Moisture dynamic measurements of transformer board using a three-wavelength dielectrometry sensor

Du, Yiqun; Zahn, M.; Mamishev, A.V.; Schlicker, Darrell

doi:10.1109/elinsl.1996.549281

Cited by 11 publications

(6 citation statements)

References 6 publications

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“…The paper-oil system was initially dried under vacuum and then the dry oil was removed and moist oil was introduced to the system. A three-wavelength interdigital sensor was used to monitor the moisture diffusion process [35,36]. The final moisture content in the pressboard and oil could be calculated using mass balance either from measurement or calculation using the oil-paper equilibrium moisture curves.…”

Section: Case Studymentioning

confidence: 99%

Moisture equilibrium in transformer paper-oil systems

Zahn²,

Lesieutre³

et al. 1999

IEEE Electr. Insul. Mag.

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324

135

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Key Words: Transformer paper, transformer oil, moisture equilibrium, vapor pressure, relative humidity he presence of moisture in a transformer deteriorates transformer insulation by decreasing both the electrical and mechanical strength. In general, the mechanical life of the insulation is reduced by half for each doubling in water content [l]; the rate of thermal deterioration of the paper is proportional to its water content [2]. Electrical discharges can occur in a high voltage region due to a disturbance of the moisture equilibrium causing a low partial discharge inception voltage and higher partial discharge intensity [ 3 ] . The migration of a small amount of moisture has been associated with flow electrification at paper/oil interfaces and is presumed to be due to charge accumulation on highly insulating interfacial dry zones [4,5]. Water in mineral oil transformers also brings the risk of bubble formation when desorption of water from the cellulose increases the local concentration of gases in the oil [6]. The importance of moisture presence in paper and oil systems has been recognized since the 1920s.It is useful to know the moisture partitioning curves between oil and paper under equilibrium conditions. When the transformer is in equilibrium operation, this provides a quick way of examining the moisture content in paper to predict future failure by measuring the moisture in oil. Over the years, many scientists have reported such a set of curves, but there has not been a comprehensive review and comparison for different curve sets. The research spans several decades and is an important resource for electric utilities and insulation and testing equipment manufacturers. This paper gives an overview of the classic moisture equilibrium curves and their history and provides useful information on the relationships among them and their validity.

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Section: Case Studymentioning

confidence: 99%

Moisture equilibrium in transformer paper-oil systems

Zahn²,

Lesieutre³

et al. 1999

IEEE Electr. Insul. Mag.

Self Cite

324

135

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“…Time-dependent dielectric response When a dielectric material is subjected to an electrical stress, the vectors called dielectric displacement D, which gives total charge density induced at the electrodes, and applied electric field E can be interrelated [10][11][12][13],…”

Section: Dielectric Response Of Insulationmentioning

confidence: 99%

The assessment of oil-paper insulation condition based on frequency response method

et al. 2010

2010 Annual Report Conference on Electrical Insulation and Dielectic Phenomena

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For analysis of the status of oil-paper insulation, the dielectric response method was used to model oil-paper insulation system. Then the dielectric spectroscopy of oil-paper insulation system was tested. And the influence of oil gap on the test results of oil-paper insulation response was discussed. The results showed that the dielectric response method can effectively assess the status of oil-paper insulation, and the influence of oil gap on the test results is less than 10%.

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“…As we mentioned earlier, obtaining result (8) is an elementary exercise once the voltage on the sensor/sample interface is known so that V, are known for all n. Note that not all periodic voltage profiles 1s JsLff (9) are allowed on this interface, and the method of measurement, sensing electrode short-circuit mode or floating voltage mode, will affect the voltage profile. The electric field across the interface must satisfy the continuity equation (neglecting surface effects here)…”

Section: The Continuum Modelmentioning

confidence: 99%

“…Our research group has been developing interdigital sensors primarily for monitoring moisture dynamics in transformer insulation for the purpose of better understanding the 'flow electrification' failure mechanism [8,9].…”

mentioning

confidence: 99%

Forward and inverse parameter estimation algorithms of interdigital dielectrometry sensors

Lesieutre

Mamishev

et al. 2001

IEEE Trans. Dielect. Electr. Insul.

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In this paper we extend the continuum model for interdigital dielectrometry sensors and propose a new, direct technique for estimating material electrical properties from measurements. Interdigital sensors consist of alternating pairs of long, thin electrodes on a plane. An ideal model assumes that the periodic structure extends to infinity and the electrodes have no thickness. We extend this ideal analysis to account for the physical thickness of the electrodes. We also present the model in a matrix form which is amenable to linear algebraic analysis techniques. In particular, the 'inverse problem' of estimating material properties is formulated as a generalized Eigenvalue problem, which avoids the convergence problems of previous iterative algorithms.

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Moisture dynamic measurements of transformer board using a three-wavelength dielectrometry sensor

Cited by 11 publications

References 6 publications

Moisture equilibrium in transformer paper-oil systems

Moisture equilibrium in transformer paper-oil systems

The assessment of oil-paper insulation condition based on frequency response method

Forward and inverse parameter estimation algorithms of interdigital dielectrometry sensors

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