• Title/Summary/Keyword: negative DC potential

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An Analysis of Influence Between the Power Feeding Line Insulation and Negative Rail Potential for the DC Ground Fault Protection in the Rubber Wheel System (고무차륜시스템에서의 지락보호를 위한 급전선로 절연과 부극전위와의 영향 분석)

  • Jung, Hosung;Shin, Seongkuen;Kim, Hyungchul;Park, Young;Cho, Sanghoon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.4
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    • pp.577-583
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    • 2013
  • We have analyzed influence of potential rise in negative bus, which caused by decrease of power feeding line insulation, upon protecting method of DC ground protection device which detecting potential rise between negative bus and ground in order to detect ground fault in the rubber wheel system. For this purpose, we proposed negative potential equation between negative bus and ground and calculated negative potential according to system condition changes by estimating power feeding line insulation changes in steel wheel system and rubber wheel system, and equalizing DC power feeding system when ground fault occurred. Also, in order to estimate negative potential of real system, we modeled the rubber wheel system, and simulated normal status, grounding fault occurrence and power feeding line insulation changes. In normal status, negative potential did not rise significantly regardless of vehicle operation. When ground fault occurred, negative potential rose up over 300V regardless of fault resistance. However, we also observed that negative potential rose when power feeding line insulation dropped down under $1M{\Omega}$. In conclusion, our result shows that in case of rubber wheel system unlike steel wheel system, relay will be prevented maloperation and insulation status observation can be ensured when ground over voltage relay will be set 200V ~ 300V.

A Study on the Dry Cleaning of Aluminium Surfaces by Low Temperature Plasma Process (저온 플라스마 공정을 이용한 알루미늄 표면의 건식 세정에 관한 연구)

  • Lim, Gyeong-Taek;Kim, Kyung Hwan;Kim, Kyung Seok;Li, Hui Jie;Song, Sun Jung;Shon, Hokyong;Cho, Dong Lyun
    • Applied Chemistry for Engineering
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    • v.19 no.6
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    • pp.640-644
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    • 2008
  • Lubricating oil on aluminium surfaces was cleaned by a low temperature plasma process. Oxygen plasma mixed with argon was used, and process parameters were the mixing ratio of argon in oxygen, discharge power, and negative DC potential. The aluminium surfaces were analyzed with FTIR and EDX after the cleaning. It was found that almost all of the oil was eliminated in 20 min. if the oil was pure. Elimination efficiency was highly dependent on operational conditions of the process. The highest efficiency was obtained when treated at 300 W with oxygen plasma mixed with 30% argon applying negative potential more than -500 V on the aluminium surfaces. However, efficiency higher that 60% cannot be obtained at any condition if the oil contained inorganic materials.

An Analysis on Rise of Rail Potential And A Study on Control Method for It in DC Feeding System (직류급전계통에서의 레일전위 상승 분석 및 억제 방안 연구)

  • Min, Myung-Hwan;Jung, Ho-Sung;Park, Young;Kim, Hyeng-Chul;Shin, Myong-Chul
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.3
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    • pp.680-685
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    • 2011
  • Nowadays, in metropolitan railroad, DC feeding system is being generally applied. In order to reduce damages of electro-chemical corrosion caused by stray current and leakage current, in DC feeding system, rail is used as negative-polarity return conductor for traction load current. However, it has problem of rail potential increase and there are no adequate measures to prevent it in domestic. In this paper, we presented fundamental theory and related standards about rail potential increase. And then, we analyzed field testing data and simulated a variety of operations by using PSCAD/EMTDC as an analysis program of power system. In addition, voltage control device is suggested to prevent accidents caused by rail potential increase.

