• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2000-2006
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• 2011

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. Where calculation method of protection settings and Logic for Protection of Generator Asynchronization will be recommended, A distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, Zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection this paper describes an improved backup protection coordination scheme using a new Logic that will be suggested.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1006-1008
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• 1997

This paper presents the logic based High Impedance Fault(HIF) detection rules for distribution lines. Due to the characteristics of HIF, which shows low current on relaying points, it is difficult to detect the fault occurred in distribution line by the conventional overcurrent relay(OCR) and/or harmonics relay. The HIF data were generated by using TACS in EMTP. In this paper, The harmonic index is defined as the ratio of harmonic component to fundamental component. The proposed HIF detection rules are obtained by analysing the difference between normal condition and HIF condition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.5
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• pp.71-79
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• 2015

Recently, new Low Voltage DC (LVDC) power distribution systems have been constantly researched as uses of DC in end-user equipment are increased. As in conventional AC distribution system, High Impedance Fault (HIF) which may cause a failure of protective relay can occur in LVDC distribution system as well. It, however, is hard to be detected since change in magnitude of current due to the fault is too small to detect the fault by the protective relay using overcurrent element. In order to solve the problem, this paper presents an algorithm for detecting HIF using accumulated energy in LVDC distribution system. Wavelet Singular Value Decomposition (WSVD) is used to extract abnormal high frequency components from fault current and accumulated energy of high frequency components is considered as the element to detect the fault. LVDC distribution system including AC/DC and DC/DC converter is modeled to verify the proposed algorithm using ElectroMagnetic Transient Program (EMTP) software. Simulation results considering various conditions show that the proposed algorithm can be utilized to effectively detect HIF.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1542-1547
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• 2012

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. When calculation method of protection settings and logic for protection of generator asynchronization will be recommended, a distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection, this paper describes an improved backup protection coordination scheme using a new logic that will be suggested.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.43-46
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• 1991

When a fault is occurred in Power System, relay system detect overcurrent or voltage drop and trip the circuit breaker. Then, an operator in the control room diagnoses the fault and start the recovery of the system after analyzing the alarm information of relays or circuit breakers. The alarm informations have different patterns for each fault of the electric equipments on lines in power systems. In this paper, Back propagation algorithm is applied to train for many kinds of the fault in the power system. The simulation results show the possibility of the neural network application for the fault diagnosis in the case of errorous operation as well as normal operation of relays or circuit breakers.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.12
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• pp.1492-1497
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• 1999

High impedance fault(HIF) is defined as fault the general overcurrent relay can not detect or interrupt. Especially when HIF occur in residential areas, energized high voltage conductor results in fire hazard, equipment damage or personal threat. This paper proposes the model of the high impedance fault in transmission line using the ZnO arrester and resistance to be implemented within EMTP. The performance of the proposed model is tested on a typical 154[kV] korean transmission line system under various fault conditions. Wavelet transform is efficient and useful for the detection of high impedance fault in power system, because it uses variable windows according to frequency. In this paper, HIF detection method using wavelet transform can distinguish HIF form similar fault like arcfurance load, capacitor bank switching and line switching.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.754-755
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• 2011

본 논문은 발전기보호를 위한 전압억제 과전류계전기에 관한 것이다. 발전기 후비보호를 담당하는 전압억제 과전류 계전기능은 발전기 전부하전류의 150~200[%]의 범위내 과부하상태에서 불필요하게 Trip 되는 것을 방지하는 역할을 한다. 본 논문은 대형 발전기 내부사고 보호를 위한 다기능 IED 시제품 기술 개발 과제의 1차년도 진도보고의 일부로서 0사의 DGP를 Target 계전기로 삼아 연구를 수행하였다. 본 논문에서는 전압억제 과전류의 동작특성과 특성방정식계전기, 정정기준 분석 및 제시안, 논리를 알아본 후 최종적으로 알고리즘을 정립하였다.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.137_138
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• 2009

The increasing of fault current by introducing of the distributed generation(DG) in distribution system disrupts the protective coordination. Therefore, this paper applies the superconducting fault current limiter(SFCL) to solve this problem. The distribution system with DG and SFCL is modeled by EMTP. According to various size of the DG, the fault is simulated and the operating time of overcurrent relay is investigated accoring to the resistance of SFCL.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.209_210
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• 2009

계전기는 1930년대에 처음 개발되어 지금까지 수많은 발전을 거치며 전력계통의 과도현상을 효과적으로 차단해왔다. 이러한 계전기의 종류에는 많은 종류가 있으며 본 논문에서는 배전선로 보호에 주로 쓰이는 재폐로부 과전류계전기에 대한 연구를 수행하였다. 배전계통에 사용하는 과전류계전기는 이상전류가 발생할 경우 순시특성과 한시 특성을 이용하여 계통을 차단하지만 고장검출시간은 비교적 짧은 편이다. 이런 현상은 짧은 시간 안에 발생하는 이상전류에 대해서도 계통을 정전상태로 만들기 때문에 효율적이지 못하다. 따라서 이러한 문제점을 해결하고자 재폐로부 과전류계전기가 개발되어 재폐로의 특징을 이용해 좀 더 긴 고장검출 시간을 확보하여 계통의 불필요한 정전을 방지하고 있다. 본 연구에서는 재폐로부 과전류계전기를 EMTP를 이용하여 모델링하고 계전기 동작을 검증하였으며 또한 EMTP를 이용하여 모델링된 배전계통에 적용시켜 모의결과를 분석하였다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.8
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• pp.369-373
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• 2000

High impedance fault(HIF) is defined as a fault that the general overcurrent relay can not detect or interrupt. Especially when HIF occurs in residential areas, energized high voltage conductor results in fire hazard, equipment damage or personal threat. This paper proposes a fault location estimation algorithm for high impedance fault using wavelet transform. The algorithm is based on the wavelet analysis of the fault voltage and current signals. The performance of the proposed algorithm is tested on a typical 154kV korean transmission line system under various fault conditions. From the tests presented in this paper it can be concluded that a fault location estimation algorithm using wavelet transform can precisely calculate the fault point for HIF.