• Title/Summary/Keyword: Dielectric strength

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Estimation of Insulation Diagnosis and Dielectric Strength in 6.6 kV Motor Stator Windings (6.6 kV 전동기 고정자 권선의 절연진단과 절연내력 평가)

  • Kim, Hee-Dong;Kong, Tae-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.6
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    • pp.780-785
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    • 2014
  • To assess the deterioration condition of stator insulation, diagnostic and AC dielectric strength tests were performed on five high voltage (HV) motors (2,000 HP, 6.6 kV) for boiler feed-water pump (BFP). Two HV motors for BFP were installed per unit. Following the long term rewinding program, the diagnostic test was performed on five 6.6 kV motors during the planning maintenance period. After completing diagnostic test, AC dielectric strength test was done on the stator windings of HV motors. The AC dielectric strength test was conducted at 15 kV for one minute. Dielectric strength test and diagnostics test results confirmed that the stator insulation was judged to be in serviceable condition in the five 6.6 kV motors.

A Study on the Dielectric Strength of Composite Materials(I) (복합재료의 전기적 절연특성과 개발에 관한 연구(I))

  • 정은식;강창남;박정후
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.34 no.8
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    • pp.323-330
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    • 1985
  • Dielectric loss tangent and ac dielectric strength of GFRP (Glass Fiber Reinforced Plastics, G-10)was investigated as parameters of mechanical and thermal stresses, in order to study the basic dielectrical characteristics of composite insulating materials. The dielectric loss tangent was increased and the ac dielectric strength was decreased with increase in the mechanical stresses beyond the mechanical yield point on account of fiber-matrix debonding, but the dielectric constant was not varied sigificantly. the dielectric strength of G-10 was about 2 MV/cm and the dielectric constant was about 4.8.

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Dielectric Strength of Macro Interface between Epoxy and Rubber According to the Interface Condition (계면조건에 따른 에폭시와 고무 거시계면의 절연내력)

  • Oh, Yong-Cheul;Bae, Duck-Kweon;Kim, Jin-Sa;Kim, Chung-Hyeok
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.12
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    • pp.581-585
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    • 2006
  • Macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably in the complex insulation system using in extra high voltage (EHV) electric devices. In this paper, Interface between epoxy and ethylene propylene diene terpolymer (EPDM) was selected as an interface in electrical insulation system and the AC dielectric strength of the interface was investigated. Air compress system was used to give pressure to the interface. Specimens were prepared in various ways to generate different surface conditions for each type of interface. Increasing interfacial pressure, decreasing surface roughness and spreading oil over surfaces improve the AC interfacial dielectric strength. Especially, the dielectric strength was saturated at certain interfacial pressure.

A Study on Dielectric Strength and Insulation Properly of PDMS (실리콘 폴리머의 내전압 및 절연특성에 관한 연구)

  • 지원영
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.11
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    • pp.941-946
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    • 2001
  • The fundamental study on HTV silicone for insulation material has been performed. In order to estimate the chemical behavior of siloxane under high voltage, H-NMR, GPC and vinyl contents measurement were used. As an experimental results, after high voltage stress, the molecular weight of siloxane are increased, the vinyl contents of siloxane are decreased. The dielectric strength of vinyl group containing siloxane was lower than only methyl containing siloxane.

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Study on the V-t Characteristics of the Interface between Epoxy and Rubber According to the Condition of Surfaces (표면조건에 따른 에폭시/고무 계면의 V-t 특성에 관한 연구)

  • Bae, Duck-Kweon;Kim, Chung-Hyeok;Oh, Yong-Cheul;Kim, Jin-Sa;Shin, Cheol-Gee;Lee, Sung-Ill
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.11a
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    • pp.174-175
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    • 2006
  • In this paper, AC dielectric strength of the interface between Epoxy and EPDM (ethylene propylene diene terpolymer) was investigated. Air compress system was used to give pressure to the interface. Specimens were prepared in various ways to generate different surface conditions for each type of interface. Increasing interfacial pressure, decreasing surface roughness and spreading oil over surfaces improve the AC interfacial dielectric strength. Especially, the dielectric strength was saturated at certain interfacial pressure.

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공기-절연유복합유도체의 절연파괴현상에 관하여 1

  • Chul Je Cho
    • 전기의세계
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    • v.23 no.3
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    • pp.60-66
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    • 1974
  • This paper is to study on the phenomena that the compound dielectric strength through double layers of air-insulating oil dielectrics is much lower than that of air dielectrics only. the change of the dielectric strength by the variance of air gap depends on the characteristics of air gap discharge and, in case of commercial voltage, the degree of dependance is greeter than in case of direct current voltage.

