• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 A
• /
• pp.190-192
• /
• 2002

The industrial power distribution system is a radial system and therefore usually protected with time delayed over current relays (OCR's). Proper time dial settings are provided at the OCR's. Meanwhile, the systems, where synchronous generator, or synchronous motors, or large induction motors are operating, can not be protected with only OCR's with time grading. This paper presents a technical limit and a suitable range of time delay in applying OCR's to clearing faults in the industrial power systems for maintaining stability. Dynamic simulations are made to show them employing a real power systems of a large petro-chemical complex.

• 재무관리연구
• /
• 제20권2호
• /
• pp.201-234
• /
• 2003

본고에서는 세계시장 중에서 주요 7 국가의 시장을 대상으로 시장의 이례현상의 하나인 주말 효과와 주중 일별수익률에 대한 연구를 결제청산과정으로 접근 분석하였다. 결제청산과정은 특정한 날의 일별수익률에 영향을 미칠 수 있고 또한 시장마다 서로 다른 결제청산체계는 세계 각 시장에서 특정한 날의 일별수익률에 서로 다르게 영향을 미칠 수 있다. 최근 이러한 결산청산체계 자체가 미국, 영국 프랑스 등 여러 주요시장에서 변화가 일어났다. 그리하여 본고에서는 세계 각 국가시장에서 주식의 결제청산과정체계의 변화 및 전환에 따라 주말효과 및 주중 일별수익률의 변화에 미치는 요인을 분석하였다. 그리고 또한 주말효과와 같은 시장효율성의 이례 현상에 대한 최근 연구에서 그전과 다른 기류에 대한 연구결과가 보고되기 시작하였다. 그리하여 그전의 자료와 최근의 10여 년간의 자료를 나누어 세계 각 주요시장의 주말효과에 대한 연구를 재검토 할 필요가 있었다. 본고에서 분석한 결과 1990년대 이전에는 각 시장마다 주말효과가 강하지만 최근 10여 년 동안의 자료를 분석한 결과 주말효과가 나타난 국가의 시장은 거의 없었다. 그리고 본고에서 결제청산과정체계의 변화 및 전환이 주말효과 및 주중 일별수익률의 미치는 영향을 분석한 결과 결제청산과정의 종류나 또는 각 시장 상황에 따라 정도의 차이는 있지만 대체적으로 결제청산과정의 변화가 특정한 날의 일별 수익률 패턴에 영향을 미치고 또한 주말효과의 수준의 변화의 일부분은 이러한 결제청산과정의 영향을 받았다고 볼 수 있었다.

• Nuclear Engineering and Technology
• /
• 제31권1호
• /
• pp.17-28
• /
• 1999

A thermal-hydraulic analysis is conducted on the loss-of-coolant-accident (LOCA) during shutdown operation of YGN Units 3/4. Based on the review of plant-specific characteristics of YGN Units 3/4 in design and operation, a set of analysis cases is determined, and predicted by the RELAP5/MOD3.2 code during LOCA in the hot-standby mode. The evaluated thermal-hydraulic phenomena are blowdown, break flow, inventory distribution, natural circulation, and core thermal response. The difference in thermal-hydraulic behavior of LOCA at shutolown condition from that of LOCA at full power is identified as depressurization rate, the delay in peak natural circulation timing and the loop seal clearing (LSC) timing. In addition, the effect of high pressure safety injection (HPSI) on plant response is also evaluated. The break spectrum analysis shows that the critical break size can be between 1% to 2% of cold leg area, and that the available operator action time for the Sl actuation and the margin in the peak clad temperature (PCT) could be reduced when considering uncertainties of the present RELAP5 calculation.

• 한국항해학회지
• /
• 제1권1호
• /
• pp.27-44
• /
• 1977

The Maneuvering Indices of a ship are the values that decide the quantity of her motion in turning when her rudder is turned over to an angle to the starboard or the port. They consist of two kinds of indices, one of which is called index K and the other, index T. Index K decides a ship's turning ability and index T does the length of time delay of a normal turning motion after her rudder has finished the turn of an ordered angle. Generally, the values of the indices are calculated through some mathematic formulas with figures of her heading degrees recorded at a fixed time intervals during her Z test. The values of the same kind index of a ship appear differently according to the ship'sspeed, trim, rudder angle and loaded condition, etc. In this paper, the author analyzed all the amthematic formulas required to calculate the values of the indices in their forming process and examined them from the point of mathematics and dynamics and also actually figured out the values of maneuvering indices of the M.S. "HANBADA", the training ship of Korea Merchant Marine College through her Z test. The author supposed a case in which two same typed ships as the "HANBADA" in size, shape and conditions were approaching each other in meeting end on situation and each ship turned her rudder hard over to the starboard respectively when they approached to the distance of 3 times as long as the ship's length. The author worked out mathematic formulas calculating forward and transverse ship's motions within the above mentioned situation for the quantative analysis of the collision avoding action to certify whether they are in collision status or not. Applying the calculated values of the maneuvering indices of the "HANBADA" to the motion calculating formulas, the author found out the two ships were passing over each other with the clearing distance o 39m between their port quarters. With the above mentioned examinations and explanations, the author demonstrated that a ship's motion in any collision avoiding action can be shown with quantities of time and distance within reliable limit.istance within reliable limit.