Guard-Gap Correction for Guarded-Electrode Measurements and Exact Equations for the Two-Fluid Method of Measuring Permittivity and Loss

Meltzer, RL; Fiorini, YR; Horstman, RT; Moore, IC; Batik, AL; Endicott, H. S.

doi:10.1520/jte10200j

Cited by 10 publications

(3 citation statements)

References 6 publications

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“…The effective radius of the measuring electrode has been well studied and analytical expressions have been developed [3][4][5][6][7][8][9]. Because the edge radius r has not been considered in the guarded electrode system, it is, therefore, necessary to reverify the validity of the correction equations proposed in the current international standards.…”

Section: Evaluation Of Correction Equations From the Current Internat...mentioning

confidence: 99%

“…This effective area of the measuring electrode is actually larger than its geometrical surface due to the edge fringing effect. The effective radius of the measuring electrode has been well investigated and several correction expressions have been obtained [3][4][5][6][7][8][9]. Thomson used conformal transformation to obtain the field distribution in a guarded electrode system [3].…”

Section: Introductionmentioning

confidence: 99%

“…Thomson used conformal transformation to obtain the field distribution in a guarded electrode system [3]. Lauritzen and Endicott have derived correction expressions for both thin and thick electrodes based on Thomson's work [4,5]. Amey calculated an effective radius under the condition that the permittivity of the sample is much higher than that of air [6].…”

Section: Introductionmentioning

confidence: 99%

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Study of a guarded electrode system in the dc conductivity measurement of insulating liquid

Zhou

Hao

Wilson

et al. 2014

Meas. Sci. Technol.

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The design and choice of an electrode system is important in dc conductivity measurement of insulating liquid. In this paper, the electric field distribution of an electrode system which consists of two parallel circular metallic electrodes and a guard electrode has been studied using Comsol Multiphysics software. A new parameter, which is not yet involved in current standards, the edge radius, has been mentioned in the literature formerly and is currently discussed in a CIGRE working group. In this paper, the influence of this parameter has been investigated by means of field calculation. As seen from the simulating result, there are regions in the vicinity of the edges of the guard and measuring electrode that are under high electric field. If the edges of these two electrodes are sharp, the maximum electric field in the test cell will be much higher than the average field between the measuring electrode and the high voltage electrode. An empirical equation has been proposed to calculate this maximum field. The classic correction expression for an effective radius has been re-evaluated with the edge radius being taken into account. Experimental work has been performed to confirm this conclusion. Three kinds of mineral oils with different ageing times have been tested under the dc field using a guarded electrode system and the electric strengths of these oils have been estimated. A recommendation has been made to current standards in insulating liquid measurement.

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Section: Evaluation Of Correction Equations From the Current Internat...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of a guarded electrode system in the dc conductivity measurement of insulating liquid

Zhou

Hao

Wilson

et al. 2014

Meas. Sci. Technol.

View full text Add to dashboard Cite

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Measurement of dielectric constant and conductivity of samples using guarded electrodes

Darayan¹,

Shattuck²,

Shen³

et al. 1996

Radio Science

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A laboratory apparatus is designed to measure the complex permittivity of both liquid and solid samples in the frequency range from 2 to 13 MHz. This device uses a guarded-electrode sample holder to significantly reduce fringe effects. A synthetic focusing method is utilized to ensure that the potentials at both the main and the guard electrodes are equal. Extensive measurements on NaC1 solutions of different salinities are made to study the accuracy of the guarded-electrode method. The measured complex permittivities are in good agreement with those reported in the literature. The deviation is less than 3% for the conductivity measurement and depends on the salinity of the solution for the dielectric constant measurement.Various measurements conducted on Berea sandstones and glass beads saturated with saline water showed the accuracy and feasibility of the experimental set up. This measurement method might be used to obtain accurate values for the conversion of measured data from the measurement while drilling (MWD) resistivity tool. 1417 1418 DARAYAN ET AL.: GUARDED ELECTRODE MEASUREMENTS tler• el Guard electrode ectrode,• Field lines

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Model‐based accuracy enhancements for guarded conductivity measurements: determination of effective electrode areas utilising numerical field simulation

Freye

Jenau

2018

High Voltage

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Methods utilising current measurements for conductivity and permittivity determination require precise knowledge of the effective electrode area in order to obtain accurate results. Owing to field distortions (e.g. caused by fringing) in guarded electrode setups, the effective electrode area differs significantly from the geometrical calculated. Focusing on guarded electrode setups for conductivity determination, a generic method based on numerical field simulation is presented allowing a convenient determination of the relevant effective electrode area. For this purpose, a brief overview of yet existing normative guidelines and related research work is provided. State-of-the-art conductivity measurement setups are presented in order to identify parameters which affect the field distribution within the measurement arrangements. The description of the implemented method and its realisation in COMSOL multiphysics is followed by its validation using analytical fringing calculations. Furthermore, presented method is used for the evaluation of fringing effects and additional field distortion caused by design aspects of the measurement cell itself and potential imbalances related to the measurement setup. Moreover, dependencies on conductivity of the surrounding environment are considered. Achieved model-based accuracy enhancements are calculated and are leading to a gain in precision for conductivity determination of up to 25% compared to yet existing approaches.

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Guard-Gap Correction for Guarded-Electrode Measurements and Exact Equations for the Two-Fluid Method of Measuring Permittivity and Loss

Cited by 10 publications

References 6 publications

Study of a guarded electrode system in the dc conductivity measurement of insulating liquid

Study of a guarded electrode system in the dc conductivity measurement of insulating liquid

Measurement of dielectric constant and conductivity of samples using guarded electrodes

Model‐based accuracy enhancements for guarded conductivity measurements: determination of effective electrode areas utilising numerical field simulation

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