Application And Digital Simulation Of Superconducting Fault Current Limiter In Electric Power Systems

As electric power systems grow and become more interconnected, the fault currents levels have risen to exceed the available circuit breaker interruption ratings. Traditionally, to alleviate the cost of replacements of switchgears and buses, large resistors or series reactors have been used to limit the short circuit currents, so that the underrated switchgears can be operated safely. Unfortunately, resistors or reactors can cause power losses and voltage drop under normal operating conditions, thus weakening the system, Due to its low-loss nature in superconducting condition during non-fault operating, Superconducting fault current limiter(SFCL) offers a good solution to current limiting. In the event of a fault, SFCL inserts impedance into the circuit and limits the fault currents to safe level.The specific operation parameters of SFCL are defined. The model system is used to investigate the setting method of the specific parameters and their relations. Principles, types, and structures of SFCL are outlined, especially the principle of the SFCL with a diode bridge. PSCAD simulates the current waves of diode, superconducting coil and the load during normal/fault conditions, and establishes the mathematic model of SFCL; analysis the transient process of the SFCL with hybrid bridge because there isn't any bias voltage supply, this can make the SFCL applied in practice.In order to restrain the fault current effectively, this paper introduces the configuration and working principle of the SFCL with a diode bridge, and proposes the optimum design method of the superconducting coil for the limiter. The rector value of SFCL is calculated reasonably in the light of the require of TPCO (Tianjin Pipe Corporation) with the simulation test. It is proved that SFCL can not only restrain the fault current and the bus voltage drop, but also needn't replace the existing switchgears.