• Title/Summary/Keyword: Reactor stability

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A Knowledge Based System for Reactive Power/Voltage Control Including Contingency (상정사고를 고려한 무효전력/전압제어 전문가 시스템)

  • 박영문;김두현
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.39 no.8
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    • pp.779-791
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    • 1990
  • This paper presents a knowledge based system to solve reactive power/voltage control problem in a power system. A need is recognized for new methods to alleviate a bus voltage limit violation more quickly when a power system becomes an emergency state due to contingency. To cope with this object, a set of indices concept which is used to make bus order list of reactive power injection priority is introduced. A set of indices, based on the overall system conditions, consists of steady state stability index, reactive power transmittance indes, voltage severity index and generator fuel cost index. This scheme and empirical rules of the knowledge on the basis of the human expert result in fast decision-making of the reactive power compensation devices since only the amount of devices is determined by the inference in the knowledge based system when the voltage violation is detected. In this approach, control devices such as shunt capacitor (reactor), transformer tap settings and generator voltages are utilized. Also the developed system herein can be used to minimize control action taken or generator fuel cost according to the user's option on the weighting factor. The results of a case study are also presented.

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A Design of Power System Stabilization for SVC System Using a RVEGA (실 변수 엘피트주의 유전알고리즘을 이용한 SVC 계통의 안정화 장치의 설계)

  • Chung, Hyeng-Hwan;Hur, Dong-Ryol;Lee, Jeong-Phil;Wang, Yong-Peel
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.50 no.7
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    • pp.324-332
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    • 2001
  • In this paper, it is suggested that the selection method of parameter of Power System Stabilizer(PSS) with robustness in low frequency oscillation for Static VAR Compensator(SVC) using a Real Variable Elitism Genetic Algorithm(RVEGA). A SVC, one of the Flexible AC Transmission System(FACTS), constructed by a fixed capacitor(FC) and a thyristor controlled reactor(TCR), is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage. The proposed PSS parameters are optimized using RVEGA in order to maintain optimal operation of generator under the various operating conditions. To decrease the computational time, real variable string is adopted. To verify the robustness of the proposed method, we considered the dynamic response of generator speed deviation and generator terminal voltage by applying a power fluctuation and three-phase fault at heavy load, normal load and light load. Thus, we prove the usefulness of proposed method to improve the stability of single machine-infinite bus with SVC system.

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Determination of BTB HVDC Operating Point in Metropolitan area (대도시 내 BTB HVDC 투입 시 운전점 결정 방안)

  • Lee, Jae Hyeong;Yoon, Minhan;Han, Changhee;Jang, Gilsoo
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.331-332
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    • 2015
  • Since $20^{th}$ century, along with the rapid industrial advancement, the concentrated urban development in specific large cities have made people migrate to those cities, thus causing problems in the power system stability. In case of Korea, more than 40% of the power system demand comes from the consumers in Seoul Metropolitan area and the rate is expected to increase. With the continuous increase of power demand, in order to meet the demand for system reliability improvement, the power system was multi-looped for reliability enhancement, the problem of fault current happened. In this situation, there are several methods for fault current reduction likes current limiting reactor, replacing circuit breaker, splitting busses, etc. But these methods reached its limit, power system needs more fundamental solutions such as grid segmentation. In this paper, we assume grid segmentation already has been progressed using VSC BTB HVDC. Then, this paper discusses operating point of HVDC in metropolitan area considering loss minimization and handy flow control. The simulation is proceeded on 2027 KEPCO system.

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Immobilization of Trigonopsis variabilis and Conversion of Cephalosporin C to 7$\beta$-(4-Caboxybutanamido)Cephalosporanic Acid (Trigonopsis variabilis의 고정화 및 Cephalosporin C로부터 7$\beta$-(4-Carbohybutanamido)Cephalosporanic Acid의 전환)

