• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.11
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• pp.556-562
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• 2001

Spacer is used between main tank and auxiliary tank for on load tap changer in gas insulated power transformer. This paper deals with electrical design of spacer and discusses different analysis method of between 2D FEM(finite element method) and 3D FEM. To design spacer, we modeled structure of two kind of coaxial cylinders of spacer conductors and analysised electric field of spacer at impulse and induced test voltage condition. Spacer has 13 conductors and electric field was changed according to arrangement of conductors. We could find out arrangement of conductors at which electric stress is minimum. And this arrangement was satisfied with actual test conditions.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.106-108
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• 2002

Capacitive current switching test for circuit breaker and load breaker switch requires special attention because, after current interruption, the capacitive load contains an electrical charge and can cause dielectric restrike and re-ignition of the switching devices. therefore dielectric strength of capacitor load bank shall be able to withstand 4Vt (Vt : test voltage) and charging voltage discharged within 1 min. In this paper presents both characteristic of capacitive current switching tests and design of capacitor load bank.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.572-573
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• 2012

전력 수요 급증과 전력 기술 발전으로 인해, 오늘날 HVDC 기술이 널리 사용되고 있다. 또한 지구 온난화, 녹색 에너지 개발, 스마트 그리드 사업 등으로 인해 세계적으로 HVDC 수요가 급증하고 있는 추세이다. 국내에서도 제주-해남간 HVDC 1호기가 이미 운영 중에 있으며, 제주-진도간 HVDC 2호기가 2012년 완공을 목표로 현재 설치 중에 있다. 2009년 HVDC 사업에 진출한 LS산전은 지난해 변환용 변압기를 국내 최초로 생산한데 이어, HVDC 핵심 요소인 싸이리스터 밸브(thyristor valve)도 개발 완료 하였다. 싸이리스터 밸브는 HVDC 시스템의 변환설비 중 심장 역할을 하는 핵심적인 설비로 교류를 직류로, 또는 직류를 교류로 변환시켜 교류 계통에 전력을 공급하는 장치로, 사용하기 전에 성능을 충분히 검증해야 한다. LS산전은 독자적으로 개발한 싸이리스터 밸브를 IEC 규격에 따라 엄격히 시험하여 성능을 입증하였다. 본 논문에서는 개발 시험의 일부로 수행한 싸이리스터 밸브에 대한 절연 시험(dielectric test)를 소개하고자 한다.

• Polymer(Korea)
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• v.33 no.1
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• pp.39-44
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• 2009

Polymer substrates were fabricated by using poly (phenylene ether) as a base resin, N,N'-m-phenylenedimaleimide (PDMI) as a crosslinking agent and decabromodiphenylethane as a flame retardant. The effects of crosslinking agent and flame retardant on physical properties such as dielectric property of the substrate were investigated. Thermal curing feature of PDMI with or without an initiator was analyzed by DSC, and then, PPE-PDMI test compositions were designed based on this result. Composite sheets were cast by film coater, laminated under vacuum and pressure, and then, the changes of dielectric constant, dielectric loss, peel strength, solder heat resistance and inflammability according to increasing amount of PDMI and flame retardant were evaluated, Dielectric constant and dielectric loss showed increasing trend with increasing amount of PDMI and flame retardant, but solder heat resistance and inflammability were improved. Peel strength was obtained higher than 1 kN/m when PDMI above 10 wt% was added, but slightly decreased as the amount of flame retardant increased. From the measured gel contents, the reaction mechanism of PPE-PDMI system was deduced to the formation of network structure by crosslinking PDMI with PPE rather than the formation of semi-IPN structure. In conclusion, the polymer composite substrate materials with dielectric constant of 2.52$\sim$2.65 and dielectric loss below 0.002 at 1 GHz were obtained and they will be proper for high frequency applications.

• Journal of the Korean Ceramic Society
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• v.43 no.2 s.285
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• pp.92-97
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• 2006

Dolomite type $BaSn(BO_3)_2$ ceramics with rhombohedral crystal structure has been synthesized via solid state reaction route. Dielectric properties were measured for the samples sintered at $1050\~1200^{\circ}C$ for 2 h in air. Dielectric constant, loss tangent, and temperature coefficient were increased with sintering temperature due to the evolution of $BaSnO_3$, secondary, phase. Optimum dielectric properties were obtained at the $BaSn(BO_3)_2$ ceramics sintered at $1100^{\circ}C.\;CuO/Bi_2O_3$ was added to $BaSn(BO_3)_2$ ceramics to lower the sintering temperature for LTCC application, then Co and Fe-based coloring agents were added for colorizing the LTCC tape. Typical dielectric properties of $BaSn(BO_3)_2$ ceramics with $5 wt\%\;CuO/Bi_2O_3\;and\;3wt\%$ Co-coloring agent that sintered at $900^{\circ}C$ were $\varepsilon_r=9.89,\;tan{\delta}=0.92\times10^{-3},\;and\;TCC=112ppm/^{\circ}C$. Thus obtained LTCC tape was co-fired with Ag paste for compatibility test and revealed no sign of Ag reaction with the ceramics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.936-942
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• 2009

