• Title, Summary, Keyword: AC insulation breakdown

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Electrical AC Insulation Breakdown Characteristics of Various Epoxy / Heterogeneous Inorganic Mixed Composite (여러 종류의 에폭시/이종무기물 혼합 콤포지트의 전기적 교류 절연파괴 특성)

  • Park, Jae-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.11
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    • pp.1463-1470
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    • 2018
  • In this study, 20 types of samples were prepared by mixing different kinds of inorganic materials to develop insulation materials for epoxy - based GIS substation equipment used under high voltage environmentally friendly insulation gas. One of the electrical characteristics, AC insulation breakdown experiment was performed. As mixing ratio of mixed heterogeneous inorganic materials, the dielectric breakdown strength was increased with increasing filler ratio of micro silica, micro silica : micro Alumina, 1:9, 3:7, 5:5, 7:3, 9:1, and decreased as the filling amount of micro alumina increased. The AC insulation breakdown characteristics were the best when the composition ratio was 9:1. The higher the content of silica, the better the interfacial properties, and the larger the alumina content ratio, the worse the interfacial properties.

Analysis of Insulation Condition in Traction Motor Stator Windings (견인전동기 고정자 권선의 절연상태 분석)

  • Kim, Hee-Dong;Park, Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.7
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    • pp.631-635
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    • 2007
  • Diagnostic, surge and ac breakdown tests are widely used to evaluate the insulation condition of stator winding in traction motor. Diagnostic test included ac current, tan delta and maximum partial discharge. The result of diagnostic test indicates that five kinds of stator windings are good condition. Surge test was peformed to confirm the healthy of turn insulation in stator windings. This test is very easy to detect the turn insulation failure between normal and defect stator windings. After completing the diagnostic test, ac breakdown test has conducted gradually increasing ac voltage, until the stator winding punctured. No. 5 stator windings failed near rated voltage of 18.9 kV The breakdown voltage of No. 1 stator windings was 13.0 kV The ac breakdown voltage of normal winding is about 1.45 times higher than that of defect windings. The failure was located in a line-end coil at the exit from the core slot.

Accelerated Insulation Life Estimation for PAI/Nano Silica Enamelled Wire under Inverter Surge and Temperature Stress (인버터 서지와 온도스트레스 하에서 PAI/Nano Silica 에나멜와이어의 가속절연수명 평가)

  • Park, Jae-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.10
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    • pp.1712-1720
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    • 2016
  • AC and DC insulation breakdown voltage was studied for magnet wire coated with double layers of high flexural PAI layer and high anti-corona PAI/nanosilica (15 wt%) layer. The specimens were prepared at various drying temperatures (T/D): $22^{\circ}C$, $240^{\circ}C$, and $260^{\circ}C$, respectively. The increase effects of nanosilica on AC and DC insulation breakdown voltage were not so significant compared to that of magnet wire coil coated with original PAI. And the AC and DC insulation breakdown voltage was improved by decreasing diameter of winding coil. As T/D temperature increased, AC and DC insulation breakdown voltage decreased.

Characteristics of Insulation Diagnosis and Failure in Gas Turbine Generator Stator Windings

  • Kim, Hee-Dong
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.280-285
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    • 2014
  • In order to evaluate the insulation deterioration in the stator windings of five gas turbine generators(137 MVA, 13.8 kV) which has been operated for more than 13 years, diagnostic test and AC dielectric breakdown test were performed at phases A, B and C. These tests included measurements of AC current, dissipation factor, partial discharge (PD) magnitude and capacitance. ${\Delta}I$ and ${\Delta}tan{\delta}$ in all three phases (A, B and C) of No. 1 generator stator windings showed that they were in good condition but PD magnitude indicated marginally serviceable and bad level to the insulation condition. Overall analysis of the results suggested that the generator stator windings were indicated serious insulation deterioration and patterns of the PD in all three phases were analyzed to be internal, slot and spark discharges. After the diagnostic test, an AC overvoltage test was performed by gradually increasing the voltage applied to the generator stator windings until electrical insulation failure occurred, in order to determine the breakdown voltage. The breakdown voltage at phases A, B and C of No. 1 generator stator windings failed at 28.0 kV, 17.9 kV, and 21.3 kV, respectively. The breakdown voltage was lower than that expected for good-quality windings (28.6 kV) in a 13.8kV class generator. In the AC dielectric breakdown and diagnostic tests, there was a strong correlation between the breakdown voltage and the voltage at which charging current increases abruptly ($P_{i1}$, $P_{i2}$).