  • 김종균;임재윤
    • Microbiology and Biotechnology Letters
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    • v.22 no.3
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    • pp.296-303
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    • 1994
  • An immobilized Trigonopsis variabilis cells having an high activity of D-amino acid oxidase(DAO) was used to convert CPC into GL-7-ACA. The optimal pH of the reaction system was 8.0-8.5, and the optimal temperature was 40$\circ$C. When immobilized cell was used repeatedly in semi-batchwise reaction, the system retained 80% of the initial activity after used of 12 times for over 12 hours. The storage stability of the immobilized cell was maintained for 30 days at 4$\circ$C. The CPC concentration for the maximal reaction rate was about 30 mM and 40 mM for free and immobilized cells, respectively. Substrate inhibition of CPC concentration more than 50 mM was overcomed by 20~25% by immobilization. Pure oxygen supply into reaction system was most efficient in D-amino acid oxidase reaction. Continuous conversion to GL-7-ACA from CPC has been developed with an bioreactor system containing immobilized T variabilis cells. By opera- tion of the reactor for 5 hours, the average conversion yield of >80% and GL-7-ACA production of 40~45 mM per hour could be obtained.

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The Analysis of Characteristics of Flux-Lock Type SFCL with Adjustable Inductance Level in Current Limiting Operation (인덕턴스 조정에 따른 자속구속형의 전류제한특성분석)

  • Lee, Na-Young;Choi, Hyo-Sang;Park, Hyoung-Min;Cho, Yong-Sun;Nam, Gueng-Hyun;Lim, Sung-Hun;Park, Chung-Ryul
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.11a
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    • pp.157-158
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    • 2005
  • Superconducting fault currents(SFCLs) are expected to improve not only reliability but also stability of real power systems. The analysis on the single line-to-ground fault of the integrated three phase flux-lock type SFCL, which consists of three flux-lock reactor wound on an iron core in each single phase and three YBCO thin films, was investigated in current limiting operation characteristics. We compared 21turn numbers with 42turn numbers according to wound turn numbers each the coil 2 under the additive polarity winding operation between coil 1 and coil 2. The three phase flux-lock type SFCL using an iron core differently operates general three phase resistive SFCLs. When a single line-to-ground fault occurred, the SFCL's three units were quenched after fault onset. We confirmed effective current limiting operation characteristics with adjustable inductance level.

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Production of Itaconic Acid by Various Immobilization Methods (다양한 고정화 방법에 의한 이타콘산 생산)

  • 김승욱;박승원;이진석
    • Microbiology and Biotechnology Letters
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    • v.22 no.6
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    • pp.646-650
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    • 1994
  • Aspergillus terreus NRRL 1960 was immobilized on various alginate gel beads, Celites, and polyurethane foam cubes, and the comparisons were made for the production of itaconic acid according to the types and sizes of each carrier. The levels of itaconic acid produced from Ca- alginate and Sr-alginate were similar, and the addition of bentonite to Ca- and Sr-alginate resulted in an increase of itaconic acid. The addition of 1.67% bentonite and 0.33% starch to Sr-alginate (SABS bead) produced higher level of itaconic acid (11.59 g/1) than other gel beads. A decrease in the size of Celite increased the itaconic acid production, and the smallest size of Celites, R- 634, produced 6.37 g/l of itaconic acid. Among various types of polyurethane foam cubes, HR 08 (2X2X2 cm) produced about 19 g/l of itaconic acid, which was more efficient than other carriers. In a repeated batch culture using immobilized cells on polyurethane foam cubes (HR 08, 2X2X2 cm), the stability of itaconic acid production was maintained up to 4 batches. Also, the possibility of itaconic acid production by continuous culture was shown in a packed-bed reactor.

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Stability of Antioxidant Properties and Essential Amino Acids in Squid Viscera Hydrolysate Produced using Subcritical Water

  • Kim, Ryoung-Hee;Asaduzzaman, A.K.M.;You, Chi-Hong;Chun, Byung-Soo
    • Fisheries and Aquatic Sciences
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    • v.16 no.2
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    • pp.71-78
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    • 2013
  • Subcritical water hydrolysis was carried out in a batch reactor to produce valuable materials, such as low-molecular weight (MW) peptides and essential amino acids with antioxidant properties, from heat-dried squid viscera. Hydrolysis of squid viscera was performed at 160 to $280^{\circ}C$ for 3 min. The yield was increased by increasing the temperature and pressure, while the protein content of squid viscera hydrolysate decreased with increasing temperature. Low-MW peptides were detected in all hydrolysates by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The highest yields of free and structural amino acids in heat-dried squid viscera hydrolysate were at $160^{\circ}C$ and were $411.95{\pm}1.15$ and $346.62{\pm}1.25$ mg/100 g, respectively. All essential amino acids were detected in viscera hydrolysates; leucine was the most abundant. Antioxidant activities of hydrolysates were highest at $220^{\circ}C$. Greater than $98{\pm}0.26%$ of the ABTS antioxidant activity was retained in hydrolysates after long-term heat treatment.

