Gyu-Jung Cho

A Novel Reclosing Algorithm Considering Turbine-Generator Shaft Torque

Various factors exist that cause torsional interaction, such as subsynchronous resonance and switching effects following electrical disturbances. In particular, successive circuit-breaker operation may amplify the turbine-generator shaft torque under unsuccessful reclosing conditions. Thus, in this paper, we carried out transient stability analysis using the integral square error method and derived the relationship between the shaft torque amplitude and reclosing time through analysis of a 2-degree of freedom system under reclosing into permanent fault condition. In addition, we proposed a novel reclosing algorithm with consideration of transient stability and shaft torque amplitude. The performance of the proposed reclosing method was verified in actual 154 kV and 345 kV Korean study systems using the Electromagnetic Transient Program.

Analysis of Secondary Arc Extinction Effects according to the Application of Shunt Reactor and High Speed Grounding Switches in Transmission Systems

When secondary arc is caused by single phase tripping, arc should be extinguished prior to high speed reclosing which can make the system restore. In this paper, we analyzes secondary arc extinction by applying two methods that are shunt reactor and High Speed Grounding Switches (HSGS). To verify the effects of these methods in arc extinction aspects, two factors are discussed. One is secondary arc extinction time, and another is recovery voltage. Especially, secondary arc waveform and amplitude value are analyzed to identify the effects of arc extinction methods. Simulation is conducted by using ElectroMagnetic Transient Program (EMTP) based on actual Korea 765kV transmission system.

Calculation Method of Modification Factors for Fault Location Algorithm Using Boosting Current of Operating Electric Train in AT Feeding System

In general, a fault locator is installed in Sub-Station of AT(Auto-transformer) feeding system to estimate the fault location and to protect the Korean AT feeding system. Since the line impedance characteristic is different to normal 3-phase transmission line, we need particular modification factors, which can be calculated using fault location recording data, to estimate the accurate fault location. Up to recently, forcible ground test has been used to calculate the modification factors of the fault locator. However, large amount of current is occurred when the forcible ground test is performed, and this current affects to adjacent equipments. Therefore, we proposed a novel calculation method of modification factors, arbitrary trip test, using boosting current of the operating electric train. Through several field test, we confirmed that modification factors for fault locator can be easily calculated by using proposed method. Moreover, we verified the accuracy and stability of the proposed calculation method.

The Analysis of Trolley-Rail Short Circuit Current in a Single Track AT Feeding System

Abstract - In general, AT(Auto-transformer) is used to improve voltage sag and inductive interference in power lines and communication lines in AC electrical railway feeding system. Especially, Korean AT feeding system has different composition compared to other countries like Japan or France, so that it has some special characteristics. However, relays imported from other countries have been used in Korea, and settings of these relays should be modified and reflect distinct characteristics of Korean AT feeding system. Therefore, study about fault analysis based on modeled AT feeding system is important. In this paper, we modeled a single track AT feeding system by using PSCAD and analyzed fault current flow in case of trolley-rail short circuit fault. Finally, we presented current magnitude of each branch expressed by boosting current of AT.Key Words : AT Feeding System, Fault Current Analysis, Inductive Method, PSCAD†Corresponding Author : College of Information and Communication Engineering, Sungkyunkwan University, KoreaE-mail : hmwkim@hanmail.net* College of Information and Communication Engineering, Sungkyunkwan University, Korea** KOREA RAILOAD, KoreaReceived : July 3, 2015; Accepted : November 17, 2015