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Hysteresis-free organic field-effect transistors with ahigh dielectric strength cross-linked polyacrylate copolymer gate insulator

  • Xu, Wentao;Lim, Sang-Hoon;Rhee, Shi-Woo
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2009.11a
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    • pp.48.1-48.1
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    • 2009
  • Performance of organic field-effect transistors (OFETs) with various temperature-cured polyacrylate(PA) copolymer as a gate insulator was studied. The PA thin film, which was cured at an optimized temperature, showed high dielectric strength (>7 MV/cm), low leakage current density ($5{\times}10^{-9}\;A/cm^2$ at 1 MV/cm) and enabled negligible hysteresis in MIS capacitor and OFET. A field-effect mobility of ${\sim}0.6\;cm^2/V\;s$, on/off current ratio (Ion/Ioff) of ${\sim}10^5$ and inverse subthreshold slope (SS) as low as 1.22 V/decwere achieved. The high dielectric strength made it possible to scale down the thickness of dielectric, and low-voltage operation of -5 V was successfully realized. The chemical changes were monitored by FT-IR. The morphology and microstructure of the pentacene layer grown on PA dielectrics were also investigated and correlated with OFET device performance.

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The Estimation of the Dielectric Strength Decrease of the Solid-solid Interfaces by using the Applied Voltage to Breakdown Time Characteristics

  • Shin, Cheol-Gi;Bae, Duck-Kweon
    • Transactions on Electrical and Electronic Materials
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    • v.8 no.6
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    • pp.278-282
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    • 2007
  • In the complex insulation system that is used in extra high voltage(EHV) devices, according to the trend for electric power equipment of high capacity and reduction of its size, macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably. In this paper, the dielectric strength decrease of the macro interfaces between epoxy and ethylene propylene diene terpolymer(EPDM) was estimated by using the applied voltage to breakdown time characteristics. Firstly, the AC short time dielectric strength of specimens was measured at room temperature. Then, the breakdown time was measured under the applied constant voltage which is 70% of short time breakdown voltage. With these processes, the life exponent n was determined by inverse power law, and the long time breakdown voltage can be evaluated. The best condition of the interface was LOS(low viscosity(350 cSt) silicone oil spread specimen). When 30 years last on the specimens, the breakdown voltage was estimated 44% of the short time breakdown voltage.

Dielectric Strength for Imitation Air with Pressure Variation under Uniform and Non-Uniform Fields (평등/불평등 전계하의 제조공기(I-Air)에 대한 압력별 절연파괴강도 특성)

  • Lee, Chang-Uk;Lee, Chang-Hun;Choi, Eun-Hyuck;Lee, Sang-Ho;Lee, Kwang-Sik
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2007.11a
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    • pp.263-266
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    • 2007
  • In this paper approves (AC and DC) high voltage by experimental GIS(Gas Insulated Switchgear) chamber and (AC and DC) power source to study breakdown characteristics by pressure(P) change and change of electrode distance(d) at (AC and DC) high voltage of Imitation I-Air, $N_2$ : $O_2$ = 79(%) : 21[%]) to alternate $SF_6$ and achieved research. Gave P change of I-Air to study I-Air's Dielectric Strength using uniform and non-uniform fields(sphere-sphere and Needle-Plane electrode) and studied relations dielectric strength($V_D$) by each P different d.

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A Research on Dielectric Characteristics of Small Current Interruption Considering Pre-Condition Test for Puffer Type Circuit Breaker (Pre-Condition 시험을 고려한 Puffer식 차단기의 진상소전류 차단성능에 관한 연구)

  • Ahn, Heui-Sub;Yoon, Jeong-Hoon;Lee, Jong-Chul;Choi, Jong-Ung;Oh, Il-Sung;Lee, Sung-Ho
    • Proceedings of the KIEE Conference
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    • 2003.10b
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    • pp.12-14
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    • 2003
  • This paper presents the small current interruption capability of $SF_6$ puffer circuit breaker considering pre-condition. Firstly, the change of dielectric strength of the 3 breakers was compared with testing breakers as clean contacts and eroded contacts after 3 shots of 760 according to new IEC 62271-100 standard. Also the dielectric strength curve of each model was calculated through flow and electric field simulations. From these results, we could modify the empirical equation, being used to predict the dielectric strength of small current interruption capability, considering the effects of pre-condition.

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