Surge current protection using superconductor

Made byAbhishek Walter Paul

11104EN072

INTRODUCTION

Modern power system are growing fast with more generators, transformers and large network in the system. whenever a fault occurs there is a need for the protection of these system. Here we discussed the use of superconductor as protective device for surge current protection. Superconductors conduct electricity, offering zero resistance below certain temperature. We study different types of superconductor as fault current limiter and their working

BASIC DEFINITION

• A Fault Current Limiter (FCL) is a device which limits the prospective fault current when a fault occurs (eg in a power transmission network).

• The term is generally applied to superconducting devices, whereas non-superconducting devices (such as simple inductors or variable resistors) are typically termed Fault Current Controllers.

• For example, the ground fault circuit interrupter is commonly used in residential installations.

Fault-current limiters using high temperature superconductors

• Solution to controlling fault-current levels on utility distribution and transmission networks.

• unlike reactors or high-impedance transformers, will limit fault currents without adding impedance to the circuit during normal operation.

• Development of superconducting fault-current limiters is being pursued by several utilities and electrical manufacturers around the world, and commercial equipment is expected to be available by the turn of the century.

“THE PROBLEMS”

Other common system changes which can result in a fault current problem

• additional generation from cogenerators and independent power producers raises the fault duty throughout a system.

• old equipments become underrated through system growth; some equipment, such as transformers in underground vaults or cables, can be very expensive to replace.

• customers request parallel services that enhances the reliability of their supply but raises the fault duty.

Superconductive FCL

• Removes design constraints by presenting a varying impedance in the system which changes with operating condition.

• normally operate with low impedance and are "invisible" components in the electrical system.

• During fault, limiter inserts impedance into the circuit and limits the fault current.

• development of high temperature superconductors (HTS) enables the development of economical fault-current limiters

EXAMPLE

Think of Fault Current Limiters (FCLs) as advanced and large-scale surge protectors capable of protecting large portions of the electric power grid.

Limits and regulates the amount of current moving through transmission and distribution system under abnormal conditions.

HANDLING GROUND FAULT

TYPES OF SUPERCONDUCTIVE FCL

• The Series Resistive Limiter• simplest superconducting limiter concept• exploits the nonlinear resistance of superconductors in a direct way• in its resistive state it can also be used as a trigger coil, pushing the bulk of the

fault current through a resistor or inductor• limits the energy that must be absorbed by the superconductor

• The Inductive Limiter• a resistive limiter on a transformer secondary, with the primary in series in the

circuit.• yields a limiter suitable for high-current circuits.• Inductive Fault Current Limiters for Grid Protection • 50% reduction of fault currents • ¼ cycle reaction time • handles long duration faults and breaker reclosure attempts