• Title, Summary, Keyword: Resistance measurement

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Uncertainty evaluation in electrochemical noise resistance measurement (전기화학적 노이즈 저항 측정에서의 불확도 평가)

  • Kim, Jong Jip;Kang, Su Yeon
    • Corrosion Science and Technology
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    • v.12 no.5
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    • pp.220-226
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    • 2013
  • The uncertainty in statistical noise resistance measurement was evaluated for a type 316 stainless steel in NaCl solutions at room temperature. Sensitivity coefficients were determined for measurands or variables such as NaCl concentration, pH, solution temperature, surface roughness, inert gas flow rate and bias potential amplitude. The coefficients were larger for the variables such as NaCl concentration, pH, inert gas flow rate and solution temperature, and they were the major factors increasing the combined standard uncertainty of noise resistance. However, the contribution to the uncertainty in noise resistance measurement from the above variables was remarkably low compared to that from repeated measurements of noise resistance, and thus, it is difficult to lower the uncertainty in noise resistance measurement significantly by lowering the uncertainties related with NaCl concentration, pH, inert gas flow rate and solution temperature. In addition, the uncertainty in noise resistance measurement was high amounting to 17.3 % of the mean, indicating that the reliability in measurement of noise resistance is low.

Estimation of Uncertainty of Measurement and Contribution Factor of Measurement Factor in Calibration Test of Standard Test Method for Thermal Resistance for Windows and Doors (창호 단열성 시험의 교정시험 측정불확도 추정 및 계측인자 기여율 분석)

  • Park, Jung-Hwan;Cho, Soo;Hong, Won-Hwa
    • 한국건축친환경설비학회 논문집
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    • v.11 no.2
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    • pp.121-130
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    • 2017
  • Thermal resistance test of windows and doors is required calibration test, which 'calibration test of the surface air-film resistance by CRM(Certified reference material)' and 'Correction calorimetric test of guarded hot box and edge of surrounding panel by CRM'. These two calibration test involve many metrics and complex procedures, which can lead to reliability problems in test results. In addition, it is necessary to understand the calibration test and to find a way to lower the uncertainty of measurement by analyzing contribution rate of the measurement factors. This paper is a follow up study of "Estimation on Uncertainty of Measurement on Thermal Resistance Test for Windows And Doors" and perform the uncertainty of measurement estimation of calibration test excluded from follow up study. As a result, the uncertainty of measurement estimation procedure for the thermal resistance test for windows and doors is proposed. In addition, according to analysis of the contribution rate of the measurement factor, the contribution rate of surface air-film resistance of warm side($R_i$) was the highest at 49.643%.

Development of AC Resistance Measurement System (교류저항 측정시스템 개발)

  • Kim, Han-Jun;Yu, Kwang-Min;Kang, Jeon-Hong;Han, Sang-Ok
    • Proceedings of the KIEE Conference
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    • pp.683-684
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    • 2008
  • The resistance is frequency dependent by the Seeback effect, loading effect, Eddy current loss, uniformly distributed inductance of the resistance element and uniformly distributed self-capacitance of the resistance element and capacitance between resistance element and it's box. A precise ac resistance measurement system has been developed for using as maintaining and dissemination of national ac resistance standards. The developed resistance measurement system can be used as a instrument of national ac resistance standards at frequency less than 10 kHz and it's measurement accuracy was 0.23(${\mu}{\Omega}/{\Omega}$)+4.2 ${\mu}{\Omega}$ at 1592 Hz and 20 V.

