• Title/Summary/Keyword: AC electric field

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Properties of EMNC and EMNSC for Insulation New Material as Apply to High Voltage Heavy Electric Machine (고압중전기기용 절연신소재 EMNC와 EMNSC의 특성연구)

  • Park, Jae-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.10
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    • pp.1454-1460
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    • 2012
  • In order to develop an new electric insulation material for heavy electric equipments, epoxy/micro/nano composite (EMNC) was prepared by mixing micro-silica with nano layered silicate, where the nano layered silicate was synthesized by our electric field dispersion method, EMNSC was prepared by treating the EMNC with a silane coupling agent. Thermal properties such as glass transition temperature (Tg) and thermal expansion coefficient, and DMA characteristics were studied, and mechanicla properties such as tensile and flexural tests were performed. AC electrical insulation strength was also tested. All properties of EMNSC were modified by treating EMNC with silane coupling agent and it was confirmed that our new developed composites could be used in the heavy electric equipments.

Space Charge Measurement as a Diagnostic Tool to Monitor Ageing in Polymeric Materials

  • Chen, George
    • Transactions on Electrical and Electronic Materials
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    • v.7 no.5
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    • pp.235-239
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    • 2006
  • Charge dynamics in polymeric materials after aged under ac electric field using the pulsed electroacoustic (PEA) technique is reported. The emphasis is placed on charge decay. The charge dynamics of the ac aged additive free low density polyethylene (LDPE) samples under dc bias differ from the sample without ac ageing, indicating changes brought in by ac ageing. It is believed that a slow decay rate of charge in the ac aged sample is related to the formation of deep traps in the material. However, chemical analysis by infrared spectroscope (FTIR) and Raman microscope reveals no significant chemical changes taken place in the bulk of the material after ac ageing. Further experiments on irradiated LDPE have revealed a similar behaviour, i.e. the charge decay is slower in irradiated samples than that of fresh sample. The findings presented clearly indicate that space charge measurement can be used as a diagnostic tool to monitor ageing in polymeric materials.

AC Loss Characteristic Analysis of Superconducting Power Cable for High Capacity Power Transmission (대용량 전력 전송을 위한 초전도 전력케이블의 교류손실 특성 분석)

  • Lee, Seok-Ju
    • Journal of Korea Society of Industrial Information Systems
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    • v.24 no.2
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    • pp.57-63
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    • 2019
  • In order to facilitate the supply of gradually increasing power demand, it is also necessary to increase the number of power cables for power transmission as well as generation facilities. However, the expansion of electric power cables for supplying power to most urban areas requires a space for installation of additional cables, and the space for installing cables in domestic downtown areas is insufficient at present. The superconducting power cable, which can transmit more power with the same size, has emerged as an alternative to overcome the insufficient cable installation space. However, superconducting power cables, which have the advantage of large power transmission, have some losses in the AC (Alternating Current) system. Therefore, the design and analysis of AC losses are essential to introduce superconducting power cables in AC power transmission systems. In this paper, we analyze the AC loss of various superconducting power cables and consider the actual superconducting power cables and their application to the system. Although there is a theoretical calculation method of AC loss for single superconducting wire, it is not easy to calculate AC loss of superconducting power cable with large number. Therefore, the authors intend to analyze various kinds of superconducting power cable AC loss by using electromagnetic finite element analysis considering E-J (Electric field-Current density) characteristics of superconductivity. The analysis of the AC loss characteristics of the superconducting power cable will be an important factor in the design and development of the superconducting power cable to be applied to the actual system.

A survey on the EMF Levels of Study and Electric Appliances in Korea (국내 전철 및 가전제품을 대상으로 한 전자장 수준 실태조사)

