Investigation on Oil-paper Degradation Subjected to Partial Discharge Using Chaos Theory

Gao, Jun,Wang, Youyuan,Liao, Ruijin,Wang, Ke,Yuan, Lei,Zhang, Yiyi The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.5

In this paper, oil-paper samples composed of transformer windings were used to investigate the insulation degradation process subjected to partial discharge (PD), with artificial defects inside to simulate the PD induced insulation degradation. To determine appropriate test voltages, the breakdown time obtained through a group of accelerated electrical degradation tests under high voltages was firstly fitted by two-parameter Weibull model to acquire the average breakdown time, which was then applied to establish the inverse power law life model to choose advisable test voltages. During the electrical degradation process, PD signals were synchronously detected by an ultra-high frequency (UHF) sensor from inception to breakdown. For PD analysis, the whole degradation process was divided into ten stages, and chaos theory was introduced to analyze the variation of three chaotic parameters with the development of electrical degradation, namely the largest Lyapunov exponent, correlation dimension and Komogorov entropy of PD amplitude time series. It is shown that deterministic chaos of PD is confirmed during the oil-paper degradation process, and the obtained results provide a new effective tool for the diagnosis of degradation of oil-paper insulation subjected to PD.

Investigation on Oil-paper Degradation Subjected to Partial Discharge Using Chaos Theory

Jun Gao,Youyuan Wang,Ruijin Liao,Ke Wang,Lei Yuan,Yiyi Zhang 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.5

In this paper, oil-paper samples composed of transformer windings were used to investigate the insulation degradation process subjected to partial discharge (PD), with artificial defects inside to simulate the PD induced insulation degradation. To determine appropriate test voltages, the breakdown time obtained through a group of accelerated electrical degradation tests under high voltages was firstly fitted by two-parameter Weibull model to acquire the average breakdown time, which was then applied to establish the inverse power law life model to choose advisable test voltages. During the electrical degradation process, PD signals were synchronously detected by an ultra-high frequency (UHF) sensor from inception to breakdown. For PD analysis, the whole degradation process was divided into ten stages, and chaos theory was introduced to analyze the variation of three chaotic parameters with the development of electrical degradation, namely the largest Lyapunov exponent, correlation dimension and Komogorov entropy of PD amplitude time series. It is shown that deterministic chaos of PD is confirmed during the oil-paper degradation process, and the obtained results provide a new effective tool for the diagnosis of degradation of oil-paper insulation subjected to PD.

UV-Vis 분광분석에 의한 전기변압기 내 절연지 열화도 측정

공호성(Hosung Kong),한흥구(Hung-Gu Han) 한국트라이볼로지학회 2019 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.35 No.3

Insulated oil degradation produces charged by-products, such as acids and hydro-peroxides, which tend to reduce the insulating properties of the oil. In this study, UV-vis spectroscopy measurement technology is developed and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate its ability to monitor the degradation of electrical insulating paper. The degradation characteristics of the insulating paper are appropriately represented through various types of measurement methods, such as the Tan (delta) method, CO₂ gas production measurement, the titration method, and IR spectroscopy. The results are demonstrated to be well comparable to a change in the fluorescence emission ratio (FER), which is defined as the shift in fluorescence intensity in the measured wavelength range, and also to the chromatic ratio, which is defined as a color shift to longer wavelength ranges. The results also show that, by using UV-vis spectroscopy, it is possible to detect the degradation of the insulating paper. This study suggests that UV-vis spectroscopy can be applied as an alternative to high-performance liquid chromatography, which is the internationally recognized measurement technology for cellulose paper degradation. The FER detector is also verified to be useful as an effective condition-monitoring device for power transformers.

