Showing papers on "Liquid dielectric published in 1979"

The effect of temperature-induced variations in charge carrier mobility on a stationary electrohydrodynamic instability

Abstract: An externally applied d.c. electric field is known to produce instability in a plane layer of dielectric liquid heated from above. The stationary linear instability of a unipolar charge injection equilibrium for which carrier mobility depends linearly on temperature is investigated. It is found that the sign of the temperature gradient in relation to the emitting electrode determines whether or not such instability can occur, and that two types of instability can be distinguished: (i) a space charge modified Benard mode; and (ii) a thermally modified space charge mode. It is shown that the critical voltage is highly dependent upon the absolute value of mobility and its variation across the layer.

Electrohydrodynamic Instability in a Viscoelastic Liquid Layer

Abstract: The problem of the onset of instability in a horizontal layer of viscoelastic dielectric liquid under the simultaneous action of a vertical ac electric field and a vertical temperature gradient is analyzed. Applying linear stability theory, an equation of eighth order is derived. Under somewhat artificial boundary conditions, this equation can be solved exactly to yield the required eigenvalue relationship from which various critical values are determined in detail. It is shown that oscillatory modes of instability exist only when the thickness of the liquid layer is smaller than about 0.5 mm and for such a thin layer the force of electrical origin is much more important than buoyancy force.

On the High Frequency Dielectric Behavior of Castor Oil

Abstract: The low frequency dielectric behavior of castor oil (a vegetable oil) has been analyzed quite exhaustively in the context of its application as impregnant in capacitors. For the sake of completeness and in order to understand the relaxation phenomena in this liquid dielectric, this high frequency dielectric study was undertaken. In order to compare its properties with a liquid dielectric used in similar application and whose high frequency behavior has been quite well analyzed, Arochlor 1476 was studied. It is observed that both liquids have distributed relaxation times. The distribution parameters together with the two distinct relaxation times have been calculated by measuring the average relaxation time. It has been found that the distinct relaxation times thus calculated represent the dielectric behavior quite satisfactorily. The average dipole moments, dipole radii and thermal activation energies for dipole relaxation have also been evaluated.

Electrical capacitor having an improved dielectric system

Abstract: An electrical capacitor having an improved dielectric system. The capacitor includes layers of metal foil and a dielectric sheet material which is impregnated with a liquid dielectric composition composed of a mixture of methyl diphenyl ethane and a lower alkyl diphenyl.

Ozone production apparatus

Abstract: Ozone is produced when oxygen dissolved or absorbed in an inert liquid dielectric is irradiated with ultra violet (light) energy in the wave length range between 1100 and 2200 angstrom units. The apparatus wherein oxygen gas or air or mixtures thereof, converts a percentage of the oxygen to ozone is composed of special ultra violet 1100 to 2200 angstrom wave length transmitting glass or plastic liquid retainer structural material for the selected inert dielectric liquid used as the absorber liquid for the oxygen, air and ozone gases. The configurations for construction of the apparatus are adinfinitum as flat parallel sheets, paired-corrugated sheets, concentric tubes, etc., any of which control the thickness of the dielectric liquid passing by the source of irradiation.

Maxwell-Wagner Dielectric Polarization in Polypropylene Film/Aromatic Dielectric Fluid System for High Voltage Capacitor Use

Abstract: The chemical interaction between biaxially-oriented polypropylene film and diarylalkane has been investigated by studying the dielectric properties of the polypropylene film impregnated by the fluid. It was found that the s dispersion in its dissipation factor-temperature relationship is related to the segmental motion of the amorphous phase existing in the film, and that the a dispersion is connected with the Maxwell-Wagner type dielectric polarization at the surface of the crystalline phase in the film. Furthermore, it was demonstrated that the dissipation factor at the s dispersion temperature correlates well with the dissolution of the film into the fluid, and that the dissipation factor at the a dispersion temperature correlates closely with the oil absorption of the film immersed in the fluid.

Circular electric mode microwave window

Abstract: For conducting very high microwave power at very high frequencies, circular waveguide transmitting a circular-electric-field mode is used. The vacuum-tight window of an electron tube is often the element with lowest power-handling capability. The inventive window has two dielectric plates with a space between them. There is a gap in the waveguide inner wall through which a dielectric fluid is circulated between the plates to cool them. The gap leads to a region containing wave-absorbing material such as water to absorb modes other than the circular-electric-field mode.