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Study on Development of the Isolation Resistance Measurement System for Hydrogen Fuel Cell Vehicle (수소연료전지자동차용 절연저항 측정시스템 개발에 관한 연구)

  • Lee, Ki-Yeon;Kim, Dong-Ook;Moon, Hyun-Wook;Kim, Hyang-Kon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.5
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    • pp.1068-1072
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    • 2011
  • Hydrogen Fuel Cell Vehicle(HFCV) is system that uses electrical energy of fuel cell stack to main power source, which is different system with other vehicles that use high-voltage, large-current. Isolation performance of this system which is connected with electrical fire and electrical shock is important point. Isolation resistance of electric installation is divided according to working voltage, it follows criterion more than $100{\Omega}$/VDC (or $500{\Omega}$/VAC) about system operation voltage in a hydrogen fuel cell vehicle. Although measurement of isolation resistance in a hydrogen fuel cell vehicle is two methods, it uses mainly measurement by megger. However, the present isolation resistance measurement system that is optimized to use in electrical facilities is unsuitable for isolation performance estimation of a hydrogen fuel cell vehicle because of limit of maximum short current and difference of measurement resolution. Therefore, this research developed the isolation resistance measurement system so that may be suitable in isolation performance estimation of a hydrogen fuel cell vehicle, verified isolation performance about known resistance by performance verification of laboratory level about developed system, and executed performance verification through comparing results of developed system by performance verification of vehicle level with ones of existing megger. Developed system is judged to aid estimation and upgrade of isolation performance in a hydrogen fuel cell vehicle hereafter.

A Study on the Measurement of Footing Resistance of Transmission Towers with Overhead Grounding wires (가공지선이 연결된 송전철탑의 탑각저항 측정에 관한 연구)

  • Lee, Won-Kyo;Choi, Jong-Kee;Lee, Young-Woo;Choi, In-Hyuk;Kim, Kyung-Chul
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.23 no.1
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    • pp.61-64
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    • 2010
  • Footing Resistance of a 154 kV transmission towers in korea is commonly required to be less than 15 ohm to avoid lightning back-flashover accident. The periodic measurement of Footing Resistance is important to verify that the grounding performance of the towers has been maintained good. Towers are electrically connected in parallel with overhead grounding wire, therefore footing resistance of each tower will be measured after disconnecting the overhead ground wires from the towers. however, In this paper, three direct measurement methods of footing resistance are presented. There are very useful methods without disconnecting overhead ground wires from the tower under measurement. They are compared in KEPCO 154 kV transmission towers. The experimental results describe performances of them.

A Study on the Improvement of Electrode Installation for Measurement of Ground Resistance through Investigation on the Spot in Buildings (현장조사를 통한 건축물 접지저항 측정용 전극 설치의 개선에 관한 연구)

  • Gil, Hyoung-Jun;Kim, Dong-Woo;Kil, Gyung-Suk
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.5
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    • pp.92-97
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    • 2011
  • This paper deals with the improvement of electrode installation for measurement of ground resistance through investigation on the spot in buildings. The investigation was carried out for an earthing terminal board for measurement of ground resistance, installation of auxiliary electrode, etc. The criteria value is set up by measuring method of ground resistance in international standard. In case of inadequate installation of auxiliary electrode, a relative error is analyzed and adequate installation method of auxiliary electrode is proposed. As a consequence, it is necessary to write direction of ground and equipment, and separate auxiliary electrode for measurement of ground resistance in order to minimize measuring error.

Monitoring Failure Behaviour of Pultruded CFRP Composites by Electrical Resistance Measurement

  • Mao, Yaqin;Yu, Yunhua;Wu, Dezhen;Yang, Xiaoping
    • Carbon letters
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    • v.5 no.1
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    • pp.18-22
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    • 2004
  • The failure behaviours of unidirectional pultruded carbon fiber reinforced polymer (CFRP) composites were monitored by the electrical resistance measurement during tensile loading, three-point-bending, interlaminar shear loading. The tensile failure behaviour of carbon fiber tows was also investigated by the electrical resistance measurement. Infrared thermography non-destructive evaluation was performed in real time during tensile test of CFRP composites to validate the change of microdamage in the materials. Experiment results demonstrated that the CFRP composites and carbon fiber tows were damaged by different damage mechinsms during tensile loading, for the CFRP composites, mainly being in the forms of matrix damage and the debonding between matrix and fibers, while for the carbon fiber tows, mainly being in the forms of fiber fracture. The correlation between the infrared thermographs and the change in the electrical resistance could be regarded as an evidence of the damage mechanisms of the CFRP composites. During three-point-bending loading, the main damage forms were the simultaneity fracture of matrix and fibers firstly, then matrix cracking and the debonding between matrix and fiber were carried out. This results can be shown in Fig. 9(a) and (b). During interlaminar shear loading, the change in the electrical resistance was related to the damage degree of interlaminar structure. Electrical resistance measurement was more sensitive to the damage behaviour of the CFRP composites than the stress/time curve.