  • Jang, Seong Ki;Cho, Yong Sung;Lee, Seok Jo;Yoo, Seong Wha;Jung, Kyung Mi;Lim, Jun Ho
    • Journal of Korean Society of Occupational and Environmental Hygiene
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    • v.15 no.1
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    • pp.71-81
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    • 2005
  • The purposes of this study was to collect, analyze, and describe the MF exposure levels from subways in Korea and to measure and evaluate the MF levels generated from electric appliances used at general homes. The target subway lines were Seoul Metropolitan Line 1 to Line 8, Bundang Line, Incheon Line, Daegu Line, Gwangju Line, and Busan Line 1 and Line 2. We measured at each station in those subway lines and, all the train types (pantograph-equipped, motor-equipped, and common), and platform types(facing and isolating) were investigated by the distance(80, 200, 400 cm) from the train on 19 targeted subway lines using 3 magnetic field measuring devices (EMDEXII, Enertech Co.) during the survey from January till October, 2004. On the other hand, the levels of the 60Hz magnetic fields generated from 14 items of home electric appliances such as electric blankets, hair dryers, electric razors, etc. were measured at 10 general homes using 5 EMDEXII meters with a sampling interval of 1.5 second by the distance(surface, 30, 50, 100, 300cm ) from the target electric appliances. The survey results in the whole subway lines examined in this study were as follows; Seoul Metropolitan Line 4 using AC(alternating current) power source showed the highest mean value of $2.85{\mu}T$, followed by Seoul Metropolitan Line 1 running between Seoul and Incheon using AC($2.78{\mu}T$), Seoul Metropolitan Line 1 between Seoul and Uijongbu using AC($2.73{\mu}T$), Bundang Line using AC($1.79{\mu}T$), Seoul Metropolitan Line 1 connected from Yongsan using AC($1.67{\mu}T$), Seoul Metropolitan Line 1 between Seoul and Suwon using AC($0.79{\mu}T$), and so on. In general, the intensity of the magnetic field in the subway systems in Korea was significantly higher when using AC($2.14{\pm}0.91{\mu}T$) than when using DC($0.29{\pm}0.44{\mu}T$) power source. Among the home electric appliances examined, microwave ovens showed the highest mean value of $7.69{\mu}T$, followed by hair dryers($6.47{\mu}T$), vacuum cleaners($5.27{\mu}T$), televisions ($2.26{\mu}T$), electric blankets($1.38{\mu}T$), personal computers ($0.81{\mu}T$), and so on. Two items of electric appliances showed the excess value of $0.2{\mu}T$ at the distance of 30cm in the MF exposure level; electric razors $1.58{\pm}2.13{\mu}T$ and vacuum cleaners $0.48{\pm}0.44{\mu}T$. As a whole, this study showed a tendency that the shift of the MF levels according to the increase of distance from the electric appliances was lower than those of the results surveyed in UK and USA. As a result, this study is expected to suggest meaningful data for the future study in exposure assessment of magnetic fields and for the establishment of guidelines for subways and electric appliances in Korea. More detailed and large scaled exposure assessment studies should be performed continuously to get the various and useful information on health risk assessment of MFs in Korea.

Patent map development of High-efficiency electric machineries (고효율 전기기기 특허동향 분석)

  • 박종진;이창호;김남정
    • Proceedings of the Korea Technology Innovation Society Conference
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    • 2000.11a
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    • pp.177-193
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    • 2000
  • In foreign countries, high-efficiency electric machineries have been developed in view of cost reduction, environmental issues, energy conservation etc. Especially they focus on developing energy conservation measures and demand-side management. Thus, patent application and secure of patent claims are on the rise as important issues in this field. In this paper, we analyzed patent application trends about inverters, ac/dc converters, reactive power control equipments, high-efficiency transformers and electric ballasts among high-efficiency electric machineries. First, we analyzed general technology trends, and constructed patent technology data. Second, we graphed patent application trends in terms of application years, assignees and nations.

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A High Performance AC Propulsion System for Electric Car (전동차용 고성능 AC구동시스템의 개발)

  • Jung, K.C.;Bang, L.S.;Kim, D.S.;Seo, K.D.;Kim, N.H.
    • Proceedings of the KIEE Conference
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    • 1996.07a
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    • pp.278-280
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    • 1996
  • This paper presents a high performance AC propulsion system for electric car to improve traction capability. The presented VVVF inverter was composed of as GTO thyristor and the the controller was fully digitalized by using 32bit DSP. The improved PWM algorithms and the new adhesion control were adapted to improve traction characteristics. This system could be possible the higher reliability and flexibility. The field test results showed the higher performances characteristics of the presented system.

