Temperature and moisture transient flow electrification measurements of transformer pressboard/oil insulation using a Couette facility

Washabaugh, Andrew; Guggenberg, P.A. von; Zahn, M.; Melcher, James R.

doi:10.1109/icpadm.1991.172206

Cited by 15 publications

(10 citation statements)

References 8 publications

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“…However, from an algebraic inversion of ( 3 ) , the correct pressure relation is: pv = 9.2683 x 1 O9 x c1.4959 x e(-7069iTJ, (5) which significantly differs from (4). It appears that the derivation of (4) from ( 3 ) had an algebraic error.…”

Section: E~u~l I B R I U~ Curves For Water Vapor Pressure and Moistwementioning

confidence: 92%

“…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].…”

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confidence: 99%

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Moisture equilibrium in transformer paper-oil systems

Zahn²,

Lesieutre³

et al. 1999

IEEE Electr. Insul. Mag.

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330

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: E~u~l I B R I U~ Curves For Water Vapor Pressure and Moistwementioning

confidence: 92%

mentioning

confidence: 99%

Moisture equilibrium in transformer paper-oil systems

Zahn²,

Lesieutre³

et al. 1999

IEEE Electr. Insul. Mag.

Self Cite

330

135

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show abstract

“…The migration of small amounts of moisture from paper to oil has been associated with the phenomenon of static electrification appearing when there is a charge accumulation on the interfaces between dry and humid zones [12] [13]. Moisture transfer can be activated by moisture concentration gradient, temperature gradient and pressure gradient [13]. In addition dissolved moisture in oil can precipitate out during rapid cool down periods and become free water which may or may not re-dissolve [14].…”

Section: Moisture Contentmentioning

confidence: 99%

Impact of Accelerated Stresses on Power Transformer Insulation

Singh¹,

Sood²,

Verma³

2017

EPE

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The paper is based on the experimental investigation of accelerated stresses on insulation of power transformer. The effects of individual thermal and electrical stresses have been graphically presented. The factors accelerated thermal aging factor (ATAF) and accelerated electrical aging factor (AEAF) have been introduced, it helps to understand the contribution of thermal and electrical stresses and degradation trends of insulating properties. The accelerated aging factors have been mathematically correlated with different properties of insulation such as moisture, breakdown voltage (BDV), tan delta and resistivity. These parameters were determined experimentally for fresh oil samples and for samples subjected to accelerated aging.

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“…An important application of this technology that is currently under investigation is the ability to study moisture dynamics in power transformer insulation materials in order to prevent failures due to free water formation, excessive losses, and dielectric breakdown induced by flow electrification [9,13,22,23].…”

Section: Motivationmentioning

confidence: 99%

Evaluation of diffusion-driven material property profiles using three-wavelength interdigital sensor

Mamishev

Bau

et al. 2001

IEEE Trans. Dielect. Electr. Insul.

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The response of a three-wavelength interdigital dielectrometry sensor to the moisture diffusion process in oil-impregnated transformer pressboard has been simulated using an empirical relationship between the moisture concentration and the dielectric properties of the pressboard. A benchmark test of the moisture diffusion process has been developed with the purpose of comparing alternative parameter estimation algorithms used in w-lc (frequency wavenumber) dielectrometry. The results of simulations highlight characteristic features of the multi-wavelength sensor respon e delay from the start of the transient moisture diffusion process ngth, the influence of moisture boundary conditions, and the r nitude and variations of dielectric properties. One of the parameter estimation algorithms, linear calibrated admittancebased estimation (LCABE), has been applied to both simulated and measured data. Adequate performance of the LCABE approach in the absence of strong ,discontinuities of dielectric properties in the electric field penetration region is demonstrated and contrasted to an electrically shielded region case, in which the signal response becomes nonlinear. The proposed approach offers significant potential for the measurement of diffusion processes in various dielectrics, especially for cases with highly irregular geometry or material structure. Measurement results from moisture diffusion process monitoring are included. Parameter estimation of measurement results with LCABE confirm its applicability to the monitoring of moisture dynamics in transformer pressboard.

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Temperature and moisture transient flow electrification measurements of transformer pressboard/oil insulation using a Couette facility

Cited by 15 publications

References 8 publications

Moisture equilibrium in transformer paper-oil systems

Moisture equilibrium in transformer paper-oil systems

Impact of Accelerated Stresses on Power Transformer Insulation

Evaluation of diffusion-driven material property profiles using three-wavelength interdigital sensor

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