• International Journal of Fluid Machinery and Systems
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• v.8 no.2
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• pp.73-84
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• 2015

Aerating hydroturbines have recently been proposed as an effective way to mitigate the problem of low dissolved oxygen in the discharge of hydroelectric power plants. The design of such a hydroturbine requires a precise understanding of the dependence of the generated bubble size distribution upon the operating conditions (viz. liquid velocity, air ventilation rate, hydrofoil configuration, etc.) and the consequent rise in dissolved oxygen in the downstream water. The purpose of the current research is to investigate the effect of location of air injection on the resulting bubble size distribution, thus leading to a quantitative analysis of aeration statistics and capabilities for two turbine blade hydrofoil designs. The two blade designs differed in their location of air injection. Extensive sets of experiments were conducted by varying the liquid velocity, aeration rate and the hydrofoil angle of attack, to characterize the resulting bubble size distribution. Using a shadow imaging technique to capture the bubble images in the wake and an in-house developed image analysis algorithm, it was found that the hydrofoil with leading edge ventilation produced smaller size bubbles as compared to the hydrofoil being ventilated at the trailing edge.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1107-1113
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• 2015

Test temperature is an important factor affecting the measurement results of dielectric response of field power transformers. In order to better apply the polarization and depolarization current (PDC) to the condition monitoring of oil-paper insulation system in power transformers, the influences and elimination method of test temperature on PDC characteristic spectroscopy (PDC-CS) were investigated. Firstly, the experimental winding sample was measured by PDC method at different test temperatures, then the PDC-CS was obtained from the measurement results and its changing rules were discussed, which show that the PDC-CS appears a horizontal mobility with the rise of temperature. Based on the rules, the “time temperature shift technique” was introduced to eliminate the influence of test temperature. It is shown that the PDC-CS at different test temperatures can be converted to the same reference temperature coincident with each other.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1863-1864
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• 2008

한국전력거래소에서 운영중인 EMS(Energy Management System)와 MOS(Market Operation System) 설비는 각각 Alstom사와 ABB사에 의해 우리나라의 전력계통 특성에 맞게 제작되어 공급된 전력계통과 전력시장의 운영을 자동화한 시스템이다. EMS는 전력계통 감시와 효율적인 운영을 위해 전력계통을 모델링한 데이터를 활용하며, MOS는 실시간 급전계획 수립을 위한 기반자료로 전력계통을 모델링한 데이터를 사용하게 된다. 그러나, 대한민국 전력산업의 핵심인 두 시스템은 시스템 설계 방식 및 DB 구조가 상이하여 전력계통의 신.증설 및 변경 시 동일한 데이터를 양 시스템에 각각 따로 구축, 운영해야하는 실정이다. 이에 따라 DB작업을 위한 자료 준비부터 입력, 수정, 검증 등 모든 과정에 중복된 관리가 이루어지고 있다. 중복 관리는 양 시스템 간 DB의 주요 데이터 특성 및 명칭이 상이하여 일률적인 관리가 어렵고, 시스템별 특성 및 운영노하우가 없이는 인적실수에 의한 입력오류 개연성이 폭넓게 존재하는 등 현 상황에서 피할 수 없는 현실이었다. EMS와 MOS 시스템 중 최소한 개의 시스템을 전면 재구축하지 않으면 해결되지 않을 본 문제를 해소하기 위하여 전력거래소는 특정 시스템에 구축된 데이터를 변환알고리즘을 통해 나머지 하나의 시스템에 자동 구축할 수 있는 시스템을 개발하여 활용하고자 한다. 이것이 바로 EMS에 입력되어 정확성이 검증된 계통데이터를 추출하여 MOS의 데이터 형식으로 변환하고, 변환된 데이터를 MOS시스템에 자동으로 입력할 수 있는 MOS/EMS 데이터 자동변환시스템이다.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.20-30
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• 2013

An intelligent grid computing architecture is proposed and developed for transient stability constrained total transfer capability evaluation of future smart grid. In the proposed intelligent grid computing architecture, a model of generalized compute nodes with 'able person should do more work' feature is presented and implemented to make full use of each node. A timeout handling strategy called conditional resource preemption is designed to improve the whole system computing performance further. The architecture can intelligently and effectively integrate heterogeneous distributed computing resources around Intranet/Internet and implement the dynamic load balancing. Furthermore, the robustness of the architecture is analyzed and developed as well. The case studies have been carried out on the IEEE New England 39-bus system and a real-sized Chinese power system, and results demonstrate the practicability and effectiveness of the intelligent grid computing architecture.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.346-352
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• 2009

