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Liquid dielectric

About: Liquid dielectric is a research topic. Over the lifetime, 3702 publications have been published within this topic receiving 45150 citations.


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Journal ArticleDOI
TL;DR: The nonlinear dynamics of the free surface of an ideal dielectric liquid in a strong electric field is studied in this article, where an equation for the evolution of surface electrohydrodynamic waves is derived in the approximation of small surface-slope angles.

34 citations

Journal ArticleDOI
TL;DR: In this paper, Sorensen et al. make a plea for a more strenuous use of insulating materials, in the light of a request in another paper given this morning, in which the author recommends a decrease in the test voltage applied to transformers with one terminal grounded.
Abstract: R. W. Sorensen: My first point is in connection with the statement that we use our insulations under stresses which rarely exceed the breakdown voltage of air, though tests show a strength of 10 to 20 times that of air for many of the insulations used. This plea for a more strenuous use of insulating materials is interesting in the light of a request in another paper given this morning, in which the author recommends a decrease in the test voltage applied to transformers with one terminal grounded.

34 citations

Journal ArticleDOI
TL;DR: The capillary-dominated regime of dynamics of electrified jets of a viscous leaky dielectric liquid is studied numerically and the power-law dependences of the jet radius and electric current on the parameters of the problem are given.
Abstract: The capillary-dominated regime of dynamics of electrified jets of a viscous leaky dielectric liquid is studied numerically. In this regime the effective force in the direction of an applied field due to tangential electric stresses is balanced by the gradient of liquid pressure governed by the surface-tension stresses. As is characteristic of this regime, the electric current and the characteristic jet radius are dependent on the surface-tension coefficient and not on viscosity. In the scope of this work, the conditions of the existence of this regime are determined. A qualitative order-of-magnitude analysis gives the power-law dependences of the jet radius and electric current on the parameters of the problem (conductivity, applied electric field, flow rate, and surface-tension coefficient). Numerical results are obtained for low conductive liquids for a large range of the dimensionless flow rate (capillary number, Ca). The order-of-magnitude estimations of electric current are in agreement with the numerical results given a small Ca. The corresponding numerically obtained jet shapes are discussed and explained.

34 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of the type of solid insulating material, in contact with the streaming oil, on the ECT (electrostatic charging tendency) of transformer oil is investigated using different types of oils and solid materials.
Abstract: Due to increased demand of electrical power, the trend of the capacity and voltage rating of power transformers increases with reliable design; especially in large oil-cooled power transformers. Consequently, the use of polymer blended and polymer coated insulations in such transformers are the most recent advances in modern technology. The consequences of the type of solid insulating material, in contact with the streaming oil, on the ECT (electrostatic charging tendency) of oil are the principal aim of this paper. ECT of transformer oil is experimentally investigated using different types of oils and solid insulting materials. Two laboratory analog cycles are used; namely, a closed and an open cycle. In the closed cycle, the investigated factors are the type and polarity of the applied voltage (/spl plusmn/10 kV and 10 kV/sub rms/ at 50 Hz), solid insulating material (polymeric and non-polymeric insulation), and oil type, temperature (20 to 70/spl deg/C) and velocity (1.5 to 3.25 m/s). Good agreement is achieved between the measured data under ac and dc voltages of both the conduction and streaming currents, and the derived formulas. The currents increase exponentially with oil temperature, velocity and applied voltage. All solid dielectrics used show quantitative as well as qualitative changes in oil electrification especially at low temperatures. In the open cycle, both the rotating cylinder speed (430 rpm) and the oil volume are kept constant, and the oil temperature is raised to 120/spl deg/C for different types of oils and solid dielectrics. ECT depends on the oil type and is activated with temperature. Cellulose-based dielectrics give the highest ECT and coating of these dielectrics with epoxy resin enhances the ECT. Different suppression characteristic is obtained using Theophylline in different fresh oils.

34 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202328
202267
202191
2020122
2019142
2018120