• Title, Summary, Keyword: limiting magnitude

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Effect of inserting resistance's magnitude on OCR trip time in a short-circuit of distribution system (배전계통 사고시 투입저항 크기가 OCR트립 시간에 미치는 영향)

  • Ahn, Jae-Min;Kim, Jae-Chul;Lim, Sung-Hun;Kim, Jin-Seok;Moon, Jong-Fil
    • Proceedings of the KIEE Conference
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    • pp.154-155
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    • 2007
  • Increase of fault current due to larger power demand has increased the possibility of the breakdown of the power system. To protect the power system effectively from the larger fault current, several countermeasures have been proposed. Among them, the superconducting fault current limiter (SFCL) has been expected as one of the most effective solutions. In this paper, the fault current limiter, which consists of a ideal switch as a trigger part and the limiter as the limiting part, has been applied into the distribution system. From the analysis for the fault current limiting operation of SFCL, the inserting resistance's magnitude has been confirmed to affect OCR trip time in a short-circuit of distribution system.

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An analysis of limiting conditions of excess inrush currents and a derivation of the probability equations of inrush current occurrence (돌입전류의 제어조건 해석 및 돌입전류 발생 확률식의 유도)

  • 박영문
    • 전기의세계
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    • v.14 no.5
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    • pp.8-14
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    • 1965
  • Because of the flat slope of the magnetic characteristic curves at high saturation, the transformer inrush current peakes may assume an extreme magnitude. Even though such is rarely any danger to the transformer itself, the currents can cause serious problems in associated apparatus. This paper has analyzed various limiting factors of excess inrush currents, and then has suggested how to determine the frequency of encountering the inrush current peaks higher than an arbitrarily chosen value by deriving the probability equations of inrush current occurrence.

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Kinetics and Mechanism of the Reactions of S-Phenyl Dithiobenzoates with Benzylamines in Acetonitrile

  • 오혁근;신철호;이익춘
    • Bulletin of the Korean Chemical Society
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    • v.16 no.7
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    • pp.657-661
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    • 1995
  • Kinetic studies are carried out on the reaction of S-phenyl dithiobenzoates with benzylamines in acetonitrile at 30.0 ℃. Small magnitude of ρX (βX) as well as ρZ (βZ) obtained suggests rate-limiting nucleophilic attack of the thiocarbonyl carbon. This is supported by the unusually small magnitude of ρXY and ρYZ, albeit their signs do not agree with those expected. Moreover, the inverse secondary kinetic isotope effects (kH/kD<1.0) involving deuterated benzylamine nucleophiles are also in line with the proposed mechanism.

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Variations of Initial Fault Current Limiting Instant According to Fault Angles in the Flux-lock Type SFCL (자속 구속형 전류제한기의 사고각에 따른 초기 사고전류 제한 시점 변화분석)

  • Park, Chung-Ryul;Lim, Sung-Hun;Park, Hyoung-Min;Choi, Hyo-Sang;Han, Byoung-Sung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.61-64
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    • 2004
  • In this paper, we investigated the variations of initial fault current limiting instant according to fault angles in the flux-lock type SFCL. The flux-lock type SFCL consists of the coil 1 and the coil 2 that are wound in parallel each other through an iron core. The operation of the flux-lock type SFCL can be divided into the subtractive polarity winding and the additive polarity winding operations according to the winding directions between the coil 1 and coil 2. The subtractive polarity winding operation could be analyzed with three modes. On the other hand, the additive polarity winding operation could be analyzed with five modes. The variations of initial fault current limiting instant in two winding directions were dependent on the fault angles. It was confirmed from experiment that the fault current limiting instant was getting faster and the magnitude of fault current at the initial fault time was getting higher for higher fault angle.

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Theoretical Studies on the Reactions of Acetate Esters with Substituted Phenolate Anion Nucleophiles$^1$

  • Im, Ung Muk;Kim, Wang Gi;Jeong, Hak Jin;Lee, Ik Jun
    • Bulletin of the Korean Chemical Society
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    • v.16 no.3
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    • pp.252-256
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    • 1995
  • Semiempirical MO calculations using the PM3 method are performed on the reactions of acetate esters with substituted phenolate anions. The mechanistic change from rate-limiting formation to breakdown of the anionic intermediate is shown to occur in the gas-phase, especially for meta-nitrophenyl acetate. However the mechanistic change-over takes place at a lower basicity ($pK_0$) of the anion nucleophile than found for the corresponding formate. This lowering of $pK_0$ has been ascribed to the electron donating effect of the methyl group in the acetate. For the reactions involving rate-limiting breakdown of the intermediate, the large Bronsted coefficients, ${\beta}_X({\beta}_{nuc})$, are expected in general, but the magnitude increases to a larger value and the pK0 is lowered accordingly, when an electron-donating nonleaving group, like $CH_3$, is present. This type of nonleaving group effect provides a necessary condition for the carbonyl addition-elimination mechanism with rate-limiting breakdown of the intermediate.