IV 및 HIV 절연전선의 가속열화에 따른 절연피복의 성능변화에 관한 연구

최수길,김시국 한국화재소방학회 2019 한국화재소방학회논문지 Vol.33 No.2

The paper relates to a study on the changes in performance of insulation sheath resulting from accelerated degradationof IV and HIV insulated wire. To assume insulation degradation of IV and HIV insulated wire, accelerated life tests usingArrhenius equation were conducted among accelerated life test models, and experimental samples of 0 year, 10 years, 20years, 30 years, and 40 years in equivalent life were produced. Whereas the maximum tensile load were increased asaccelerated degradation of IV and HIV insulated wire progressed, elongation percentage, rupture time, and flexibility ofinsulated wires were found to be gradually reduced. According to the additional surface analysis results for the insulatedwires per equivalent life using a scanning electron microscope, mechanical properties of the insulator were observed to bereduced as insulation degradation resulting from aging progressed since phenomena such as formation of crystallinestructures and perforation, etc. occurred on the sample surface with progression of accelerated degradation. Consequently,institutional replacement of insulated wires and preparation of repair times considering performance degradation of theinsulator installed inside buildings are considered necessary in order to prevent in advance the risks of electrical fireresulting from degradation in insulation performance. 본 논문은 IV 및 HIV 절연전선의 가속열화에 따른 절연피복의 성능변화에 관한 연구이다. IV 및 HIV 절연전선의절연열화를 가정하기 위해 가속수명시험 모형 중 아레니우스 방정식을 이용한 가속수명시험을 진행하였고, 등가수명 0년, 10년, 20년, 30년, 40년 실험시료를 제작하였다. IV 및 HIV 절연전선의 가속열화가 진행됨에 따라 최대인장하중은 커지는 반면, 절연전선의 신장률, 파단시간, 유연성이 점차 감소되는 것으로 나타났다. 추가적인 주사전자현미경을 이용한 등가수명별 절연전선 표면 분석 결과 가속열화가 진행됨에 따라 시료 표면에 결정형 구조 및 천공 등의현상이 발생되어 노후화에 따른 절연열화가 진행 될수록 절연체의 기계적 특성이 감소되는 것으로 나타났다. 따라서절연성능 저하에 따른 전기화재 위험성을 사전에 예방하기 위해선 건축물 내에 설치되는 절연체의 성능저하를 고려한 제도적인 절연전선의 교체 및 보수시기의 마련이 필요할 것으로 생각된다.

Clarification of performance degradation of 20 Ah LIB pouch cell after use in electric bus

Cho, Yong-Nam,Hwang, Keebum,Bae, Joong Ho,Kim, Jaekwang,Lee, Ilbok,Kim, Nayoung,Ahn, Junghoon,Song, Jun-Ho,Yoon, Songhun Elsevier 2018 Journal of Electroanalytical Chemistry Vol.829 No.-

<P><B>Abstract</B></P> <P>Herein, performance degradation of pouch type of 20 A h lithium ion battery from electric bus is clarified after a classification using the resistance value from A to D grade. The obtained cells are carefully disassembled to produce cathode, anode, and separator. Scanning electron microscopy and energy dispersive spectroscopy analysis reveal that morphological change of electrode mostly occur in the anodes surface in D-grade cells, while cathodes of all the grades mostly remain similar. Although the change of crystalline structure of all electrodes is negligible, a growth of solid-electrolyte interphase film mostly happen in the D-grade anodes, which is confirmed by X-ray photoelectron spectroscopy analysis. Furthermore, the degradation of cycle and rate performance happen in the anode of D-grade cells, whereas the cathodes remain invariant irrespective of grade. Furthermore, the disassembled separators exhibit that the Gurley number of separators is commonly increased in the used cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The used 20 Ah lithium ion pouch cells from electric bus were classified using resistance. </LI> <LI> The LIB cells separated in 4 grade level were dissembled to obtain cathode, anode and separator. </LI> <LI> Surface film increase occurred in anode in D graded LIB cells. </LI> <LI> Resistance increase and capacity decrease were mostly attributed to anode degradation. </LI> <LI> Cathode and separator remained less-changed by real operation. </LI> </UL> </P>

Electric-Field Induced Degradation of Ionic Solids

전자규,류한일 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.1

Degradation of performance and life time of a functional material or device thereof is induced, to a great extent, by mass transfer in the material that is driven by various thermodynamic forces imposed intentionally or accidentally during its operation or service. The forces are any gradient of intensive thermodynamic variables, component chemical potentials, electrical potential, temperature, stresses, and the like. This paper reviews electric-field induced degradation phenomena in ionic solid compounds including insulation resistance degradation, crystal shift, microstructural alterations, compositional unmixing, and compound decomposition. Their inner workings are also discussed qualitatively.

Electric-Field Induced Degradation of Ionic Solids

Chun, Ja-Kyu,Yoo, Han-Ill The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.1

Degradation of performance and life time of a functional material or device thereof is induced, to a great extent, by mass transfer in the material that is driven by various thermodynamic forces imposed intentionally or accidentally during its operation or service. The forces are any gradient of intensive thermodynamic variables, component chemical potentials, electrical potential, temperature, stresses, and the like. This paper reviews electric-field induced degradation phenomena in ionic solid compounds including insulation resistance degradation, crystal shift, microstructural alterations, compositional unmixing, and compound decomposition. Their inner workings are also discussed qualitatively.

Electricity generation from iron EDTA-based liquid redox sulfur recovery process with enhanced stability of EDTA

Kim, K.,Kim, D.Y.,Lee, K.R.,Han, J.I. Pergamon ; Elsevier Science Ltd 2013 Energy conversion and management Vol.76 No.-