The objective of the present work is to improve numerical predictions of unsteady turbulent swirling flows in the draft tubes of hydraulic power plants. We present Large Eddy Simulation (LES) results on a simplified draft tube consisting of a straight conical diffuser. The basis of LES is to solve the large scales of motion, which contain most of the energy, while the small scales are modeled. LES strategy is here preferred to the average equations strategies (RANS models) because it resolves directly the most energetic part of the turbulent flow. LES is now recognized as a powerful tool to simulate real applications in several engineering fields which are more and more frequently found. However, the cost of large-eddy simulations of wall bounded flows is still expensive. Bypass methods are investigated to perform high-Reynolds-number LES at a reasonable cost. In this study, computations at a Reynolds number about 2 $10^5$ are presented. This study presents the result of a new near-wall model for turbulent boundary layer taking into account the streamwise pressure gradient (adverse or favorable). Validations are made based on simple channel flow, without any pressure gradient and on the data base ERCOFTAC. The experiments carried out by Clausen et al. [1] reproduce the essential features of the complex flow and are used to develop and test closure models for such flows.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1032-1038
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• 2008

KTX train system is composed of TORNAD* network for transmitting information of train's internal equipments and OBCS which proceed information within train. OBCS of one trainset consisted of 28 equipments takes intelligent and dynamic composition according to equipment handling, train command and control flow. Each OBCS which is installed within trainset handle and supervise mutually action information about equipments, transmit it to driver to transmit information about train operation and preventive management. This mutual supervision and information transmission use KTX TORNAD* network system. TORNAD* network system is the one which is uniquely developped by GEC ALSTHOM, the KTX trainset manafacturing provider and this field is excluded from technical know-how transfer item. Through the research on analysis method of KTX TORNAD* system data structure which is operating on Seoul-Pusan Line, I hope that this thesis can contribute to train network system's standardization after applying it to improvement of train network system maintenance, enhancing quality of train service and applying it to future Korean rolling stock network system development.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.380-381
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• 2011

전력거래소는 2014년 나주본사이전 이후 1억kW 대용량 전력계통을 운영하기 위한 차기 계통운영시스템(이하 차기EMS) 구축을 계획하고 있다. EMS(Energy Management System)는 전국의 발, 변전소에서 계통정보를 실시간으로 취득하여 전력계통을 감시하며, 연료비 기반의 최적 경제점을 찾아 발전기를 제어하고, 전력계통을 수식화한 상태추정 결과를 기반으로 상정사고분석, 고장전류계산 등 전력계통운영을 위한 종합시스템이다. 국내 EMS의 역사는 1979년 미국의 L&N 시스템 도입을 시작으로 1988년 일본의 Toshiba EMS, 2001년 Alstom사의 NEMS를 구축하여 현재 운영중에 있다. 하지만, 외산 제품 도입에 따른 기술이전, 유지보수의 어려움을 타개하기 위해 2004년 한국형 EMS(이하 K-EMS) 연구개발계획을 수립하고 전력거래소를 주축으로 한 산학연을 구성하여 2010년 K-EMS 개발을 성공적으로 완료하였다. 차기 EMS는 국내 기술력으로 개발된 정부연구과제 성과물인 K-EMS를 기반으로 구축이 이루어지며, 총 3년간의 개발 및 시험과정을 거쳐 실계통운영을 담당할 예정이다. 차기EMS가 설치되어 운영예정인 급전소는 전력수급 균형유지와 발전소 운영 총괄 지휘 및 765kV, 345kV 송전망 운영역할을 담당할 나주급전소와 154kV 비수도권 송전망 운영을 담당할 천안급전소, 154kV 수도권 송전망 운영을 책임질 서울급전소 이상 3곳이다. 차기EMS는 발전 및 송, 변전 설비의 대형화, 다양한 FACTS 설비, 신재생에너지원으로 대표되는 분산전원의 등장과 같은 급변하는 전력계통 변화에 능동적인 역할을 성공적으로 수행할 것으로 기대하고 있다.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.87-93
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• 2014

The KTX, running in Korea but imported from Alstom Co. in France, has folding type staircases complying with European standard EN 4752. However, when operating, the step size is only 200mm, while the Korean standard step size is 253mm, a standard reflecting the average value of persons aged 20~60. From the aspect of kinesiology, the current step size can cause falls or slips during embarking and disembarking of passengers because body load is mostly focused on the heel and the current step is much more narrow than the standard size. Thus, we have performed an analytical study to check the safety of folding type staircases on the KTX after re-design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3632-3637
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• 2009

In this paper, we describe the performance results of the field installation test which is required to practicalize the single-phase MJ81 Switch Point Machine. This product has passed the certified test through performance improvement of driving parts in order to use 3 phase MJ81 Switch Point Machine, which is localized by taking over technology from Alstom and Cogifer when constructing Seoul-Busan rapid-transit railway, without change of the electrical equipment at track-side in domestic existing lines which single-phase 220V is used. KRRI and Samsung SDS have localized the single-phase MJ81 Switch Point Machine to improve the speed and safety of the conventional lines through the existing railway technology development project. For practicalization of this, we should, however, verify the performance through not only field installation test in real lines but also interface test with the interlocking. In this paper we verify the practicality of the domestic single-phase MJ81 Switch Point Machine through analysis on the performance result of the field installation test as well as the research contents for this test. Thereby, in Feb 2009 we have received an order from the Korea Rail Network Authority and are currently installing the single-phase MJ81 Switch Point Machine.