The velocity of drying of the already impregnated oil-paper insulation

Nikoloski, L.

doi:10.1109/icpadm.1997.617642

Cited by 3 publications

(2 citation statements)

References 2 publications

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“…Paper is not only characterized by its low cost, but its structure permits an association with impregnating oil. This oil impregnation leads to a compound, revealing an excellent insulating behavior [1]. However, the presence of humidity drastically affects the properties of this compound.…”

Section: Introductionmentioning

confidence: 99%

Experimental Approach of Dielectric Losses Measurement in Insulating Paper under Distorted Voltage Stress

Megherbi

Bitam-Megherbi

Benamrouche

2009

Electric Power Components and Systems

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The present work describes an experimental investigation dealing with the harmonic distortion of the voltage applied to samples of pressboard paper. The investigation especially concerns the study of dielectric losses in order to determine the contribution of each component in these losses. The influence of the moisture level of the samples is also discussed with respect to the influence of the humidity on the insulating system. A new method of determining the losses is proposed; it permits the weighing of the contribution of each harmonic. Three different power supplies with different distortion rates were used in this work. For each experiment, the form and the RMS value of the current and the voltage are reported. The harmonic analysis was carried out, and the results show an important effect of the distortion rate on the voltage and the moisture level on the dielectric losses.

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Section: Introductionmentioning

confidence: 99%

Experimental Approach of Dielectric Losses Measurement in Insulating Paper under Distorted Voltage Stress

Megherbi

Bitam-Megherbi

Benamrouche

2009

Electric Power Components and Systems

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“…Therefore, the decision to continue or to stop the transformer exploitation is closely dependent on a perfect knowledge of the moisture levels [7][8][9][10][11][12][13]. Because of the effect of moisture on the insulation's global behavior several researchers undertook studies on the subject.…”

Section: Introductionmentioning

confidence: 99%

A Recovery Voltage as non-Destructive Tool for Moisture Appreciation of Oil Impregnated Pressboard: An Approach for Power Transformers Testing

Bitam-Megherbi¹,

Megherbi²,

Mammeri³

2013

ijeei

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This paper is devoted to recovery voltage as a diagnostic non destructive method for an assessment of an insulating state of power transformers. The insulating pressboard used in power transformers is tested for different moisture levels. Experiments were carried out with samples from the same material intended to power transformers building. A charge and discharge of a capacitor having pressboard paper as dielectric is a suitable tool for an appreciation of the polarization and relaxation processes. The polar character of the water's molecules has an influence on the permittivity. Then the polarization of the paper will be affected by a moisture presence. Time evolution of the recovery voltage for different durations of the charges was examined. An increase of the recovery voltage with the moisture content was observed. The maximum of recovery voltage occurs much later starting from the moment of the opening of the circuit for higher moisture for all examined levels. Thus, the time separating the short circuit and the maximum's occurring can be considered like an important parameter allowing an appreciation of the moisture state of oil impregnated paper.

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Process Modeling and Optimization Studies in Drying of Current Transformers

Bhattacharya¹,

D’Melo²,

Chaudhari³

et al. 2012

Transactions on Electrical and Electronic Materials

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understanding of the drying mechanism involved and also to predict the water collection rates . A molecular as wellas macroscopic approach was adopted for the prediction of drying rate. Ficks law of diffusion was adopted for theprediction of drying rates at macroscopic levels. A steady state and dynamic mass transfer simulation was performed.The bulk diffusion coefficient was calculated using weight loss experiments. The accuracy of the solution was a strongfunction of the relation developed to determine the equilibrium moisture content. The actually observed diffusionconstant was also important to predict the plant water removal rate. Thermo gravimetric studies helped in calculatingthe diffusion constant. In addition, simulation studies revealed the formation of perpetual moisture traps (loops)inside the CT. These loops can only be broken by changing the temperature or pressure of the system. The changein temperature or pressure changes the kinetic or potential energy of the effusing vapor resulting in breaking of theloop. The cycle was developed based on this mechanism. Additionally, simulation studies also revealed that theactual mechanism of moisture diffusion in CT’s is by surface jumps initiated by surface diffusion balanced against thesurrounding pressure. Every subsequent step in the cycle was to break such loops. The effect of change in drying timeon the electrical properties of the insulation was also assessed. The measurement of capacitance at the rated voltageand one third of the rated voltage demonstrated that the capacitance change is within the acceptance limit. Hence,the new cycle does not affect the electrical performance of the CT

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The velocity of drying of the already impregnated oil-paper insulation

Cited by 3 publications

References 2 publications

Experimental Approach of Dielectric Losses Measurement in Insulating Paper under Distorted Voltage Stress

Experimental Approach of Dielectric Losses Measurement in Insulating Paper under Distorted Voltage Stress

A Recovery Voltage as non-Destructive Tool for Moisture Appreciation of Oil Impregnated Pressboard: An Approach for Power Transformers Testing

Process Modeling and Optimization Studies in Drying of Current Transformers

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