A review of moisture diffusion coefficients in transformer solid insulation-part 1: coefficients for paper and pressboard

García, Diego; García, Belén; Burgos, Juan Carlos

doi:10.1109/mei.2013.6410539

Cited by 40 publications

(33 citation statements)

References 15 publications

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“…Moreover, according to [16][17][18], the thickness of the cellulose materials also strongly affects the process of water migration. In a brochure [17], distinguishing the insulating system components into three insulation structures such as: "thick structures", "thin and cold structures" and "thin and hot structures" can be found.…”

Section: Water Migration In An Oil-paper Insulation System In the Conmentioning

confidence: 99%

Moisture Migration in an Oil-Paper Insulation System in Relation to Online Partial Discharge Monitoring of Power Transformers

2016

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Most power transformers operating in a power system possess oil-paper insulation. A serious defect of this type of insulation, which is associated with long operation time, is an increase in the moisture content. Moisture introduces a number of threats to proper operation of the transformer, e.g., ignition of partial discharges (PDs). Due to the varying temperature of the insulation system during the unit's normal operation, a dynamic change (migration of water) takes place, precipitating the oil-paper system from a state of hydrodynamic equilibrium. This causes the PDs to be variable in time, and they may intensify or extinguish. Studies on model objects have been conducted to determine the conditions (temperature, humidity, time) that will have an impact on the ignition and intensity of the observed phenomenon of PDs. The conclusions of this study will have a practical application in the evaluation of measurements conducted in the field, especially in relation to the registration of an online PD monitoring system.

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Section: Water Migration In An Oil-paper Insulation System In the Conmentioning

confidence: 99%

Moisture Migration in an Oil-Paper Insulation System in Relation to Online Partial Discharge Monitoring of Power Transformers

2016

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“…It was shown in part one of this article [11] that several researchers obtained coefficients for paper or pressboard, while others proposed curves or equations that can be used to simulate moisture dynamics in transformer insulation, and a summary is shown in Table 2. Most of the available coefficients are based on the empirical equation (6) proposed by Guidi [5].…”

Section: Resultsmentioning

confidence: 99%

“…As described in part one of this article [11], the diffusion coefficient of cellulosic insulation depends on moisture concentration, giving a nonlinear second-order differential equation. To solve this equation, the finite element method was applied by using Comsol Multiphysics …”

Section: Diffusion Modelmentioning

confidence: 99%

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A review of moisture diffusion coefficients in transformer solid insulation - Part 2: Experimental validation of the coefficients

García

Villarroel

García

et al. 2013

IEEE Electr. Insul. Mag.

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“…To attain this result, transformer manufacturers dry their paper under a vacuum (<1 mbar) at temperatures between 85 • C to 130 • C, for a period ranging from several days to two or three weeks before impregnation, depending upon the size of the transformers [5][6][7][8]. This operation aims to remove water vapor and air in the paper interstices before the impregnation process [9]. Drying allows for the reduction of the water content in the solid insulation to a level of 0.25% or less.…”

Section: Introductionmentioning

confidence: 99%

Modeling the Insulation Paper Drying Process from Thermogravimetric Analyses

et al. 2018

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Abstract:It is now well-established that moisture in the oil paper insulation used in power and instrument transformers significantly reduces the transformers' lifetimes, and can eventually lead to premature failure. This moisture should, therefore, always be removed, not only during production but also after repairs. At the final stage of manufacturing, the drying process should be carried out to remove water and air vacuoles contained in the cellulose-based paper before impregnation. Successful drying helps increase the residual life of transformers, because the presence of moisture and air vacuoles accelerates the aging/degradation process of the oil paper insulation. Proper estimation of residual moisture before impregnation and the determination of the time required for drying play key roles in the time-consuming process of drying. In this paper, the disadvantages of inadequate drying are addressed, followed by a mathematical approach to model the paper drying process. A mathematical model describing the kinetics of drying according to temperature, initial moisture, paper weight, final moisture, and extraction rate is proposed. This model also estimated the amount of moisture removed at the end of the drying process.

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A review of moisture diffusion coefficients in transformer solid insulation-part 1: coefficients for paper and pressboard

Cited by 40 publications

References 15 publications

Moisture Migration in an Oil-Paper Insulation System in Relation to Online Partial Discharge Monitoring of Power Transformers

Moisture Migration in an Oil-Paper Insulation System in Relation to Online Partial Discharge Monitoring of Power Transformers

A review of moisture diffusion coefficients in transformer solid insulation - Part 2: Experimental validation of the coefficients

Modeling the Insulation Paper Drying Process from Thermogravimetric Analyses

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