• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1152-1154
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• 1999

Recently. due to the drastic development of communication method between substations for pilot protective relaying system. The power line carrier(PLC) application is getting obsolete. Consequently, the coupling capacitor voltage transformer (CCVT) loses its necessity for the carrier coupling function, and so wound voltage transformer(VT) can be used to substitute CCVT for voltage signal. However, VT has been reported to give rise to ferro-resonance phenomena, so sufficient consideration on applying the VT to line side is required. This study introduces probable technical problems in using the VT on T/L side, and carries out feasibility study on the basis of modeling results by EMTP(Electro-magnetic transient program)

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1404-1406
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• 1999

전력계통에서 전류를 측정하는 변류기는 주요 전력 설비와 연계되어 보호 및 감시에 있어 중요한 역할을 수행한다. 그러나 기존방식의 전류 변성기는 자기포화에 의한 파형 왜곡과 써지나 잡음 등의 전기적 장치가 갖는 구조적 문제점을 가지고 있다. 이러한 문제점을 개선하기 위한 방법으로 전류에 의해 형성된 자계에 의해 광신호의 편광(polarization) 회전을 발생시키는 Faraday 효과를 가지는 광센서를 이용하여 보호계전 분야에 적용 가능한 전류계측기술을 개발하였다. 본 논문에서는 기존 전류변성기의 계통 보호에서 발생하는 문제점을 PSCAD/EMTDC 시스템을 이용하여 시뮬레이션 하였으며, 아울러 동일 조건에서 광 CT의 동작 특성을 산출하여 기존 전류변성기와 비교 분석하였다. 분석 결과들로부터 광 CT는 기존 전류변성기가 자기포화되는 상황에서도 정확한 1차 전류의 측정이 가능함을 보였다.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.59-62
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• 1992

Power system fault transient signals are highly distorted due to the presence of high frequency components in the voltage and current signals and an exponentially decaying dc-offset component in the current signals. Modern protective relays have to make reliable fast decisions about the nature of a fault in the presence of such transients. To use a dc-offset removing filter makes relay algorithms much fast and reliable for detecting a fault. In this paper, several dc-offset removing filters are described, and characteristics of them are compared.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.284-290
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• 2000

The measurement of electric current using optical techniques provides a number of important practical advantages including effective isolation from high line potentials and freedom from the saturation effects observed in conventional current transformers. In this work the optical current sensor which uses thin YIG(Yittrium Ion Garnet) film as a Faraday element has been developed. We have characterized this optical current sensor and implemented it to the OOCR(Opto-electronic OverCurrent Realy) Performance of the OOCR shows the possibility of replacing the present overcurrent relays with OOCR.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.143-146
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• 1987

Fiber optics provide a solution to the problems at interference, capacity and reliability in communication. Approximately 20 kilometera of a six-fiber, multimode, longwave($1.3{\mu}m$), graded index silica glass fiber optic cable was helically wrapped around a phase conductor at a Korea Electric Power Corporation(KEPCO) 154KV transmission line. This paper presents an economic comparison of several fiber optic cable installation alternative and discusses the characteristics at the helically wrapped fiber cable, as well as the entire installation, including high voltage phase-to-ground (PTG) end termination, and splicing. The fiber link was installed for the field trial and practical use with overhead composite optical fiber cable which installation performed a few years earlier some other location and is intended to accommodate not only telephone but also supervisory Control and Data Acquisition(SCADA), protective relaying, and telemetry functions.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.463-468
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• 1987

In this paper, a high impedance fault detection on 22.9kV multigrounded distribution system that has been very difficult by any existing conventional protective relaying systems is studied. Because the fault current is very low, it cannot be distinguished from neutral current caused by load unvalanced on multigrounded distribution system. We developed the new and best algorithms of high impedance ground fault detection. This algorithms are 'the even order power method, even order ratio method', 'and even order ratio varience method'. Using this algorithms, a detection device for high impedance faults is constructed and tested in the laboratory. And continually, it is installed and has been tested in KEPCO substations.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.249-251
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• 2001

The two fuzzy criteria to distinguish the internal fault from the inrush for the power transformer protection have been identified. They are based on the terminal voltage, fundamental and second harmonic component of differential current. A systemetic way to determine the associated fuzzy membership function is also proposed.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.552-554
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• 2003

The second harmonic component is commonly used for blocking differential relay in power transformers. However, it is difficult to distinguish between inrush and internal winding fault with differential current protective relaying. This paper proposed a new method using Nuro-Fuzzy System based on HCM(Hard C-Means). The proposed system is more objective and systematic than existing model. The data used in input are 3-phase primary voltage and fundamental harmonic of differential current. Various states of transformer are simulated using BCTRAN and HYSDAT of EMTP. As a result of the application of algorithm in various cases, the exact discrimination between internal winding fault and inrush is performed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.495-496
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• 1998

The measurement of the amplitude and phase of electric fields on high voltage transmission lines is important for several reasons including a) Metering and determination of power flow, b) protective relaying. and c) fault sensing. The work reported here is directed toward a major improvement to optically based, electric-field sensors. This is a signal processing based technique for overcoming the instabilities of conventional, optically-based, electric-field sensors to changes in optical power or temperature.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.11
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• pp.655-660
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• 2003

This paper describes a transformer protective relaying algorithm based on the ratio of increments of flux linkages (RIFL) of the primary and secondary windings. The algorithm uses integration approximation. The RIFL is equal to the turns ratio for all operating conditions except for an internal fault. For a single-phase transformer and a Y-Y transformer, the increments of flux linkages (IFL) are calculated. For a Y-$\Delta$ transformer, the difference of IFL are calculated to use the line currents rather than the delta winding currents, which are unavailable. Their ratios are compared with the turns ratio. The comparative study between the proposed and conventional differentiation approximation methods was conducted. The test results show that the algorithm reduces the approximation errors of the conventional methods.