• 전기학회논문지
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• 제58권8호
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• pp.1512-1518
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• 2009

Recently, new dispersed power sources such as photovoltaics, wind power, fuel cell etc. are energetically interconnected and operated in the distribution systems, as one of the national projects for alternative energy. This paper deals with the optimal countermeasures for the mal-function of protective devices at primary feeder in distribution systems when new power sources like photovoltaic (PV) systems are interconnected, based on the symmetrical components of short circuit studies. When new power sources are considered to be interconnected to distribution systems, bi-directional power flow and interconnection transformer connection of new power sources may cause the operation problems of protective devices (mainly re-closer), since new power sources can change typical characteristics of distribution systems. Therefore, this paper shows an analysis skill of the mal-functional mechanism of protective relay and proposes the optimal solution for the mal-function problem using the symmetrical components of fault analysis. And, this paper also shows the effectiveness of proposed method by the simulation at the field distribution systems.

• 대한전기학회논문지:전력기술부문A
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• 제55권7호
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• pp.297-305
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• 2006

This paper summarizes a development of visualization software for protective engineering in low-voltage power systems. The study is concentrated on the following aspects. First, a software engineering method is applied for designing the object-oriented program. The design and implementation of a Graphic User Interface(GUI) and its integration to a power system framework are developed using object-oriented programming(OOP) in Visual C++. Second, we develop the short circuit analysis module that oriented a low-voltage power system. It is possible to calculate a peak, symmetrical RMS, DC component and asymmetrical fault currents for each time. And it is the first software that can calculate the fault current for single branch of three-phase system. The calculation accuracy is compared with commercial software, and the libraries of low-voltage components are served for convenience use. Third, protective engineering functions are equipped. It is possible to automatically select the circuit breaker which based on the user input characteristics and the fault current calculation and examine the protective coordination. Through the case study, we verified that the developed software can be effectively used to examine the protective engineering in low-voltage power systems.

• 전기학회논문지
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• 제57권6호
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• pp.944-950
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• 2008

When small cogenerators are operated in connected with power system, there are many positive aspects such as the reduction of power plant construction, making a improvement of power security etc. At the same time, there are some negative effects or difficulties such as we should make sure of protective coordination, especially, Actually these are not fault, but it is likely to consider the current as the fault. This is one of major causes of malfunctions for protective relays in power distribution system which is including interconnection point. Thus, in this paper, We showed that the directional protection is necessary to the dispersed generation system which is including connection point. We also executed contingency analysis to find out the magnitude of fault current and direction which are classified by fault points, length of line and kinds of faults using ETAP power system analysis program.

• 대한전기학회논문지
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• 제39권2호
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• pp.119-132
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• 1990

To design protection coordination for an electric power distribution system, an expert system is developed, using both the veteran expert's heuristics and the guide book for the distribution facility operation considering feeder configuration, service route, load characteristics fault current and load current. The expert system developed in this papaer determines the type of protective device(clearing current and sequence). The location and rating change of protective device in the old feeder is realized by using old database. Current(T-C) curves of various kinds of protective devices are stored in Knowledge Base (KB). The expert system is developed on a 32 bit personal computer using PROLOG, AutoCAD,dBASEIIIPLUS and FORTRAN. To compute the fault current and loadflow, FORTRAN is used.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.338-341
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• 2003

This paper proposes the adaptive relaying algorithm of protective devices applied in the neighboring distribution feeders for reliable and efficient operations of a wind farm interconnected with distribution networks by dedicated lines. Generally, it would be highly possible that the wind turbine generators are influenced by abnormal grid conditions such as disturbances occurring in the neighboring distribution feeders as well as the dedicated power line. The delayed operation time of protective devices for satisfying the coordination might overly expose the interconnected wind turbine generators to the fault and cause damage to them. In order to reduce the damages on the interconnected wind farm about the faults happening in distribution networks, this paper describes the proper delayed operation time of protective relay.

• 한국시뮬레이션학회논문지
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• 제22권1호
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• pp.1-8
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• 2013

신재생에너지원의 확대 보급 정책과 신재생에너지 공급 의무화 제도(RPS)의 도입으로 배전계통에 연계되는 분산전원이 증가되고 있다. 분산전원이 연계된 배전계통에서는 고장전류의 크기와 방향이 변화하게 되며, 이러한 고장전류의 변화는 기존 보호협조 체계에 대한 재검토를 요구한다. 전력연구원에서는 이러한 고장전류의 변화를 고려할 수 있는 보호협조 정정 알고리즘을 탑재한 시뮬레이션 프로그램을 개발하였다. 본 논문에서는 분산전원 연계 전, 후의 고장전류 변화를 분석하고, 시뮬레이션 프로그램을 이용하여 샘플 계통에 대한 보호협조 정정을 수행하였으며, 분산전원이 배전계통의 보호협조에 미치는 영향에 대하여 고찰하고 그 대책에 대하여 논하고자 한다.

• 한국산학기술학회논문지
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• 제14권6호
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• pp.2971-2978
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• 2013

최근 배전계통은 정부의 녹색성장 정책으로 태양광, 풍력발전 등과 같은 분산전원의 보급률이 지속적으로 증가되고 있는 실정이다. 이러한 분산전원의 연계로 기존 배전계통의 조류흐름은 단방향(One-direction)에서 양방향(Bi-direction)으로 변화되고, 고장전류의 증 감이 발생하는 등, 다양한 변화가 생겨 배전계통의 운용상에 여러 가지 문제점들이 발생할 가능성이 커지고 있다. 따라서 본 논문에서는 분산전원의 배전계통 연계에 따른 보호기기의 정정 및 양방향 보호협조 검토가 가능한 보호협조 평가알고리즘과 실제의 사고전류 값을 이용한 개선된 T-C곡선 알고리즘을 제안하고, 이 알고리즘을 바탕으로 양방향 보호협조 평가시스템을 개선하였다. 또한 평가시스템을 이용하여 배전계통을 모델링하고, 분산전원 연계 시 보호기기들 간의 보호협조를 검토하여, 분산전원이 연계된 경우 배전계통에 발생할 수 있는 기술적인 문제점들을 분석하여 그 방안을 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 하계학술대회 논문집
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• pp.129-132
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• 1990

This paper reports an expert system for coordination of protective relays in the high voltage transmission system. The proposed system consists of five modules and has adopted the frame and production rule representations achieving the efficient data storage and knowledgebases. It has an interface to the fault program PSS/E and has reduced the data retrival time by implementing the local database containg only the minimum information for the process. Different relay parameters and output formats of the setting results can be easily incorporated owing to the rule-based structure. Graphics-based output helps understanding of the process and enhances the practical power.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.932-934
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• 1998

Electric power distribution feeders are susceptible to faults caused by a variety of situations such as adverse weather conditions, tree contacts, equipment failure, accidents, etc. Distribution circuit faults result in a number of problems related to the reliability of service and customer power quality. In the past, the permanent interruption of customer service resulting from a blown fuse or a recloser lockout was the only factor which was used to determine service reliability. So we developed KODAS(Korea Distribution Automation System) with successful and had fieid-testing of Distribution Automation System in last three years at Kang-dong Branch Office. In performing the project, KEPRI has gained valuable experience, through dealing with many difficult problem. This paper is depicted about the circuit breaker coordination problems in the Underground for the Distribution Automation Feeder.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.771-773
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• 1996

This paper reports the protection coordination program, INPROSET for the industrial power system to determine the optimal TAP and Time-Dial of OCRs. INPROSET performs two stages process and the first stage starts form the highest level and depending on its results, the second stage achieves the higher relay operating time. The developed system proved effective through the tests on the real systems.