The Effects of Agglomeration of Catalyst on its Activity in Partial Oxidation Reforming (부분산화개질 반응에서 촉매의 응집이 촉매 활성에 미치는 영향)

  • Lee, Sang-Ho;Yoon, Sang-Ho;Jeon, Seung-Hyun;Bae, Jong-Myeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.11a
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    • pp.203-206
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    • 2009
  • Agglomeration of catalysts is known as one of the major degradation mechanisms. Reforming of liquid fuel, which requires high temperature over $800^{\circ}C$, accelerates agglomeration of catalysts. In this work, The effects of agglomeration on catalysts activity in partial oxidation reforming conditions were investigated. Metal supported catalysts(Pt-CGO, Ru-CGO) were compared to perovskite-structured catalysts(NECS-P1, NECS-P2). High thermal stability of perovskite-structured catalysts was reported. Micro-reactor installed in electric furnace was used. its Temperature was raised from $800^{\circ}C$ to $1000^{\circ}C$ to accelerate agglomeration effect. To measure rate of agglomeration, BET analysis and CO pulse chemisorption were conducted on catalysts exposed to $1100^{\circ}C$. Metal supported catalysts showed degradation at $1000^{\circ}C$ and The rates were different according to metal supported. On the other hand perovskite-structured catalysts showed no degradation at $1000^{\circ}C$.

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Evaluation of the Demineralizer Performance and $^{65}Zn$ Activity on Spent Resin for a Zinc Addition Operation

  • Kim, Kwang-Rag;Sung, Ki-Woung;Na, Jung-Won;Kim, Uh-Chul
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • 2003.11a
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    • pp.191-195
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    • 2003
  • Zinc acetate has been proposed and used to evaluate ionic zinc as a means to reduce reactor radiation buildup at several nuclear plants. Thermodynamic analysis of the aqueous zinc system using reliable data shows that the stability of the hydrolyzed zinc species increases with pH and temperature. Adsorption kinetics and isotherm studies were carried out to investigate the mixed resin performance of the zinc adsorption. The equilibrium isotherms of the zinc adsorption onto nuclear grade resin indicate that the data correlate well with the Langmuir model and that the adsorption is physical in nature. The maximum capacity according to the Langrnuir model is about 0.6meq/g for an initial zinc concentration of 100ppm at $50^{\circ}C$. The use of natural zinc could result in the generation of a $^{65}Zn$ activity with about $500{\mu}Ci/mL$ of resin after 12 months of operation.

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CO2 sequestration and heavy metal stabilization by carbonation process in bottom ash samples from coal power plant

  • Ramakrishna., CH;Thriveni., T;Nam, Seong Young;kim, Chunsik;Ahn, Ji Whan
    • Journal of Energy Engineering
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    • v.26 no.4
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    • pp.74-83
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    • 2017
  • Coal-fired power plants supply roughly 50 percent of the nation's electricity but produce a disproportionate share of electric utility-related air pollution. Coal combustion technology can facilitate volume reduction of up to 90%, with the inorganic contaminants being captured in furnace bottom ash and fly ash residues. These disposal coal ash residues are however governed by the potential release of constituent contaminants into the environment. Accelerated carbonation process has been shown to have a potential for improving the chemical stability and leaching behavior of bottom ash residues. The aim of this work was to quantify the volume of $CO_2$ that could be sequestrated with a view to reducing greenhouse gas emissions and stabilize the contaminated heavy metals from bottom ash samples. In this study, we used PC boiler bottom ash, Kanvera reactor (KR) slag and calcined waste lime for measuring chemical analysis and heavy metals leaching tests were performed and also the formation of calcite resulting from accelerated carbonation process was investigated by thermo gravimetric and differential thermal analysis (TG/DTA).