A Control Technique for the Rail Potential Limit Device in DC Feeding System (직류급전계통에서 레일전위상승제한장치의 동작제어기법)

  • Min, Myung-Hwan;Jung, Ho-Sung;Park, Young;Chang, Sang-Hoon;Shin, Myong-Chul
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.3
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    • pp.485-490
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    • 2012
  • Nowadays, in metropolitan railroad, DC feeding system is being generally applied. In order to reduce damage of electro-chemical corrosion caused by stray current and leakage current, in DC feeding system, rail is used as negative-polarity return conductor for traction load current. However, it has problem of rail potential increase and there are no adequate measures to prevent it in domestic. The rise of rail potential leads to damage for human and equipments. To solve the problems, this paper presents fundamental theory and related standards about rail potential increase. And then, we analyzed field testing data and simulated a variety of operations by using PSCAD/EMTDC as an analysis program of power system. In addition, this paper suggests rail potential limit device and addresses how to the device. To verify the effect, simulation of DC feeding system before and after the application of the device is carried out in various cases.

The Effect of Substrate DC Bias on the Low -Temperature Si homoepitaxy in a Ultrahigh Vacuum Electron Cyclotron Resonance Chemical Vapor Deposition (초고진공 전자 사이클로트론 화학 기상 증착 장치에 의한 저온 실리콘 에피 성장에 기판 DC 바이어스가 미치는 영향)

  • 태흥식;황석희;박상준;윤의준;황기웅;송세안
    • Journal of the Korean Vacuum Society
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    • v.2 no.4
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    • pp.501-506
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    • 1993
  • The spatial potential distribution of electron cyclotron resonance plasma is measured as a function of tehsubstrate DC bias by Langmuir probe method. It is observed that the substrate DC bias changes the slope of the plasma potential near the subsrate, resulting in changes in flux and energy of the impinging ions across plasma $_strate boundary along themagnetric field. The effect of the substrate DC bias on the low-temperature silicon homoepitaxy (below $560^{\circ}C$) is examine dby in situ reflection high energy electron diffraction (RHEED), cross-section transmission electron microscopy (XTEM),plan-view TEM and high resolution transmision electron microscopy(HRTEM). While the polycrystalline silicon layers are grow withnegative substrate biases, the single crystaline silicon layers are grown with negative substrate biases, the singel crystalline silicon layers are grown with positive substrate biases. As the substrate bias changes form negative to positive values, the growth rate decreases. It is concluded that the control of the ion energy during plasma deposition is very important in silicon epitaxy at low temperatures below $560^{\circ}C$ by UHV-ECRCVD.VD.

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The Effect of External DC Electric Field on the Atmospheric Corrosion Behaviour of Zinc under a Thin Electrolyte Layer

  • Liang, Qinqin;YanYang, YanYang;Zhang, Junxi;Yuan, Xujie;Chen, Qimeng
    • Corrosion Science and Technology
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    • v.17 no.2
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    • pp.54-59
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    • 2018
  • The effect of external DC electric field on atmospheric corrosion behavior of zinc under a thin electrolyte layer (TEL) was investigated by measuring open circuit potential (OCP), cathodic polarization curve, and electrochemical impedance spectroscopy (EIS). Results of OCP vs. time curves indicated that the application of external DC electric field resulted in a negative shift of OCP of zinc. Results of cathodic polarization curves measurement and EIS measurement showed that the reduction current of oxygen increased while charge transfer resistance ($R_{ct}$) decreased under the external DC electric field. Variation of OCP negative shift, reduction current of oxygen, and $R_{ct}$ increase with increasing of external DC electric field strength as well as the effect of external DC electric field on double-layer structure in the electrode/electrolyte interface and ions distribution in thin electrolyte layer were analyzed. All results showed that the external DC electric field could accelerate the corrosion of zinc under a thin electrolyte layer.