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Analysis of AC Breakdown Voltage accoding to epoxy thickness of Composite Insulation for Dry-Air/Epoxy under non-uniform electric field (불평등전계에서의 건조공기/에폭시 복합절연물의 에폭시 두께에 따른 AC 파괴전압 분석)

  • Heo, Jun;Lee, Seung-Su;Lim, Kee-Joe;Jung, Hae-Eun;Kang, Seong-Hwa
    • Proceedings of the KIEE Conference
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    • 2008.10a
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    • pp.113-114
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    • 2008
  • The purpose of this paper is to analyze AC Breakdown of solid/air composite insulation depending on the thickness and the pressure of dry air for eco-friendly insulation. SF6 gas has been widely used in electric equipment as gas insulation because of high dielectric strength and arc extinguishing performance. However, because SF6 gas is one of the green house effect gases, alternative insulation such as SF6 mixture, extremely low temperature gas, vacuum, liquid and solid insulating are being investigated.

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The Characteristics of Frequency Spectrum of Radiated Electromagnetic Waves with AC Discharge Progress in Liquid Nitrogen (액체 질소중 교류방전 진전에 따른 방사전자파의 주파수 스펙트럼 특성)

  • 박광서;윤대희;이상훈;이현동;김충년;최병주;김기채;이광식
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.52 no.3
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    • pp.123-129
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    • 2003
  • In this paper, a relationship between AC discharge progress and the radiated electromagnetic waves was investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The frequency spectrum of the radiated electromagnetic waves were measured at the atmospheric pressure in liquid nitrogen($LN_2$) during partial discharges progressed by AC high voltage in nonuniform electric field. Front the results of this study, a new method was introduced for measurement and analysis of the radiated electromagnetic waves with discharge progress in $LN_2$ Besides. according to the consideration of the mutual relation between frequency spectrum of the radiated electromagnetic waves and discharge progress, it was confirmed that detecting partial discharge and estimating discharge progress could be possible. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of electric insulations about superconducting and cryogenic power equipments.

AC Breakdown Analysis of Composite-Insulation by the Thickness of epoxy and the Variation of Pressure (복합절연물내 기체의 압력 및 고체의 두께변화가 AC 절연파괴에 미치는 영향 분석)

  • Jung, Hae-Eun;Kim, Byoung-Chul;Yun, Jae-Hun;Kang, Seong-Hwa;Lim, Kee-Joe
    • Proceedings of the KIEE Conference
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    • 2007.11a
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    • pp.194-195
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    • 2007
  • $SF_6$ gas used widely as insulating component in electric power industry has excellent in insulation and arc extinguishing performance in gas-insulated switchgear. However, the concern about eco-friendly alternative gas is currently rising because $SF_6$ gas is one of the main greenhouse gases. In this paper, dry-air and composite-insulation (dry-air+epoxy) as the alternative technology for $SF_6$ gas insulation is studied. Under the gas pressure ranged from 0.1 to 0.6MPa, the breakdown voltage of dry-air were measured in AC electric field. The data of composite-insulation were acquired by changing the thickness of epoxy used in each composite-insulation under the same condition.

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Research for Installation and Operation of High Temperature Superconducting Cable System (고온 초전도 케이블 시스템 설치 밀 운전을 위한 연구)

  • Choi, Hyung-Sik;Sohn, Song-Ho;Hwang, Si-Dole
    • Proceedings of the KIEE Conference
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    • 2005.07a
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    • pp.653-657
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    • 2005
  • The commercial contract was made firstly in the world for one set of high temperature superconducting(HTS) cable system between buyer, Korea Electric Power Research Institute and seller, Sumitomo Electric Industries, Ltd. in August 2004. After fabrication, test and examination, the HTS cable system will be installed at the KEPRI's test field in Gochang, Jeonbuk province from the time of July 2005. KEPRI is preparing measurement and test facilities for field test of the HTS cable system and carrying out researches into the design and construction of superconducting cable test building, evaluation of cooling performance, measurement of AC loss, analysis of the quench phenomena due to excess current and means of linking the HTS cable system to the existing electric power supplying system. The constitution of, the method to install and the plan of test operation of the HTS cable system will be presented in this paper.

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