This paper presents the delivered power and reflection coefficient in metallic shielding enclosure with a sub-cavity, which are evaluated with the method of moments, sad describes a method for controlling the resonance characteristics of the metallic cavity by putting lossy dielectric material in the sub-cavity. In this paper we introduce carbon polystyrene-foam as lossy dielectric material and observe it's effects of reduction when the dimensions of the sub-cavity and permittivity of lossy dielectric material are changed. The results show that the reduction of the electromagnetic radiation can be achieved by controlling the amount of carbon in lossy dielectric material and the dimensions of the sub-cavity. The theoretical analysis is verified by the measured delivered power.

• Journal of the Korean Ceramic Society
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• v.43 no.1 s.284
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• pp.55-61
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• 2006

The microwave dielectric properties and low temperature sintering of $Ca[Ti_{1-x}(Ni_{1/3}Nb_{2/3})_x]O_3$ system were investigated at the sintering temperature $1,200\~1,350^{\circ}C$. The density and quality factors $(Q{\times}f)$ increased while dielectric constants slightly decreased with the decrease of Ti. The dielectric constant, quality factor, and temperature coefficient of resonance frequency $(\tau_f)$ were 64, 17,000 GHz, and $-9.1\;ppm/^{\circ}C$ respectively, when $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ ceramics were sintered at $1,300^{\circ}C$ for 4 h. $2Li_2O-B_2O_3$ was added to $CaTi_{1/2}(Ni_{1/3}Nb_{2/3})_{1/2}O_3$ to decrease the sintering temperature for LTCC application. The microwave dielectric properties of the samples sintered at $925^{\circ}C$ for 2 h with the addition of $6\;wt\%\;2Li_2O-B_2O_3$ were $\varepsilon_r=48.7,\;Q{\times}f=8,460\;GHz$, and $\tau_f=+5.6ppm/^{\circ}C$. Compatibility test of the composition with silver electrode shows no reaction with silver electrode, implying the feasibility as a high-K LTCC material.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.3
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• pp.56-63
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• 2003

A silent type ozone generator using water surface has been studied and improved its ozone generation characteristics by installing dielectric heads in the just under the surface of the wale- At this time, different permittivitis of dielectric beads were used to change the discharge condition of water surface. The current-voltage characteristics and characteristics of ozone generation quantity of the test system were investigated and discharge photos of glass beads were observed The height of Taylor cone may be the cause of the discharge bridge to decrease the ozone generation on the discharge spacing. In this study, the hight of Taylor cone could be controlled greatly by installing dielectric beads just under the water surface. Therefore a higher ozone generation also could be obtained. As the permittivity of dielectric material increased. discharge starting voltage was advanced and maximum 110 ppmy of ozone was generated by using the ferroelectric ball.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1087-1094
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• 2010

We have developed a cylindrical multi-terminal capacitive-conductive sensor that could be attached to the internal surface of cooling system pipe to evaluate capacitance and conductivity of heat transfer fluid. It was used as measuring system to diagnose insulating condition, by which was kept a insulating resistance of inner stack and at the same time was cooled electrochemical heat of reaction of FCEV(fuel cell electric vehicle) stack that used a compressed hydrogen gas reacting with oxygen in accordance with variation on thermal degradation of nonconductive heat transfer fluid. Also to assess diagnosis characteristics of heat transfer fluid, i.e. coolant, we have performed accelerated aging test using developed sensor attached to cooling system. Consequently, it was measured dielectric and electric resistance of coolant to estimate and analyse for dielectric properties by degradation condition.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.147-150
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• 1988

Since the integration level of VLSI circuits progresses very quickly, a highly reliable thin $SiO_2$ film is required to fabricate a small-geometry MOS device. In the present study we have attempted to eliminate the failure-causing defects that develop in thin oxide films during the oxidation step by performing a long-time preoxidation and postoxidation annealing. The TDDB test and the copper decoration method were used to calculate the oxide defects density of MOS device. The dielectric reliability of high-quality thin oxides have been studied by using the time-zero-dielectric-breakdown (ramp-voltage-stressed I-V) and time-dependent-dielectric -breakdown (Constant-stressed I-V) tests. Failure times against temperature and electric field are examined and acceleration factors are abtained for each parameter. Based on the data obtained, breakdown wearout limitation for thin oxide films is estimated.