• Title/Summary/Keyword: Insulation failure

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A Study on the Condition Diagnosis for A Gas-insulated Transformer using Decomposition Gas Analysis (가스분해 분석기법을 활용한 가스 전열 변압기의 상태 진단 연구)

  • Ah-Reum, Kim;Byeong Sub, Kwak;Tae-Hyun, Jun;Hyun-joo, Park
    • KEPCO Journal on Electric Power and Energy
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    • v.8 no.2
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    • pp.119-126
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    • 2022
  • A growing number of gas-insulated transformers in underground power substations in urban areas are approaching 20 years of operation, the time when failures begin to occur. It is thus essential to prevent failure through accurate condition diagnosis of the given facility. Various solid insulation materials exist inside of the transformers, and the generated decomposition gas may differ for each gas-insulated equipment. In this study, a simulation system was designed to analyze the deterioration characteristics of SF6 decomposition gas and insulation materials under the conditions of partial discharge and thermal fault for diagnosis of gas-insulated transformers. Degradation characteristics of the insulation materials was determined using an automatic viscometer and FT-IR. The analysis results showed that the pattern of decomposition gas generation under partial discharge and thermal fault was different. In particular, acetaldehyde was detected under a thermal fault in all types of insulation, but not under partial discharge or an arc condition. In addition, in the case of insulation materials, deterioration of the insulation itself rapidly progressed as the experimental temperature increased. It was confirmed that it was possible to diagnose the internal discharge or thermal fault occurrence of the transformer through the ratio and type of decomposition gas generated in the gas-insulated transformer.

Computer Vision-based Automated Adhesive Quality Inspection Model of Exterior Insulation and Finishing System (컴퓨터 비전 기반 외단열 공사의 접착제 도포품질 감리 자동화 모델)

  • Yoon, Sebeen;Kang, Mingyun;Jang, Hyounseung;Kim, Taehoon
    • Journal of the Korea Institute of Building Construction
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    • v.23 no.2
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    • pp.165-173
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    • 2023
  • This research proposed a model for automatically monitoring the quality of insulation adhesive application in external insulation construction. Upon case implementation, the area segmentation model demonstrated a 92.3% accuracy, while the area and distance calculation accuracies of the proposed model were 98.8% and 96.7%, respectively. These findings suggest that the model can effectively prevent the most common insulation defect, insulation failure, while simultaneously minimizing the need for on-site supervisory personnel during external insulation construction. This, in turn, contributes to the enhancement of the external insulation system. Moving forward, we plan to gather construction images of various external insulation methods to refine the image segmentation model's performance and develop a model capable of automatically monitoring scenarios with a considerable number of insulation materials in the image.

The Improvement on Insulation Performance of Underground Distribution Power Cables (지중배전케이블 절연성능 향상 방안)

  • Lee, Jae-Bong;Lee, Byung-Sung;Kim, Sang-Joon;Jang, Sang-Ok;Han, Yong-Huei;Oh, Jae-Hyoung
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2004.05a
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    • pp.497-501
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    • 2004
  • The primary failure causes of underground distribution power cables are water penetration in insulation layer and stress enhancement at inner semi-conductive layer. Accordingly, it is needed to improve the materials and the structure of power cables for extending lifetime and preventing failure. We uses non-flaming PE materials instead of PVC as a covering material and encapsulating structure. We also use super smooth class material as a inner semi-conductive layer. The newly developed cables are improved in AC breakdown voltage after ageing tests.

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Analysis of Thermal Characteristics and Insulation Resistance Based on the Installation Year and Accelerated Test by Electrical Socket Outlets