In this study, an innovative iron EDTA-based H<SUB>2</SUB>S capture technology was proposed. Just like currently available approaches, this system allows to capture H<SUB>2</SUB>S and convert it into element sulfur. It does so, however, with net energy production and without absorbent degradation. The system, consisting of an absorber and a fuel cell units, absorbs gaseous H<SUB>2</SUB>S and oxidize it to elemental sulfur in the absorber compartment, and in the fuel cell unit converts the reduced form of the absorbent [Fe(II)EDTA]<SUP>2-</SUP> back to [Fe(III)EDTA]<SUP>-</SUP>, generating electricity. When solution pH was raised from 7 to 10, more gaseous H<SUB>2</SUB>S was absorbed into [Fe(III)EDTA]<SUP>-</SUP>, resulting in increased production [Fe(II)EDTA]<SUP>2-</SUP>. This reduced form of the absorbent, which should be subsequently regenerated for continuous operation, serves as a fuel in a Fe(II)-based fuel cell. Fuel cell performance was also found to be strongly affected by solution pH, and the highest maximum power density of 0.832mWcm<SUP>-2</SUP> was achieved at pH 9 and 60<SUP>o</SUP>C. At this condition, more than 80% of [Fe(III)EDTA]<SUP>-</SUP> was recovered from [Fe(II)EDTA]<SUP>2-</SUP> in 2h without any noticeable degradation of EDTA, amounted to the oxidation rate of 147gFeh<SUP>-1</SUP>m<SUP>-2</SUP> anode surface area. This study provides demonstration of many desirable aspects for field implementation, such as electricity generation, sulfur recovery and long-term stability of the absorbent.

가속열화에 따른 IV절연전선 피복의 과전류 특성에 관한 연구

김시국,최수길 한국화재소방학회 2018 한국화재소방학회논문지 Vol.32 No.2

This paper reports the results of a study on the over-current characteristics of IV insulated wire sheath according toaccelerated degradation. In order to examine the degradation of a IV insulated wire sheath through insulation, accelerationdegradation experiments were performed using the Arrhenius equation of acceleration life test models; test samples withequivalent lives of 0, 10, 20, 30 and 40 years were prepared. Then allowed currents with over-current of 100%~500% wereintroduced to measure the times of first generation of smokes and carbonization in the wire sheath, and it was found that thetimes of first generation of smokes and carbonization in the wire sheath decreased as the equivalent life increased. In moredetail, when 270% over-current is applied, the electrical fire risk of equivalent life of 40 years increased by approximately3.2 times based on equivalent life of 0 years. Also, when the over-current was 255% and 260%, carbonization occurred onlyin the equivalent life of 40 years, and the fire risk according to the accelerated degradation was increased dramatically. Inaddition, FT-IR and SEM analyzes were used to confirm the characteristics and surface changes of IV insulated wire sheathaccording to the equivalent life. 본 논문은 가속열화에 따른 IV절연전선 피복의 과전류 특성에 관한 연구이다. IV절연전선 피복의 절연열화를 위해 가속수명시험 모형 중 아레니우스 방정식을 이용한 가속열화실험을 진행하여 등가수명 0년, 10년, 20년, 30년, 40년 실험시료를 제작하였다. 그 후 실험시료 대상으로 허용전류 100%~500% 과전류를 인가하여 전선피복에서 최초연기 및 탄화 발생시간을 측정하였고, 등가수명이 증가함에 따라 최초 연기 및 탄화 발생시간이 감소하는 것으로나타났다. 세부적으로 과전류 270%에서 등가수명 0년을 기준으로 등가수명 40년의 전기화재 위험성이 3.2배 증가하였다. 또한, 과전류 255% 및 260% 인가 시 등가수명 40년에서만 탄화가 발생하여 가속열화에 따른 화재위험성이 비약적으로 증가하는 것으로 나타났다. 추가적으로 FT-IR과 SEM을 이용하여 IV절연전선 피복의 등가수명에 따른 특성 및 표면 변화의 차이를 확인하였다.

Analysis on the electrical degradation characteristics of 2G HTS wires with respect to the electrical breakdown voltages

Kang, Jong O,Lee, Onyou,Mo, Young Kyu,Kim, Junil,Bang, Seungmin,Lee, Hongseok,Lee, Jae-Hun,Jang, Cheolyeong,Kang, Hyoungku The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.3

Recently, the electrical insulation design for electrical apparatuses is important to cope with the tendency of high voltage. The degradation characteristics of a superconducting coil due to an electrical breakdown should be considered to design a high voltage superconducting coil. In this paper, the degradation characteristics of 2G high temperature superconducting (HTS) wires are studied with respect to electrical breakdown tests. To analyze the dependency of the degradation characteristics of 2G HTS wires, the electrical breakdown tests are performed with AC(alternating current) and DC(direct current) voltage. All tests are performed by applying various magnitudes of AC and DC breakdown voltages. To verify the degradation characteristics of 2G HTS wires, the tests are performed with various 2G HTS wires with respect to stabilizer materials. The degradation characteristics of 2G HTS wires, such as Ic(critical current) and index number are measured by performing electrical breakdown tests. It is found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it is concluded that the degradation characteristics of 2G HTS wires are affected by the stabilizer material and applied voltages. The cross-sectional view of 2G HTS wires is observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS wires are concerned with hardness and electrical conductivity of stabilizer layers.