• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.283-286
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• 2003

The electric traction load is quite differ from general power system load which is single-phase, high-speed heavy load receiving power from 3-phase power system and also has variable load characteristics over time and space. Therefore, there are inevitably power quality problems such as steady state or transient voltage drop, voltage imbalance and harmonic distortion. In addition, it is expected that transient voltage sag could affect the safety of feeding system. Thus, in this paper transient analysis and voltage sag compensation of AT(Auto Transformer) feeding system are studied. The fault study of traction network is analysed by using PSCAD/SMTDC simulation tool. In addition, application of DVR in electric traction system is proposed to compensate the voltage sag of traction network which is occurred by the fault of utility source. The results of fault study will be a useful research works for operation and setting of electric traction relay. Also, it can be shown that application of the DVR in electric system is very useful to compensate the voltage sag from the result of related simulated work. The results of study will be a useful research works for management and planning of power quality in electric traction system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.8
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• pp.329-333
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• 2006

We investigated the quench characteristics of a flux-lock type superconducting fault current limiter (SFCL) depending on the number of the serial connection between the superconducting elements at the subtractive polarity winding of a transformer. The flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil through an iron core, and the secondary coil is connected to the superconducting elements in series. The operation of the flux-lock type SFCL can be divided into the subtractive and the additive polarity windings depending on the winding directions between the primary and secondary coils. In this paper, the analyses of voltage, current, and resistance of superconducting elements in serial connection were performed to increase the power capacity of flux-lock type SFCL. The power burden was reduced through the simultaneous quenching between the superconducting elements. This enabled the flux-lock type SFCL to be easy to increase the capacity of power system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.129-136
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• 2020

A Cut Out Switch (COS) is used for line protection and pole transformer protection in power systems. The COS used to protect the pole transformer is installed on the power side of the pole transformer to protect the electric equipment from fault currents. The COS is composed largely of a body and a fuse holder, and when the fault current is energized, the element of the fuse link in the fuse holder is melted to block the fault current. The arc generated when the COS fuse link is blown causes fire and noise, causing discomfort to residents in the surrounding area, and the arc flame can cause secondary damage to the peripheral device. In this study, a current-limiting COS fuse with improved overcurrent blocking performance rather than explosion type was developed to solve the arc and noise problems during COS operation. The overcurrent breaking performance of the current-limiting COS improves the reliability by developing a striker and COS fuse bracket. In addition, this study aimed to verify the performance of the developed current-limiting COS fuse through a test at an authorized institution.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.554-556
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• 2005

Distribution Automation System (DAS) will provide supervision and remote control of switches and reclosers such as pole pounted switches and pad-mounted switchgears on high voltage distribution line. Kepco had developed basic function such as remote monitoring, remote control, remote measuring and remote setting at first. As a next step, Kepco has been developed diverse application programs such as single line diagram drawing program, relay coordination program, feeder reconfiguration program, over load elimination program, bad data detection program, section load management program, fault processing program and so on. Kepco is examining to develop more powerful functions for special specification of foreign distribution automation system. This paper explains what is the target for overseas DAS market.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1490-1491
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• 2015

주파수 응답 분석기(Frequency Response Analyzer, FRA)는 수십 MHz 고주파수 범위까지 기기의 전달함수를 측정하여 변압기, 리액터 등과 같은 권선형 기기 내 기계적, 기하학적 변형을 진단하는 장치이다. 배전선로에 운영 중인 권선형 기기인 주상변압기는 현재 193만대(2015. 4 기준)가 현장에 설치되어 운전 중에 있다. 그러나 변압기의 상태진단은 권선저항 측정, 전압비 측정 등 기초적인 단계에 있으며 일부 PD 분석기법이 연구 중에 있다. 본 논문에서는 권선형 기기의 진단에 기 활용하고 있는 주파수 응답 분석기(FRA)의 측정원리를 바탕으로 주상 변압기에 적용하여 적용 가능성을 검토하였다.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.88-90
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• 2003

In this paper, an algorithm to compensate the distorted signals due to CT(Current Transformer) saturation is suggested. Firstly, WT(Wavelet Transform) is used to detect a start point and an end point of saturation. Filter banks which can be easily realized in real-time applications are employed in detecting CT saturation. Secondly, least-square curve fitting method is used to restore the distorted section of the secondary current. Fault simulations are performed on a power system model using EMTP(Electromagnetic Transient Program). A series of test results indicate that WT has superior detection accuracy and the proposed algorithm which shows very stable features under various levels of remanent flux is also satisfactory.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.8
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• pp.994-1001
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• 2018

In this paper, to studied about future power system construction using PSS / E-Python API. Python-based future system automatical construction methods and modeling of renewable sources. it confirmed the stability of the powert system for each renewable area by calculating the weighted short circuit ratio (WSCR) index. it calculated the short circuit ratio (SCR) and selected the transmission line linkage scenario to improve the stability of vulnerable areas. it confirmed the WSCR index improvement through the selected transmission line linkage of scenario, and analyzed the stability of the renewable power system applying the scenario. It describes Facts and Shunt devices adjustment for the load flow convergence. It describes the stable methed of the bus voltage through the transformer Ratio Tap adjustment. By performing PSS/E ASCC using the Python it was performed three-phase short circuit fault capacity analysis, it is confirmed whether excess of the fault current circuit breaker capacity. In order to contingency accident analysis, it have described the generation of one or two line list of each areas using the Python. The list is used to contingency analysis and describe the soluted of the transmission line overload through comparison before and after adding the scenario line.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.9
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• pp.87-94
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• 2007

This paper presents new criteria for DGA(Dissolved Gases Analysis) using CDF(Cumulative Distribution Function) obtained from the data from the diagnosis of transformers operated in KEPCO over a period of 16 years. Because of differences in operating environments, construction type, oil volume, and other factors, the interpretative criteria of DGA at KEPCO differs from other standards such as IEC-60599, or Rogers and Doernenburg. To suggest the most appropriate criteria, the DGA data from transformers under normal conditions as well as from developing fault transformers were collected. Using these data, this study suggests the limitative gas level of transformers under normal operating conditions and verifies the suitability of the criteria. Because the application of this new criterion to transformers at KEPCO increases the detectable ratio of incipient faults and reduces unnecessary follow-up sampling and analysis, the new criteria yields a more reliable prediction of transformer condition.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1604-1609
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• 2013

When the ground fault on the power side occurs on distribution system interconnected with distributed generations, the abnormal current is generated in the neutral conductor by the connection type and the iron core structure of transformers for the interconnection of distributed power supplies due to the unbalanced voltage of the system, and subsequently the false operation of the protective relay on the load side occurs. Herein, this paper proposes the method to correct errors in the phase current to prevent the false operation of the protective relay by applying p-q theory and presents the simulation result of the error correction algorithm using PSCAD/EMTDC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.23-28
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• 2015

Two old synchronous condensers in Jeju are being replaced by new machines to operate Jeju AC network with Haenam-Jeju HVDC system stably. Before new synchronous condensers operate on site, voltage stability analysis is conducted to verify stable operation of jeju AC network. Through impedance analysis of the synchronous machine, transformer and ac network, the equivalent circuit is constructed and the voltage drop during start-up is calculated. Then, PSS/E fault analysis is performed to acquire short-circuit capacity according to the generator operation scenarios. Voltage variation when starting synchronous condenser is simulated in PSCAD/EMTDC and satisfies the operating condition of jeju AC network and HVDC #1 system.