• 대한전기학회논문지:전력기술부문A
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• 제54권6호
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• pp.315-322
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• 2005

In this article, 1 would like to explore the estimation method of time-varying voltage sags in large industrial systems considering the short circuit contributions of rotating machines. For the power distribution system of KEPCO(Korea Electric Power Corporation), the magnitude of initial symmetrical short circuit current is generally not changed. However, in industrial systems which contain a number of rotating machines, the magnitude of voltage sag is generally changed from the initial to the clearing time of a fault due to the decreasing contribution of rotating machines for a fault current. The time-varying characteristics of voltage sags can be calculated using a short circuit analysis that is considered the time-varying fault currents. For this, the prediction formulations of time-varying voltage sags are proposed using a foreign standard. The proposed method contains the consideration of generator and motor effects. For the test of proposed formulations, a simple system of industrial consumer is used for the comparison conventional and proposed estimation method of voltage sag characteristics.

• 대한전기학회논문지:전력기술부문A
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• 제52권12호
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• pp.705-712
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• 2003

In this paper, we propose new unified methodologies of reliability and its cost evaluation in power distribution systems. The unified method means that the proposed reliability approaches consider both conventional evaluation factor, i.e. sustained interruptions and additional ones, i.e. momentary interruptions and voltage sags. Because the three voltage quality phenomena generally originate from the outages on distribution systems, the basic and additional reliability indices are summarized considering the fault clearing mechanism. The proposed unified method is divided into the reliability evaluation for calculating the reliability indices and reliability cost evaluation for assessing the damage of customer. The analytic and probabilistic methodologies are presented for each unified reliability and its cost evaluation. The time sequential Monte Carlo technique is used for the probabilistic method. The proposed DVL(Demand Varying Load) model is added to the reliability cost evaluation substituting the average load model. The proposed methods are tested using the modified RBTS(Roy Billinton Test System) form and historical reliability data of KEPCO(Korea Electric Power Corporation) system. The daily load profile of the each customer type in domestic are gathered for the DVL model. Through the case studies, it is verified that the proposed methods can be effectively applied to the distribution systems for more detail reliability assessment than conventional approaches.

• 조명전기설비학회논문지
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• 제23권4호
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• pp.92-100
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• 2009

본 논문은 순간전압강하 추계적 평가를 위한 윈도우즈 프로그램을 소개한다. 개발된 프로그램을 통해 발전기 운전 스케줄링, 시변 사고율 및 부하 전압 민감도 특성을 고려한 순간전압강하 평가가 가능하다. 고장 계산, 취약지역계산, 순간전압강하 발생 횟수 추산 등 다양한 분석 기능들을 가지고 있으며 컴퓨터 그래픽과 애니메이션을 이용한 효과적인 데이터 시각화 기능도 제공하고 있다. 본 논문에서는 순간전압강하 평가의 개념과 발전기 스케줄링 및 시변 사고율을 고려한 순간전압강하 평가 방법에 대한 내용도 기술한다. 또한 개발된 프로그램을 이용한 사례 연구를 통해 순간전압강하 평가에 있어서의 발전기 운전 스케줄링 및 시변 사고율의 영향을 파악한다.