Effects of frequency, temperature, compression, and air pressure on the dielectric properties of a multilayer stack of dry kraft paper

Morgan, V.T.

doi:10.1109/94.660818

Cited by 51 publications

(26 citation statements)

References 14 publications

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“…One of the reasons is that NFC modified presspaper has a higher density. According to [32], dielectric loss is partly due to the decreased DC volume resistivity. Relative permittivity of presspaper containing NFC tends to be higher than that of reference presspaper.…”

Section: Volume Resistivity and Dielectric Responsementioning

confidence: 99%

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Enhancing Insulating Performances of Presspaper by Introduction of Nanofibrillated Cellulose

et al. 2017

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This study explores the possibility of enhancing both mechanical and breakdown properties of insulating presspaper by the introduction of an organic nano additive. Four different concentrations of nanofibrillated cellulose (NFC) were taken into account: 0.5 wt %, 2.5 wt %, 5 wt %, and 10 wt %. Presspaper containing no NFC was also prepared as a reference. Obtained samples were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Mechanical properties and breakdown behaviors were measured. Results show that the addition of 10 wt % NFC to softwood fibers can achieve the best performance. Tensile strength of reference presspaper is 109 MPa, whereas that of presspaper modified by 10 wt % NFC is 136 MPa, resulting in a 25% increase. The improved tensile strength can be attributed to the increased density and inter fiber bond strength. More importantly, presspaper reinforced by 10 wt % NFC can also achieve enhanced AC and DC breakdown strengths, which are 19% and 21% higher than those of the reference presspaper. It is concluded that NFC is likely to be a promising nano additive for cellulose insulation.

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Section: Volume Resistivity and Dielectric Responsementioning

confidence: 99%

“…At 50 Hz, εf is assumed to be 6.5, and εa is regarded as 1 [32]. Because θf is proportional to density, a higher density will result in a higher θf, and therefore increase the relative permittivity of presspaper sample.…”

Section: Breakdown Behaviormentioning

confidence: 99%

Enhancing Insulating Performances of Presspaper by Introduction of Nanofibrillated Cellulose

et al. 2017

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“…These diagnostic techniques include fault gas analysis, moisture analysis, dielectric monitoring, UHF sensors, acoustic sensors, off line or on line PD testing, dielectric response measurements, time response dielectric spectroscopy, dielectric discharge method and return voltage measurement, interpretation of measurements, transfer function analysis and expert system diagnostic software. The phenomenon of understanding the ageing of Kraft paper insulation shows that paper degradation is the cause of production of furan based aldehydes or hydrocarbon gases produced in mineral oil which results in change in DP (degree of polymerization) of cellulose in insulating paper or effect of various parameters using electrical, mechanical and chemical techniques is evaluated which are relevant to assess the state of both paper and oil insulation with identifying its effective life [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Thermal degradation of Kraft paper is caused due to increase in operating temperature so this insulating paper is thermally upgraded to neglect the aging by treating it with additional additives which result in formation of a new modified insulating paper such as amine modified Kraft paper, cyan ethylated paper, and carbamate modified paper by chemical modification for better performance and some other alternative oils are used as a substitute to mineral oil like alkyl-naphthalene oil, vegetable oil to increase the life of oil-paper insulation [21][22].…”

Section: Liquid Oil Insulation:-mentioning

confidence: 99%

A Review of Condition Monitoring Assessment of Power Transformers Insulation

Aggarwal¹,

Jindal²,

Singh³

2016

IJAR

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“…When β is close to zero, the Lichtenecker formula is got by expanding the terms with exponents into an infinite series and neglecting the terms of higher order. 4 lnε…”

mentioning

confidence: 99%

“…Relative permittivity and density of cellulose fiber are 6.5 (at 50 Hz) and 1.53 g/cm 3 , respectively. 4,13 Those corresponding to air void are assumed to be 1 and 0 g/cm 3 . Figure 3 shows the comparison of the numerically calculated permittivity values and the analytical solutions for presspaper with a bulk density from 0.7 g/cm 3 to 1.2 g/cm 3 .…”

mentioning

confidence: 99%

Modeling of the effective permittivity of insulating presspaper

et al. 2016

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Effective permittivity model of insulating presspaper is built on the basis of the microstructure of the material. Due to the essentially layered structure in z-direction of presspaper, air voids inside the mixture can be treated as right prismatic inclusions. Analytical formula for the prediction of the effective permittivity of insulating presspaper is derived. Interestingly, the derived formula equals to the mixing equation applied for dielectrics in series. Numerical simulation was used to validate the analytical results by considering the air voids as cubical inclusions. Results show a good agreement between the analytically and numerically calculated effective permittivity values. Furthermore, dielectric permittivity results of commercial kraft paper and laboratory-made presspaper at 50 Hz were measured and compared with modeled data. It turns out that the deduced results give a good accuracy for the effective permittivity determination.

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Effects of frequency, temperature, compression, and air pressure on the dielectric properties of a multilayer stack of dry kraft paper

Cited by 51 publications

References 14 publications

Enhancing Insulating Performances of Presspaper by Introduction of Nanofibrillated Cellulose

Enhancing Insulating Performances of Presspaper by Introduction of Nanofibrillated Cellulose

A Review of Condition Monitoring Assessment of Power Transformers Insulation

Modeling of the effective permittivity of insulating presspaper

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