Modeling for the Analysis of Rail Potential in the DC Railway Power System (직류전기철도 급전시스템에서 레일전위 해석을 위한 모델링)

  • Cho, Woong-Ki;Choi, Kyu-Hyoung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.6
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    • pp.138-146
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    • 2010
  • DC railway power supply system generally uses the running rails as negative-polarity return conductor for traction load current, and the induced rail potential and stay current cause serious problems to any electrified matter in the underground and also safety problems to human body. This paper presents a new algorithm for the analysis of the rail potential and the stray current in DC railway power system operated under independent/parallel power feeding mode. The effect of load current fluctuation during train operation is also calculated by using TPS(Train Performance Simulation) program to analysis the variation of the railway potential and stray current along railway track. Simulation program is developed based on the proposed algorithm and case studies are provided.

An Algorithm to Analyze Rail Potential Rise in DC Traction Power Supply System (레일전위상승 분석을 위한 컴퓨터 알고리즘)

  • Chung, Sang-Gi;Kim, Hyung-Chul;Jung, Ho-Sung;Kwon, Sam-Young
    • Journal of the Korean Society for Railway
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    • v.12 no.5
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    • pp.687-693
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    • 2009
  • An algorithm and a computer software are developed for the analysis of rail potential rise. The algorithm is intended to be integrated with the traction power system simulation program. In the algorithm, rail potentials are obtained by two step process. First the injection currents to the negative rail are obtained from load-flow study. In the next step, a network consisting of negative rail and the injection currents are constructed. Leakage resistance to ground are added to the network. And the network is analyzed for rail potentials. A software is developed to verify the validity of the algorithm. The result of the software is compared with the Simulink/SymPower circuit analysis result. The differences between the two results are with the acceptable range. The advantage of this algorithm is that it can be integrated with the existing traction power supply simulation program easily, which usually ignores negative rail's leakage resistance.

Trichel Pulse in Negative DC Corona discharge and Its Electromagnetic Radiations

  • Zhang, Yu;Liu, Li-Juan;Miao, Jin-Song;Peng, Zu-Lin;Ouyang, Ji-Ting
    • Journal of Electrical Engineering and Technology
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    • v.10 no.3
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    • pp.1174-1180
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    • 2015
  • We investigate in this paper the radiated electromagnetic waves together with the discharge characteristics of Trichel pulse of negative DC corona discharge in air in pin-to-plate and wire-to-plate configurations. The feature of the current pulse and the frequency spectrum of the electromagnetic radiations were measured under various pressures and gas gaps. The results show that the repetition frequency and the amplitude of Trichel pulse current depend on the discharge conditions, but the rising time of the pulse relates only to the radius of needle or wire and keeps constant even if the other conditions (including the discharge current, the gas gap and the gas pressure) change. There exists the characterized spectrum of electromagnetic waves from negative corona discharge in Trichel pulse regime. These characterized radiations do not change their frequency at a given cathode geometry even if the averaged current, the gas gap or the air pressure changes, but the amplitude of radiations changes accordingly. The characterized electromagnetic radiations from Trichel pulse corona relate to the formation or the rising edge of current pulse. It confirms that the characterized radiations from Trichel pulse supply information of discharge system and provide a potential method for detecting charged targets.

A Study on the Relationships between Substrate Bias Potential and Ion Energy Distributions (이온 플레이팅에서 기판 BIAS 전위와 이온 에너지 분포와의 상관관계 연구)

  • Sung, Y.M.;Shin, J.H.;Son, J.B.;Cho, J.S.;Park, C.H.
    • Proceedings of the KIEE Conference
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    • 1995.11a
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    • pp.472-474
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    • 1995
  • A Sputter ion Plating(SIP) system with a r.f. coil electrode and the Facing Target Sputter(FTS) source was designed for high-quality thin film formation. The rf discharge was combined with DC facing target sputtering in order to enhance ionization degree of a sputtered atoms. The energy of ions incident on the substrate depended on the health potential of DC biased substrate. The mean impact ion energy increased with negative bias voltage and rf power. The adhesive force of the TiN film formed was in the range of 30$\sim$50N, and markedly influenced by substrate bias voltage.

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