  • Kim, Kyung Chun;Kim, Doo Hyun;Kim, Sung Chul;Kim, Jae Ho
    • Safety and Health at Work
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    • v.11 no.4
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    • pp.405-417
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    • 2020
  • Background: Electrical socket outlets are used continuously until a failure occurs because they have no indication of manufacturing date or exchange specifications. For this reason, 659 electrical fires related to electrical socket outlets broke out in the Republic of Korea at 2018 only, an increase year on year. To reduce electrical fires from electrical socket outlets, it is necessary to perform an accelerated test and analyze the thermal, insulation resistance, and material properties of electrical socket outlets by installation years. Methods: Thermal characteristics were investigated by measured the temperature increase of electrical socket outlets classified according to year with variation of the current level. Insulation resistance characteristics was measured according to temperature for an electrical socket outlets by their years of use. Finally, to investigate the thermal and insulation resistance characteristics in relation to outlet aging, this study analyzed electrical socket outlets' conductor surface and content, insulator weight, and thermal deformation temperature. Results: Analysis showed, regarding the thermal characteristics, that electrical socket outlet temperature rose when the current value increased. Moreover, the longer the time that had elapsed since an accelerated test and installation, the higher the electrical socket outlet temperature was. With respect to the insulation resistance properties, the accelerated test (30 years) showed that insulation resistance decreased from 110 ℃. In relation to the installation year (30 years), insulation resistance decreased from 70 ℃, which is as much as 40 ℃ lower than the result found by the accelerated test. Regarding the material properties, the longer the elapsed time since installation, the rougher the surface of conductor contact point was, and cracks increased. Conclusion: The 30-year-old electrical socket outlet exceeded the allowable temperature which is 65 ℃ of the electrical contacts at 10 A, and the insulation resistance began to decrease at 70 ℃. It is necessary to manage electrical socket outlets that have been installed for a long time.

DGA Gases related to the Aging of Power Transformers for Asset Management

  • Kweon, Dongjin;Kim, Yonghyun;Park, Taesik;Kwak, Nohong;Hur, Yongho
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.372-378
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    • 2018
  • Life management technology is required as the failure risk of aged power transformers increases. Asset management technology is developed to evaluate the remaining life, establish the replacement strategies, and decide the optimal investment based on the reliability and economy of power transformers. The remaining life assessment uses data such as installation, operation, maintenance, refurbishment, and failure of power transformers. The optimal investment also uses data such as maintenance, outage, and social costs. To develop the asset management system for power transformers, determining the degradation parameters related to the aging of power transformers and evaluating the condition of power transformers using these parameters are important. In this study, since 1983, 110,000 Dissolved Gas Analysis (DGA) data have been analyzed to determine the degradation parameters related to the aging of power transformers. The alarm rates of combustible gases ($H_2$, $C_2H_2$, $C_2H_4$, $CH_4$, and $C_2H_6$), TCG, CO, and $CO_2$ were analyzed. The end of life and failure rate (bathtub curve) of power transformers were also calculated based on the failure data from 1981 to 2014. The DGA gases related to discharge, overheating, and insulation degradation were determined based on alarm and failure rates. $C_2H_2$, $C_2H_6$, and $CO_2$ were discharge, oxidation, and insulation degradation parameters related to the aging of power transformers.

Judgement Criterion of Insulation Deterioration in 4.16kV and 6.6kV Motor Stator Windings (4.16kV 및 6.6kV 전동기 고정자 권선의 절연열화 판정기준)

  • Kim, Hee-Dong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.4
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    • pp.788-794
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    • 2009
  • To assess the condition of stator insulation, nondestructive tests were performed on twenty five coil groups and twenty six motors. The stator windings has nominal ratings of 6.6kV and are classified into five coil groups ;one group with healthy insulation and four groups with four different types of artificial defects. After completing nondestructive tests, the AC voltage applied to the stator windings was gradually increasing until insulation failure in order to obtain the breakdown voltage. No.1, No.2 and No.6 of 6.6kV motors failed near rated voltage of 14kV, 8.7kV and 14kV, respectively. The breakdown voltage of three motors was lower that expected for good quality coils(14.2kV) in 6.6kV motors. No.3 and No.6 of 4.16kV motors failed near rated voltage of 5.6kV and 4.2kV, respectively. Almost all of failures were located in a line-end coil at the exit from the core slot. The breakdown voltages and the types of defects showed strong relation to the stator insulation tests such as in the case of AC current, dissipation factor(tan${\delta}$) and partial discharge magnitude.