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Precise Measurement of High Current Shunt Resistance (대전류 분류기 저항의 정밀측정)

  • Kim K.-T.;Han K.-S.;Kwon S.-W.;Kim M.-S.;Jeong J.Y.;Kim I.S.
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.54 no.9
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    • pp.403-406
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    • 2005
  • Precise measurement of extremely low resistance shunt is important for characterization and calibration of high current instruments. We tested resistance measurement method for extremely high current shunt (up to 140 kA), where resistance is determined by precise measurement of voltage drop at 10 A test current in the frequency range of 40 Hz to 10 kHz. For the extremely low ac voltage to be precisely measured, a verification of the measurement method was also carried, where the inherent noise is systematically evaluated. The measurement uncertainty was estimated to be $1\;\%\;at\;95\;\%$ confidence level (k=2) for about 50 $\mu\Omega$.

A New Measurement Method of the Ground Resistance Using a Low-pass Filter in Energized Substations (지역필터를 이용한 수변전실 접지저항의 새로운 측정방법)

  • Lee, Bok-Hui;Eom, Ju-Hong;Lee, Seung-Chil;Kim, Seong-Won;An, Chang-Hwan
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.50 no.8
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    • pp.387-393
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    • 2001
  • This paper describes an advanced measuring method and precise evaluation of the ground resistance for the grounding system of energized substations and power equipments. A grounding system of substations consists of all interconnected grounding connections of grounded conductors, neutral ground wires, underground conductors of distribution lines, cable shields, grounding terminals of equipments, and etc. It is very difficult to measure the accurate ground resistance of the grounding terminals of equipments, and etc. It is very difficult to measure the accurate ground resistance of the grounding system of high voltage energized substations because of harmonic components caused by switched power supplies or overloads. The conventional fall-of-potential method may be subject to big error if stray ground currents and potentials are present. In this work, to improve the precision in measurements of the ground resistance by eliminating the effects of harmonic components and stray currents and potentials, the investigations of the ground resistance measurement by using a low pass filter in a model energized grounding system were conducted. The accuracy of ground resistance mesurements was evaluated as a function of the ratio of the test signal to noise (S/N). The errors due to the proposed ground resistance measurement method were decreased with increasing S/N and were less than 5[%] as S/N is 10. The proposed ground resistance measurement method appears to be considerably more accurate than the conventional fall-of -potential method. It is allows cancellation of the parasitic resistance of energized grounding systems, to employ the measurement method that allows cancellation of the parasitic effects due to other circulating ground currents and ground potential rises in practical situations.

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The High Resistance Measurement up to 100 PΩ using a Low Resistance, a Low Voltage Source and a Commercial Digital Multimeter

  • Yu, Kwang Min;Lee, Sang Hwa;Kang, Jeon Hong;Kim, Wan-Seop
    • Journal of Electrical Engineering and Technology
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    • v.13 no.3
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    • pp.1392-1397
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    • 2018
  • The potentiometric measurement result for a high resistance up to $100P{\Omega}$ using a low resistance, a low voltage source and a commercial digital multimeter(DMM) is presented. With the method, a resistance can be easily, fast and economically measured. Using the method, resistance ranges over the $10G{\Omega}$ range which is difficult to measure using a commercial DMM and resistance ranges between $100T{\Omega}$ and $100P{\Omega}$ which cannot measure using an insulation tester were measured within accuracy of a few percent. It is expected that it can be useful to determine the temperature and voltage effect of a high resistance and an insulation material because it uses a reference resistance with a low resistance, very low temperature and voltage effect. Besides, it is expected that it can be useful to calibrate a dc high voltage divider with a large resistance ratio and a very low resistance because arbitrary resistance ratio measurements are possible with it.