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Preamplier design for IR receiver IC (적외선 수신모듈IC용 전치증폭기의 설계)

  • Hong, Young-Uk;Ryu, Seung-Tak;Choi, Bae-Gun;Kim, Sang-Kyung;Baik, Sung-Ho;Cho, Gyu-Hyeong
    • Proceedings of the KIEE Conference
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    • pp.3124-3126
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    • 2000
  • The application of IR(Infrared) communication is very wide and IR receiver has become a standard of home entertainment. A preamplifier with single 5V supply was designed for IR receiver IC. To operate at long distance, receiver IC should have high gain and low noise characteristic. To provide constant output signal magnitude, independent of transciever distance, gain limiting stage is needed. And to cut-off DC noise component effectively, large resistance and capacitance are required. Transimpedance type preamplifier, and diode limiting amplifier, and current limiting amplifier were designed. It is another function of current limiting amplifier that transforms single input signal to differential output signal. Using AMS BiCMOS model, both BJT version and MOS version was designed. Total power consumption is O.lmW, and IC size is $0.3mm^2$

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Current Limiting Characteristics according to Applied Voltage Increase of Resistive-type SFCL using YBCO Coated Conductor (YBCO Coated Conductor를 이용한 저항형 전류제한기의 인가전압 증가에 따른 전류제한 특성)

  • Du, Ho-Ik;Kim, Min-Ju;Doo, Seung-Gyu;Kim, Yong-Jin;Lee, Dong-Hyeok;Han, Byoung-Sung
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.10
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    • pp.854-859
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    • 2009
  • The YBCO coated conductor is an important element that forms the superconducting power equipment. The first advantage of applying YBCO coated conductor to superconducting power equipment is that it can effectively addresses the normal and fault currents using less quantity of wire than when using Bi tape due to its high critical current density. Second, it can limit the fault current fast because its index value is high. so that the resistance can be produced fast when it is applied to the superconducting current limiting element. Third, the type of stabilization layer that surrounds the YBCO superconductor is selectable and the magnitude of the resistance that is produced from quenching can be adjusted. This study researched into the manufacture of current-limiting element of using YBCO coated conductor, into the characteristics of current limiter that considered by combining the manufactured element with the resistive-type superconducting fault current limiter.

Variability of Water Quality and Limiting Factor for Primary Production in Semi-enclosed Masan Bay, South Sea of Korea (한국 남해 마산만에서 수질환경의 계절적 변동과 기초생산 제한인자)

  • Lim, Dhong-Il;Kim, Young-Ok;Kang, Mi-Ran;Jang, Pung-Kuk;Shin, Kyoung-Soon;Jang, Man
    • Ocean and Polar Research
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    • v.29 no.4
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    • pp.349-366
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    • 2007
  • Seasonal variations of various physicochemical components (temperature, salinity, pH, DO, COD, DOC, nutrients-silicate, DIN, DIP) and potential limiting factor for phytoplankton primary production were studied in the surface water of semi-enclosed Masan Bay. Seasonal variations of nutrient concentrations, with lower values in summer and winter, and higher in fall, are probably controlled by freshwater loadings to the bay, benthic flux and magnitude of occurrence of phytoplankton communities. Their spatial distributional patterns are primarily dependent on physical mixing process between freshwater and coastal seawater, which result in a decreasing spatial gradient from inner to outer part of the bay. In the fall season of strong wave action, the major part of nutrient inputs (silicate, ammonium, dissolved inorganic phosphorus) comes from regeneration (benthic flux) at sediment-water interface. During the summer period, high Si:DIN and Si:DIP and low DIN:DIP relative to Redfield ratios suggest a N- and secondarily P-deficiency. During other seasons, however, silicate is the potential limiting factor for primary production, although the Si-deficiency is less pronounced in the outer region of the bay. Indeed, phytoplankton communities in Masan Bay are largely affected by the seasonal variability of limiting nutrients. On the other hand, the severe depletion of DIN (relatively higher silicate level) during summer with high freshwater discharge probably can be explained by N-uptake of temporary nanoflagellate blooms, which responds rapidly to pulsed nutrient loading events. In Masan Bay, this rapid nutrient consumption is considerably important as it can modify the phytoplankton community structures.

A Burst-Mode Limiting Amplifier with fast ATC Function (고속 ATC 기능을 갖는 버스트-모드 제한 증폭기)

  • Ki, Hyeon-Cheol
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.46 no.10
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    • pp.9-15
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    • 2009
  • In this paper, we invented a new structure of fast ATC(Automatic Threshold Control) circuit. Using the structure we made a new burst-mode limiting amplifier with fast ATC function using commercial $0.8{\mu}m$ BiCMOS technology. It's ATC function worked so fast that even the first bit of burst-data could be detected, which confirmed that the new structure was useful for fast ATC. However, in the beginning of a burst, distortions in duty-cycle occurred and increased up to 59% of duty-cycle as amplitude of input signal increased. But we confirmed that after 10 cycles passed, duty-cycles was staying below 52% of duty-cycle for any magnitude of input signal.

A Study on the Electromagnetic Transients in A Power System (전력계통의 전자과도현상에 관한 연구)

  • 김경철;강창원;이일무
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • pp.59-64
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    • 2001
  • Transient in an electrical system are generated by lightning and switching. This paper presents analysis of switching and lightning surge, and means of limiting the voltage magnification transient for high voltage power systems by using EDSA's EMTAP software package. One means of limiting the voltage magnification transient is to convert the end-user power factor correction banks to harmonic filters. An inductance in series with the power factor correction bank was used to decrease the transient voltage at the customer bus to acceptable levees. The interception of the impulse from the phase wire is fairly straight forward by properly installed surge arresters. The simulation shows that the addition of the surge arrester at the customer location can achieve a substantial reduction of the transient magnitude.

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