• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.107-110
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• 2003

High Temperature Superconductor (HTS) transmission cable can carry more than 2 to 5 times higher electricity and also obtain substantially lower transmission losses than conventional cables. Liquid nitrogen is to be used to cool the HTS power cable and its cost is much cheaper than the liquid helium used for the cooling of metal superconducting wire. In Korea the HTS power cable development project has been ongoing since July, 2001 with the basic specifications of 22.9kV, 50MVA and told dielectric type as the first 3-year stage. The cryogenic system of the HTS cable is composed of HTS cable cryostat termination and refrigeration system. Termination of HTS cable is a connecting part between copper electrical cable at room temperature and HTS cable at liquid nitrogen temperature. In order to design the termination cryostat, it is required that the conduction heat leak and Joule heating on the current lead be reduced, the cryostat be insulated electrically and good vacuum insulation be maintained during long time operation. Heat loads calculations on the copper current lead have been performed by analytical and numerical method and the feasibility study fer the other candidate materials has also been executed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1047_1048
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• 2009

This paper describes comparative analysis results about the dynamic interaction of interconnected wind power system using the actual-size hardware simulator and the simulation model with PSCAD/EMTDC. The hardware simulator, which is composed of 2.0MVA induction motor with drive system and 1.5MW doubly-fed induction generator, was built and tested in Go-Chang Test Site of KEPCO for analyzing the dynamic interaction with the interconnected distribution system. The operation of hardware simulator was verified through comparative analysis between experimental results and simulation results obtained by simulation model with PSCAD/EMTDC. The developed hardware simulator and simulation model could be effectively used for analyzing the dynamic interaction, which has various phenomena depending on the wind variation and the network state of interconnected power system.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.3
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• pp.263-269
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• 2009

This paper describes comparative analysis results about the dynamic interaction of interconnected wind power system using the actual-size hardware simulator and the simulation model with PSCAD/EMTDC. The hardware simulator, which is composed of 2.0MVA induction motor with drive system and 1.5MW doubly-fed induction generator, was built and tested in Go-Chang Test Site of KEPCO for analyzing the dynamic interaction with the interconnected distribution system. The operation of hardware simulator was verified through comparative analysis between experimental results and simulation results obtained by simulation model with PSCAD/EMTDC. The developed hardware simulator and simulation model could be effectively used for analyzing the dynamic interaction, which has various phenomena depending on the wind variation and the network state of interconnected power system.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.865-867
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• 2001

Generally large synchronous rotating machines with 2 poles have more merits than the others with more than 2 poles Superconducting synchronous rotating machines also have the same tendency, but they have different structure from conventional ones because of no magnetic core inside of the rotor. As the result, design approaches of the superconducting field coils are also different, which would be classified into 2 types according to their coil shapes. The first one is race-track type and the other is saddle type Race-track type machines have almost the same structure with conventional salient pole generators which are being used as largely small scale machines with more than 2 poles. On the other hand saddle type machines correspond to conventional cylindrical generators with 2 poles used for large turbine system in power plants. In this paper several types of superconducting field coils are introduced for 2 pole superconducting machine design and then the feasibility of each type is considered. Moreover, based on the consideration. 1MVA superconducting generator(S.G.) with saddle type field coil is designed electromagnetically.

• Progress in Superconductivity and Cryogenics
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• v.6 no.4
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• pp.32-36
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• 2004

AC loss is one of the important parameters in HTS (High Temperature Superconducting) AC devices. Among the HTS AC power devices, the transformer is an essential part in electrical power system. But, AC loss is one of the most serious problems of the HTS transformer, especially with pancake windings, because high alternating magnetic field is applied perpendicularly to the surface of BSCCO wire in HTS windings of that, comparing with the other HTS AC power devices. For the reason above the calculation of AC loss generated in the HTS windings should be carried out in advance when designing the HTS transformer. In the paper we performed study for optimization of winding design to minimize the magnetization loss of HTS winding such as the spaces between pancake windings and operating temperature of HTS wire. The calculation of the AC loss was accomplished by 2-demensional Finite Element Method.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.408-409
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• 2015

