• 전기의세계
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• 제29권3호
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• pp.193-200
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• 1980

A new algorithm for power system stability calculations is developed which considers the nonlinear state equations of 8 state variables for each generator dynamics, expollential load models in respect to bus voltages for nonlinear loads, network equations expressed in terms of bus-injected current sources, various kinds of generator and transmission line outages, abrupt changes in loads, and operations of various kinds of portective relaying systems such as distance relaying, reclosing load shedding by under-frequency relays. In the algorithm are included efficient and reliable schemes for solving network equations by means of the Newton-Raphson iterative method and the Optimally-Ordered Triangular Factorization Technique, and simple procedures for determining fault-point negative and zero sequence impedances for unbalanced line faults. An application of the Optimally-Ordered Triangular Factorization Techniques results in remarkable savings in computing time and memory requirements.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
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• pp.200-202
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• 1999

This paper describes the optimization problem of real power rescheduling and present an algorithm based linear programming for studying the load-shedding and generation reallocation problem when a portion of the transmission system is disabled and at power flow solution cannot be obtained for the overload of some lines. And in case initial is infeasible, solution could not be converge. So this paper gives an algorithm being lie infeasible quantities within limit. The paper describes a LP-based algorithm to obtain the solution in power dispatch related to overload situations in power system and it is easily extened under various objective. The optimization procedures is based in linear programming with bounded variables and use the multi-segment curve method for a objective function and the validity of the algorithm is verified with two examples : 10-bus system and 57-bus system.

• 전기의세계
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• 제24권5호
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• pp.97-102
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• 1975

This paper describes the result of a Study for the Optimum Operating method with Spinning reserve in case of outage of large generator unit to improve the system stability and prevent the system frequency drop. This is usually done by governor free operation, so we focused our attention to the operating Char acteristics of spinning reserve. Nexy, a study was made to mesure the upper limit of Spinning reserve and when this upper limit cannot match the required power, a relationship between the amount of spinning reserve and that of the load shedding requirement was searched with regard to several system operating conditions to use it in our future system operation. By this study, the optimum system operating method was recommended for reliable operation of power system.

• 한국조명전기설비학회지:조명전기설비
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• 제9권2호
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• pp.123-123
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• 1995

본 논문은 대전원 탈락 사고시 계통의 지나친 주파수하락을 방지하기 위하여 주파수하락의 초기변화율을 근거로 하여 적정부하를 차단할 수 있도록 저주파수계전기의 합리적인 정정방법을 제시한다. 본 연구에서의 부하차단 전략은, 주파수가 59.5[Hz]에 이를 때 부하차단 제1단을 일으키고 제1,2단에의 크기가 주파수하락의 초기변화율을 근거하여 주어진 계통외란의 크기인 총 정태부하 차단량의 1/2이되도록 정정하였다. 그 결과 새로 제안한 방법이 주파수 회복특성에 있어서 종래의 방법보다 더 효과적임을 알 수 있다.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2015년도 추계학술발표대회
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• pp.214-215
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• 2015

데이터 스트림 환경에서 연속 질의를 처리하기 위한 데이터 스트림 처리 시스템이 개발되었다. 데이터 스트림 처리 시스템에서 질의를 처리하는 태스크에 과도한 데이터가 발생할 경우 일반적으로 데이터 스트림을 선별적으로 버리는 load shedding 방법을 이용하지만 이러한 방법은 처리 결과의 정확도가 저하될 수 있다. 따라서, 본 논문은 이를 해결하는 방법으로 분산 데이터 스트림 처리 시스템에서 데이터 스트림 분할을 통한 데이터 스트림 연속 처리 태스크의 병렬 처리 방법을 제시한다. 이를 위해 분산 데이터 스트림을 처리하기 위한 기준을 제시 및 데이터 분할 방법에 대해서 언급한다.