Correlation between Insulation Diagnostic Test and AC Breakdown Test for 3.3 kV Class Induction Motor

  • Byun, Doo-Gyoon;Hong, Jin-Woong
    • Transactions on Electrical and Electronic Materials
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    • v.7 no.5
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    • pp.262-266
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    • 2006
  • The insulation diagnostic test and the AC breakdown test were performed under off-line using the 3.3 kV class induction motor which have been served for 10 years. These tests were conducted in means of nondestructive and destructive test. In this paper, we compared the correlation between the nondestructive and destructive test. Furthermore we setup an experimental condition with moisture and compared the insulation characteristics between moist and dry sample. From the results of the nondestructive and destructive test, it was found that the second AC current, which is the previous step of insulation breakdown, suddenly increased at a point of around 8.5 kV. The insulation breakdown of moist sample occurred at 12-14 kV, which is 4-5 kV lower than dry sample.

Properties of EMNC According to Addition Contents Variation for Nanosilica (2) -For Mechanical, Electrical Properties (나노 실리카 충진함량 변화에 따른 EMNC의 특성 연구 (2) -기계적, 전기적 특성 중심으로-)

  • Park, Jae-Jun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.25 no.11
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    • pp.886-894
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    • 2012
  • In order to develop electrical insulation materials, epoxy-nanosilica-microsilica mixture composites (ENMC) was synthesized, and mechanical properties such as their tensile and flexural strength, and AC insulation breakdown strength were investigated. Properties of mechanical strength and AC insulation breakdown strength are analyzed as scale and shape parameter with respect to weibull plot. Their tensile and flexural strength, AC insulation breakdown strength were compared original epoxy or EMC to ENMC. The 4 phr nano-silica addition and the 65 wt% micron-silica mixture composite (ENMC) was found to have the highest tensile and flexural strength. In the tensile strength was improved 29%, and flexural strength was improved 60.9% higher than those of the original epoxy. In the insulation breakdown strength, ENMC_4 phr was improved 17% and ENMC_5 phr was improved 15.8% higher than those of the EMC.

A Study on Mechanical, Electrical Properties of Epoxy/MICA Composites with MICA Filled Contents (Epoxy/MICA 복합체의 MICA 충진함량 변화에 대한 기계적, 전기적 특성연구)

  • Park, Jae-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.2
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    • pp.219-227
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    • 2013
  • This paper reported a study on the thermal, mechanical and electrical insulation properties of epoxy/mica composites. To investigate the effect of mica content, glass transition temperature, mechanical properties such as tensile and flexural strength, and insulation breakdown properties for epoxy composites with various contents of mica. The effect of insulation thickness on insulation breakdown property was also studied. It was observed that tensile and flexural strength decreased with increasing mica content, while elastic modulus increased as the mica content increased. AC insulation breakdown strength for all epoxy/mica composites was higher than that of neat epoxy and that of the system with 20 wt% mica was 14.4% improved. As was expected, insulation breakdown strength at $30^{\circ}C$ was far higher than that at $130^{\circ}C$, and it was also found that insulation breakdown strength was inversely proportion to insulation thickness.

AC Breakdown Analysis by Epoxy Thickness in Composite-Insulation (복합절연물내의 에폭시 두께에 따른 AC 절연파괴 분석)

  • Jung, Hae-Eun;Yun, Jae-Hun;Kim, Byoung-Chul;Kang, Seong-Hwa;Lim, Kee-Joe
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.468-469
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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. As one of the study for $SF_6$ free technology, composite-insulation technology is focused in this paper. To analyze the influence by epoxy thickness change, the composite-insulation composed of dry-air and epoxy was used in this paper. To analyze AC breakdown by the epoxy thickness, needle-plane electrode was used and needle was molded by epoxy. 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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The AC Insulation Breakdown Properties of Epoxy/Multi-Alumina Composites for Adding Surface Modified Nano Alumina (표면처리된 나노알루미나가 첨가된 에폭시/멀티-알루미나 콤포지트의 교류절연파괴 특성)

  • Park, Jae-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.9
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    • pp.1511-1517
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    • 2016
  • The aim of this study is to improve of properties for electrical AC insulation breakdown strength using epoxy/micro-nano alumina composites with adding glycerol diglycidyl ether (GDE:1,3,5g). This paper deals with the effects of GDE addition for epoxy/micro alumina contents (40,50,60wt%)+surface modified nano alumina(1_phr) composites. 14 kinds specimen were prepared with containing epoxy resins, epoxy micro composites and epoxy nano-micro alumina mixture composites. Average particle size of nano and micro alumina used were 30nm and $1{\sim}2{\mu}m$, respectively. The micro alumina used were alpha phase with Heterogeneous and nano alumina were gamma phase particles of spherical shape. The electrical AC insulation breakdown strength was evaluated by sphere to sphere electrode system and raising velocity 1kV/s. The AC breakdown strength decreased insulation properties of multi-composites according to increasing micro alumina and GDE addition contents.

Analysis of AC Breakdown Voltage of Composite Insulation for Dry-Air/Epoxy (건조공기/에폭시 복합절연물의 AC 파괴전압 분석)

  • Heo, Jun;Lee, Seung-Su;Lim, Kee-Joe;Jung, Hae-Eun;Kang, Seong-Hwa
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.289-290
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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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