereby prevent costly outages. They are a key member of a family of ultra-fast HTS devices and