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Erosion by partial discharge and layer effect on breakdown characteristics of polymeric films immersed in cryogenic fluid were examined. The results obtained are following.
Liquid insulation occupies a key position in the range of electrical insulating materials. We can conceive of a volume of empty space to which matter is added, molecule by molecule, until the vacuum is transformed, in stages through low pressure gas, high pressure gas, liquid of low viscosity, liquid of high viscosity, to an amorphous solid. First assumptions might be that as the phase changes then...
The knowledge of the local electrical field in the immediate vicinity of the electrode surface is very desirable if one were to understand the charge injection process at an electrode. Many attempts have been made to determine this local field experimentally.[1,3] None of these attempts has so far succeeded in estimating the field in front of the primary streamer which is formed as a result of the...
Electron transport behaviour in liquid argon has been studied using a Monte Carlo method in which the differential cross section defined by Van Hove for the interaction of an electron with liquid atoms is considered instead of two mean free paths, A1 and A0 of Cohen and Lekner. The drift velocity and mean energy of electrons for field strength between 1 and 10 kV/cm are in good agreement with those...
Dielectric Relaxation studies on heterocyclic compound benzothiazole and 2-Methylbenzothiazole are somewhat inadequate. Benzothiazole contains a five membered heterocyclic thiazole ring fused with benzene. In addition to having pharmacological importance, it is used in the preparation of dyes. Their comparative study may reveal some molecular properties containing fused ring systems.
The results are given of experimentation carried out to determine the decrease in the frequency and intensity of the light pulses associated with partial discharges (PDs) in specimens of hexadecane both pure and containing diphenyl, benzophenone, and anthraquinone. It was shown by gas chromatography (GC) that for the same applied voltage, hexadecane containing an additive displays more resistance...
Liquid or supercritical helium is the basic insulant for superconducting devices. Many efforts have been taken to find out its dielectric strength under various conditions. Paschen's law has been found valid in helium gas down to very low temperatures, as far as the field strength does not exceed 15 to 20 kV/mm1. In liquid and supercritical helium the situation is more complex. Often a large statistical...
The application of high electrical fields to a liquid dielectric induces internal pressures. These internal pressures have been the subject of numerous investigations [1–5].
The use of electric fields in order to increase heat transfer in fluids dates back some time. One part of the previous work deals with the effects of the dielectric forces resulting from permittivity gradients which are themselves induced by the imposed temperature gradients [ 1, 2, 3]. The rest of the work is concerned with the Coulomb force which the electric field (E) exerts on the free charge...
As a result of our experiment the following outcomes are to be made: If c > 0.6 (x > 0.2) no spontaneous crystallization occurs and if c < 0.4 (x < 0.12) only the maximum of density is detected and for this concentration range crystalsization occurs always at temperatures higher than − 40°C. The replacement of 12 % water molecules by glycerol molecules seems sufficient for destroying the...
This Part of the paper is devoted to the constitutive distributed parameter description of the generation and phenomenal aspects of the multipartial electric fields in the fluid phase.
The conduction band energy Vo and the electron mobility u in n-, isobutane (n-C4, i-C4), n- and isopentane (n-C5, i-C5) fluids were measured as a function of density N in order to examine the effect of molecular structure on the electronic behaviour in nonpolar fluids. Vo values were determined by photoelectric work function measurements. u values were determined by a time-of-flight methods. The apparatus...
The properties of the primary charge carriers formed on ionization of saturated hydrocarbon liquids have been found to display a marked sensitivity to the structure of the individual molecules of the medium. Thus for excess electrons the mobility has been shown to be dramatically influenced by the degree of sphericity of the molecules. For electron holes (solvent radical cations) a high mobility has...
Samples of two types of insulating oil used in transformers and switch-gear components in Egypt are experimentally tested to determine the breakdown-change of their dielectric constant and of their breakdown voltage. A standard oil tester is used to apply high voltage to the samples at two different rates and two different time intervals. The breakdown voltage of each sample is measured at the two...
All the measurements performed in the course of this study show that the oil aged up to the end of its induction period and reclaimed, is the only one whose oxidation resistance and characteristics in general were as good as that of the reference naphthenic oil used. From a practical point of view, transformer oils should not be allowed to age after their induction period, which can be determined...
Particle deposition occurs very rapidly and it modifies significantly the breakdown voltage and the metals content of transformer oil. This leads to unrealistic values not representative of the oil's condition in the transformer. It has been shown that particles in oil homogenization can be successfully achieved by 25 min of ultrasonic agitation for a I-liter volume of oil. This simple, rapid and...
We have proposed the model of prebreakdown processes in liquids under pulse voltage. Physical estimation of prebreakdown process parameters leads to obtaining a new approximate formula for pulse electrical strength calculation. This expression can be used for explanating Dg the main regularities of breakdown including those which are not described in this paper, for example E (γ), E (T) where γ is...
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