• 전기학회논문지
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• 제68권1호
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• pp.1-7
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• 2019

Due to the highly concentrated power plants integrated through the limited transmission lines in Korea, a Special Protection System(SPS) has been applied to stabilize the power systems by instantly tripping the pre-determined generators in a large-scaled power plant when a fault occurs on the drawing transmission lines. Moreover, power outputs of those generators are constrained to avoid any activation of Under Frequency Load Shedding(UFLS) even after those generators are tripped by SPS action. For this, this paper proposes a method for calculating the required capacity of Energy Storage System(ESS) expected to relieve the operating constraints to generators using its fast response for controlling power system frequency. The proposed method uses the generator acceleration energy to derive the stable condition during the SPS action. In addition, its effectiveness is verified by the case studies adopting actual SPS operations in Korean power systems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.280-281
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• 2011

Special Protection Scheme(SPS) that operates scenarios about faults beyond the normally protective action is wide system protection technology for the purpose of wide areas protection. Therefore, the SPS focuses on the improvement of the power supply capability by protecting the system rather than protecting the system equipments. Since the SPS requires emergency operation, the operation schedule is set up in advance by analyzing various scenarios. Since the SPS's action scheme uses generator tripping and is a classical method it is presently the most powerful one. However, as the setting of SPS is set to the most severe disturbance, the scheme tends to trip more generators than required to prevent fault propagation. It is highly likely that tripping generator units to prevent fault propagation would result in difficulty of system management and possibility of load shedding. Accordingly, it is desirable that generators are connected to the system within the range that ensures system stability and intelligent SPS is currently under development to solve the problem being stated. In this paper, as a part of developing the intelligent SPS, application of the fast-valving and braking resistor scheme to the generators is being proposed and analysed to reduce the number of tripped generators.

• 한국기계가공학회지
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• 제11권4호
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• pp.160-167
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• 2012

This paper is concerned with a particular fracture mechanics parameter ${\Delta}K_{th}$, known as the 'threshold stress intensity range', or 'fatigue threshold'. This threshold ${\Delta}K_{th}$ constitutes, as it were, a hinge between the notion of crack initiation and the notion of crack growth. It has often been thought that, like the endurance limit, it could be an intrinsic criterion of the material. The study was conducted on a SA-508 pressure vessel steel used in the nuclear power industry. This material exhibits a typical threshold effect in the range of the crack growth rates which were determined; that is, below approximately $da/dN=10^{-6}mm/cycle$, the slope of the da./dN versus ${\Delta}K$ curve is almost vertical. The value of ${\Delta}K_{th}$ was determined at a growth rate of $10^{-7}$ mm/cycle according to the ASTM Standard for threshold testing. The fatigue threshold values are in the range 21 $kg/mm^{3/2}$ to 12 $kg/mm^{3/2}$ depending on the stress ratio effect.

• 한국해양환경ㆍ에너지학회지
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• 제6권2호
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• pp.54-62
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• 2003

해저배관은 지반쇄굴로 인하여 일부분이 노출되어 자유경간이 형성될 수 있다. 자유경간이 형성되면 환경하중 및 와동유기진동에 의해서 안정성을 잃을 수 있다. 본 연구에서는 해저배관의 안정성을 위협하는 중요 요소인 자유경간의 정적 및 동적 경간을 결정하는 방법을 제시한다. 자유경간 해석에서는 해저배관에 작용하는 압축력 효과를 고려하였으며 토양의 종류에 따라 경계조건을 일반화시켰다. 자유경간 양단의 해저지반은 탄성기초로 간주하였으며, 이들 선형 및 회전 스프링으로 치환하여 경계조건을 일반화시켰다. 정적 및 동적 자유경간의 길이를 산정 할 수 있는 무차원화 된 곡선을 구하였다. 예제해석을 수행하여 그 적용방법을 소개하였다. 본 연구결과는 자유경간을 갖는 해저배관의 설계에 유용하게 적용될 수 있다.