한국전력공사에서는 2015년 4월말 기준 808개의 변전소를 운전 중에 있다. 변압기 용량으로 보면 299,734MVA에 달하고 있으며, 매년 증가하는 전력수요에 맞추어 신규 변전소 건설과 더불어 변전설비가 계속하여 확충되고 있다. 또한, 계절별 및 시간대별 부하변동에 따른 변전소 모선의 전압변동에 대응하기 위하여 Sh.C(Shunt Condenser), Sh.R(Shunt Reactor), SVC(Static Var Compensator) 등 다양한 무효전력보상 및 조절 설비들이 지속적으로 설치되고 있다. 이들 무효전력보상 설비들은 주로 변전소 모선에 전용 차단기를 통하여 연결되어 운전되고 있으며, 전용 차단기는 매일 시간대별 부하변동에 대응하여 개폐빈도가 많은 다빈도 차단기로서 잦은 개폐조작에 따른 내구성이 필요하며 변전소 모선전압을 기준전압 범위 이내로 안정적으로 유지하기 위한 신뢰성이 요구되고 있다. 본 논문에서는 345kV Sh.R 개폐용 동일유형의 345kV 50kA 1점절 다빈도 차단기에서 차단조작시 발생한 차단부 절연파괴 고장의 원인을 분석하고 재발방지를 위한 대책에 대하여 논하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.285-296
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• 2017

This paper proposes an improved modulation scheme for the medium voltage modular multi-level converter (MMC), which operates in the nearest level control and applies in the medium voltage direct current (MVDC) system. In the proposed modulation scheme, the offset (neutral-to-zero output) voltage is adjusted, with the phase voltage magnitude, thereby maintaining a constant value with N+1 level in the controllable modulation index (MI) range. In order to confirm the proposed scheme's validity, computer simulations for the 22.9 kV - 25 MVA MMC were performed with PSCAD/EMTDC, as well as hardware experiments for the 380 V - 10 kVA MMC. The proposed modulation scheme offers to build a constant pole voltage regardless of the MI value, and to build a phase voltage with improved total harmonic distortion (THD).

• Journal of Microbiology and Biotechnology
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• v.12 no.5
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• pp.716-721
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• 2002

The ldhL gene encoding the $_L$-(+) lactate dehydrogenase was cloned from Lactobacillus reuteri ATCC 55739 chromosomal DNA and characterized. An internal 750-bp fiagment of ldhL gene was amplified by PCR using primers based on the conserved region of lactobacilli ldhL genes. A genomic library off. reuteri ATCC 55739 was constructed using pBR322, and colony hybridization experiments were performed using the 750-bp fragment as aprobe. One clone harboring a 4.0-kb PstI fragment was identified, and nucleotide sequencing confirmed it as an open reading frame of 972 bp in size in the middle. In addition to IdhL gene, an ORF homologous to Streptococcus pneumoniae TIGR4 hydrolase gene and 3' part of phosphomevalonate kinase gene (mvaK2) were also found on the 4 kb fragment. $_L$-LDH of L. reuteri ATCC 55739 showed the highest degree of homology with the $_L$-LDH of Pediococcus acidilactici (62.4%), fullowed by the $_L$-LDH of Lactobacillus pentosus (58.7%). The size of IdhL transcript determined by Northern blot was 1 kb, indicating the monocistronic nature of IdhL.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.19-22
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• 2003

In the response to increasing the demands for electrical energy, much effort aimed to develop and commercialize 1MVA HTS power equipments that is supported by a grant from center for Applied Superconductivity Technology of the 21st Century Frontier R&D Program funded by the Ministry of Science and Technology is going on in Korea. For the development, the cryogenic insulation and winding insulation of it in this paper are discussed. In the first many types of dielectric insulating tests were carried out. In detail Breakdown characteristics of $LN_2$, FRP and turn insulating films, flashover characteristics along the FRP surface in $LN_2$ were verified after distinguishing insulation components in HIS windings. And then model windings were designed and insulation test was conducted. These included a AC withstand voltage test of 50kV rms and a lightning impulse test of 150kV at peak.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.229-231
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• 1999

For the first time in Korea, a 30kVA superconducting generator has been designed, developed and successfully tested recently. This is the forerunner of a 1MVA superconducting generator which is currently under development. The paper discusses the structure and manufacturing of a superconducting generator. Helium transfer coupling has 3 passages of the recovered Helium gas and a gas flow control system.