Myoung-Hoo Kim

Improvement of Recloser-Fuse Operations and Coordination in a Power Distribution System With SFCL

In this paper, we describes how to coordinate between recloser and fuse in power distribution system with superconducting fault current limiters (SFCL). The recloser and fuses are the main overcurrent protective devices in power distribution system. Universally, to protect against permanent faults, fuses are installed on overhead feeder laterals and the reclosers as a backup protection against temporary faults remove many unnecessary outages. Here, the recloser is set to trip using TCC curve for a temporary fault before any of the fuses can melt. If the fault is a permanent fault, the fuse has to melt just before the last delay trip of the recloser. However, the application of a resistive SFCL in power distribution system affects the recloser-fuse operation and coordination as decreased fault currents. In case that when a permanent fault occurs, the recloser could be locked-out after the last delay trip before the fuses operate. Therefore, to solve these cases, we performed experiments which are the recloser-fuse operation and coordination in the modeled power distribution system with the SFCL. Based on the experimental verification, we improved to coordinate the recloser-fuse in power distribution system with SFCL.

A Study on the Application of SFCL on 22.9 kV Bus Tie for Parallel Operation of Power Main Transformers in a Power Distribution System

This paper analyzed the application of Superconducting Fault Current Limiter (SFCL) on 22.9 [kV] bus tie in a power distribution system. Commonly, the parallel operations of power main transformers offer a lot of merits. However, when a fault occurs in the parallel operation of power main transformer, the fault currents might exceed the interruption capacity of existing protective devices. To resolve this problem, thus, the SFCL has been studied as the fascinating device. In case that, Particularly, the SFCL could be installed to parallel operation of various power main transformers in power distribution system of the Korea Electric Power Corporation (KEPCO) on 22.9 [kV] bus tie, the effect of the resistance of SFCL could reduce the increased fault currents and meet the interruption capacity of existing protective devices by them. Therefore, we analyzed the effect of application and proposed the proper impedance of the R-type SFCL on 22.9 [kV] bus tie in a power distribution system using PSCAD/EMTDC.

Analysis on Current Limiting and Recovery Characteristics of a Trigger Type SFCL as the Composition of the Contact

We experiment to analyze on current limiting and recovery characteristics of trigger type SFCL as the composition of the contact. Generally, some superconductor of SFCL is relatively largely loaded due to limit the fault current by oneself and recovery time is affected until the fault cleared. However, in the fault, the proposal trigger type SFCL transfer the fault current to current limiting reactor(CLR) using power switch so it could reduce the recovery time and load of the superconductor. However, because of applying the additional power switches, that could generate some power loss. Therefore, to solve this problem, we proposed the composition method of the double contact for a trigger type SFCL and analyzed on current limiting and recovery characteristics for ones.

A study on Practical Impedance of Superconducting Fault Current Limiter on Bus Tie in a Power Distribution System

This paper analyzed the selection of practical impedance of Superconducting fault current limiter (SFCL) on bus tie in a power distribution system. Generally, the parallel operation of main transformer offers a number of advantages. However, when a fault occurred in the parallel operation of main transformer, the fault currents could exceed the capacity of conventional protective device and might generate protective coordination problems. To solve these problems, the SFCL has been studied as the attractive device. Especially, in power distribution system on bus tie with SFCL, the effect of the resistance of SFCL could decrease the increased fault currents and could meet the capacity of conventional protective devices by them. Also, they could solve the protective coordination problems. Therefore, we analyzed the practical impedance of SFCL on bus tie in a power distribution system using PSCAD/EMTDC.

Current Limiting Characteristics due to Application Location of a Superconducting Fault Current Limiter in a Simulated Power Distribution System

The application of a large power transformer into a power distribution system was inevitable due to the increase of power demand and distributed generation. However, the decrease of the power transformer‘s impedance causes the short-circuit current of the power distribution system to increase and thus, the higher short-circuit current exceeds the cut-off ratings of the protective devices such as a circuit breaker. To solve these problems, several countermeasures have been proposed to protect the power system effectively from the higher fault current and the superconducting fault current limiter (SFCL) has been expected to be the promising countermeasure. However, the current limiting effect of SFCL including its bus voltage drop compensation depends on SFCL`s application location in a distributed power system. In this paper, the current limiting and the bus-voltage drop compensating characteristics of the SFCL applied into a power distribution system were studied. In addition, the quench and the recovery characteristics of the SFCLs in each location of the power distribution system were compared each other.