• 한국초전도ㆍ저온공학회논문지
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• 제9권1호
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• pp.37-42
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• 2007

We are developing a 22.9 kV/25 MVA superconducting fault current limiting(SFCL) system for a power distribution network. A Bi-2212 bulk SFCL element, which has the merits of large current capacity and high allowable electric field during fault of the power network, was selected as a candidate for our SFCL system. In this work, we experimentally investigated important characteristics of the 190 kVA Bi-2212 SFCL element in its application to the power grid e.g. DC voltage-current characteristic, AC loss, current limiting characteristic during fault, and so on. Some experimental data related to thermal and electromagnetic behaviors were also compared with the calculated ones based on numerical method. The results show that the total AC loss at rated current of the 22.9 kV/25 MVA SFCL system, consisting of one hundred thirty five 190 kVA SFCL elements, becomes likely 763 W, which is excessively large for commercialization. Numerically calculated temperature of the SFCL element in some sections is in good agreement with the measured one during fault. Local temperature distribution in the190 kVA SFCL element is greatly influenced by non-uniform critical current along the Bi-2212 bulk SFCL element, even if its non-uniformity becomes a few percentages.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.750-752
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• 2002

An HTS power cable has multi-layer conductor structure to increase the current capacity. However, usually the current is not evenly distributed among the layers. This paper describes a method to make the current distribution more uniform and hence reduce the AC loss. Also. this paper shows recommendation for future cable conductor prototypes.

• 전기학회논문지P
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• 제58권2호
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• pp.227-230
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• 2009

In this paper, we performed the optimum design of reactors for matrix-type superconducting-fault current limiters (SFCLs), using electromagnetic analysis tools. We decided a optimun position within a reactor for superconducting elements of current-limiting parts and trigger parts from the calculation of magnetic flux internsity for reactor structures. Also we decided effective distance length between two reactors through the analysis of the distribution of magnetic field, according to distance lengths between them. We designed and characterized matrix-type SFCLs, based on our optimum design of a reactor. We confirmed uniform distribution of a fault current, resulted from the improvement of simultaneous quench characteristics within our matrix-type SFCL.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1365-1370
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• 2013

This paper examines the effects of magnetic induction attenuation on current distribution in the exit regions of the Faraday-type, non-equilibrium plasma Magnetohydrodynamic (MHD) generator by numerical calculation using cesium-seeded helium. Calculations show that reasonable magnetic induction attenuation creates a very uniform current distribution near the exit region of generator channel. Furthermore, it was determined that the current distribution in the middle part of generator is negligible, and the output electrodes can be used without large ballast resistors. In addition, the inside resistance of the exit region and the current concentration at the exit electrode edges, both decrease with the attenuation of magnetic flux density. The author illustrates that the exit electrodes of the diagonal Faraday-type, non-equilibrium plasma MHD generator should be arranged in the attenuation region of the magnetic induction, in order to improve the electrical parameters of the generator.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1398-1400
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• 2005

A novel data driver for passive matrix organic lightemitting devices (PM-OLEDs) with high gray scale images was designed. The proposed circuit consisted of a main current bias circuit as well as sample & hold circuits in each channel of the data driver to compensate a current offset. These results indicate that a data driver designed by using the current offset compensation technique holds promise for poten tial applications in PM-OLED displays with high gray scale images.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.350-353
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• 2005

Microstructures according to experimental conditions (pouring temperature, stirring current and stirring time) and hardness according to aging time were investigated for A356 cast aluminum alloy and 7075 wrought aluminum alloy. In pouring temperature control, grains became larger and non-uniform at high temperature, however dendritic shapes were shown at lower temperature. In stirring current control, dendritic grains were not destroyed enough at lower current, however fine grains were agglomerated at higher current. And, in stirring time control, grains were more globular but grew larger and larger with the stirring time increasing.

• Journal of Information Display
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• 제5권4호
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• pp.23-26
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• 2004

A limitation of oxide cathode is the high current density, caused by low electrical conductivity of an emitter layer. This limitation can be overcome by increasing the conductivity, and uniform dispersion of Ni powder and pore agent could be achieved by using the screen-printing method. This new cathode has shown not only high current density reliability but also improved performance characteristics and as such given the name "Multi-Function cathode". It is expected to be a good replacement of the impregnated cathode.

• 전기의세계
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• 제30권4호
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• pp.231-236
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• 1981

It has been known that D.C. breakdown Voltage is lower than A.C. breakdown Voltage in insulatingoil, but there are still many unvivid points at electric conduction in breakdown or under of high electric field. This study measured the electric current-electric field characteristics (I-E characteristics) and the breakdown Voltage under of D.C. electric field of insulating oil using the system of electrodes that are near the Uniform electric field with a result. I can study, electric conduction in area of high electric field depends upon the Schottky effect. The liquidity of breakdown electric field takes place by the local concentration of electric field. The longer gap is and the more electric current is the more breakdown Voltage decreased. There are not almost the change of electric current-electric field characteristics by materials of electrode.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.383-386
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• 1999

Surge arrestor is used for protection of facilities and lines. Recently lots of arresters fatted prematurely In the distribution lines. It is important to know that what the cause of the failures is. This paper presents characteristics of the aged and new 18kV surge arrester. In order to analyse characteristics, we measured leakage current using specialty made leakage current measurement system and also investigated Tan $\delta$ of the arrester and microstructure of the elements. Through the investigation we found that the characteristics among the ZnO elements in an arrester were a little different, It means that the surge arreste can have non-uniform electric field due to the characteristic difference of The each element. Owing to this concentration of the electric field, the localized aging might be proceeded.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.109-112
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• 2003

Small impedances in the superconducting parallel circuits cause unequal distribution of the currents in the circuits. This results in quenches or losses in some superconducting parts and decrease of total transport current. This paper presents the fabrication and test results of a superconducting multi- interphase transformers (SIPT) for equal current distribution in superconducting parallel circuits. The secondary loop configuration with air core SIPT seems to be the most efficient one for the SFCL. Test results show that the SIPT can effectively make the current distribution uniform in Parallel circuits that have unequal resistances.