The Study on tree growth in XLPE using PD patterns (부분방전 패턴을 이용한 가교폴리에틸렌에서의 트리성장에 관한 연구)

  • Kang, Dae-Yong;Wu, Guangning;Shin, Chang-Myon;Park, Myoung-Seop;Cho, Kyu-Bock;HwangBo, Seung;Park, Dae-Hee
    • Proceedings of the KIEE Conference
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    • 1998.11c
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    • pp.941-943
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    • 1998
  • Exploitation of equipment with cross linked polyethylene (XLPE) insulation requires its condition monitoring and diagnostic. Traditionally diagnostics of insulation is carried out by means of partial discharge detection. Many researchers have developed a lot of methods to identify the defect by the PD form. However, such identification of a defect, for example, void, inclusion or treeing, does not say about its danger from a point of view of full insulation gap breakdown and insulation construction failure. The information about the form and size of formed upon high voltage treeing is necessary for prediction of the remained resource of XLPE insulation. For this purpose we carry out experimental research for determination of the dependencies between PD characteristics in XLPE upon time and three dimension PD patterns of corresponding treeing. The investigations were carried out by means of electrical measurement of PD current and simultaneous optical recording of treeing image. Test results show that the PD patterns can be applied for detecting tree growth well.

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A Study on the Condition Diagnosis for the Stator Coil of Traction Motor by Transient Surge (과도서지에 의한 견인전동기 고정자 코일의 상태진단 연구)

  • 박현준;장동욱;김길동;최종선;김정수
    • The Transactions of the Korean Institute of Power Electronics
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    • v.8 no.3
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    • pp.247-252
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    • 2003
  • Aging and failure of motor insulation depend on the stresses imposed on it. The insulation life time depends on the severity of the stresses. The electrical aging by transient surge is very important to traction motor in EMU(electric multiple unit). This paper presents the insulation characteristics of stator coil by transient surge from inverter. There are several nondestructive tests available for checking the condition of motor insulation, the probable extent of aging, and the rate of which aging is taking place. So the insulation characteristics of stator coil were each analyzed by measurement of leakage current, dielectric loss(tan $\delta$), capacitance, polarization index(PI) and partial discharge. The method of diagnosis is able to analyze the aging condition and predict the life of the traction motor in EMU.

Assessment of Insulation Aging in 6.6 kV Class High Voltage Motor Stator Windings (6.6 kV급 고압전동기 고정자 권선의 절연열화 평가)

  • Kim, Hee-Dong;Kim, Byong-Han
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.11
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    • pp.1067-1071
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    • 2006
  • Prior to destructive testing, diagnostic tests were performed in ten high voltage motors. Diagnostic tests included polarization infer, ac current, dissipation factor$(tan{\delta})$ and partial discharge magnitude. The rewind of motet slater insulation at rated voltage is assessed by the results of these tests. After completing the diagnostic tests, the stator windings of motors were subjected to gradually increasing ac voltage, until the insulation punctured. No. 8 motor failed near rated voltage of 19.0 kV. The breakdown voltage of No. 4 motet was 7.0 kV which is lower that expected for good quality coils in 6.6 kV class motors. The failure was located in a line-end coil at the exit from the core slot. These two motors began operation in 1994. While testing No. 7 motor, flashover occurred between the stator winding and the stator frame at 15 kV. The relationship between the diagnostic test and the drop in insulation breakdown voltage was analyzed.

Assessment of Insulation Deterioration in Stator Windings of High Voltage Motor (고압전동기 고정자 권선의 절연열화 평가)

  • Kim, Hee-Dong;Kong, Tae-Sik
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.5
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    • pp.711-716
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    • 2012
  • To assess the insulation deterioration of stator windings, diagnostic and AC breakdown tests were performed on the eleven high voltage (HV) motors rated at 6kV. After completing the diagnostic tests, the AC overvoltage test was performed by gradually increasing the voltage applied to the stator windings until electrical insulation failure occurred, to obtain the breakdown voltage. Stator winding of motors 1, 3, and 8 failed at above rated voltage at 14 kV, 13.8kV, and 16.4kV, respectively. The breakdown voltage of three motors was higher than expected for good quality windings in 6kV motors. Based on deterioration evaluation criteria, the stator winding insulation of eleven HV motors are confirmed to be in good condition. The turning point of the current, $P_{i2}$, in the AC current vs. voltage characteristics occurred between 5kV and 6kV, and the breakdown voltage was low between 13.8kV and 16.4kV. There was a strong correlation between the breakdown voltage and various electrical characteristics in diagnostic tests including Pi2.