Method and apparatus for hydrogen production in an absorber liquid by electrochemical of coal and water

Abstract: Coal and carbon particulates or dust when mixed with water through which a direct electric current passes, electrochemically react reducing the water to hydrogen and the coal to carbon dioxide. By washing the electrodes with an inert dielectric liquid the gases as formed are mechanically washed from both the anode and cathode electrodes and subsequently absorbed by the liquid thus more efficiently keeping the chemical reaction proceeding to the right. By using a liquid dielectric capable of operating under elevated temperatures and superatmospheric pressures the chemical reactions proceed at a much greater rate than at atmospheric and ambient conditions. This disclosure teaches the art and science of producing hydrogen by reacting coal or carbon dust with hot water retained as water by superatmospheric pressure. The pressure controlled by the use of an inert dielectric liquid which washes the electrodes and while doing so depolarizes them by absorption of the gases. Gases are recovered from the absorber liquid for use.

Dielectric corona rings

Abstract: A dielectric corona ring to provide field shaping by spreading or deconceating an electric field for reduction or elimination of ionization of air near a high voltage insulator.

Model for breakdown process in dielectric discharges

Abstract: A heuristic model to explain the blowoff of charge during an electron-induced dielectric discharge is presented. It is proposed that blowoff of charge is initiated by a punchthrough or a flashover. The discharge time is assumed to be governed by an LC time constant where L is the inductance of the electrons flowing in the branches of the Lichtenberg figures at an electron range below the irradiated surface and C is the capacitance between the trapped electrons and the substrate for the discharged area. Experiments to verify that blowoff is a consequence of punchthrough or flashover and to measure the punchthrough current and the variation of discharge time with the sample area and thickness were conducted.

Fuel cell use of gaseous fuels and oxygen provided at electrode absorbed in liquid dielectric

Abstract: A fuel cell is an electrochemical device composed of a nonconsumable anode and cathode, an electrolyte, fuel and controls, the maximum current density that can be passed depends upon the rate of mass transfer of atoms and their respective electrons. This invention improves the rate of mass transfer by submerging the "oxygen" contact electrode in a dielectric liquid saturated with absorbed oxygen, and when using a gaseous fuel, submerging the "hydrogen" contact electrode in a dielectric liquid saturated with the absorbed gaseous fuel. The invention uses a liquid dielectric which is nonmiscible with water, thus as water is formed at either electrode, the water is immediately rejected from the electrode/dielectric contact and being equally rejected by the dielectric is removed from interfering or resisting current flow, thus further improving the efficiency of the fuel cell.

Level sensing device for dielectric liquids

Abstract: A device (1) for sensing the presence of a dielectric liquid at a predetermined level in a tank is described. The main feature of device (1) is that it comprises a first and a second bimetallic strip (23, 44) disposed facing each other and a resistor (48) disposed in proximity to said second strip (14) at a level in said tank equal to said predetermined level.

Apparatus for processing an electrical apparatus

Abstract: An apparatus for processing an electrical apparatus, such as a capacitor, containing a polymeric dielectric material. The interior of the capacitor casing, which is at room temperature, is initially connected to a vacuum source to evacuate the interior of the casing and when a vacuum sensing unit indicates that the required vacuum has been obtained, a degassed dielectric liquid is supplied to the interior of the casing. A positive pressure is applied to the liquid in the casing to fully impregnate the polymeric layer. When the desired capacitance is obtained, the impregnation is complete and the unit is sealed.

The Effects of Dielectric and Soil Nonlinearities on the Electromagnetic Transient Response of Cables Lying on the Surface of the Earth

Abstract: In this paper, a method of including nonlinear breakdown of the cable dielectric and the soil for an insulated cable lying on the surface of the earth is presented The resulting nonlinear model is then applied to the problem of a surface cable illuminated by an electromagnetic pulse from a nuclear burst The results of this study show that the nonlinear effects can greatly increase the peak amplitude and the late time response of the induced current, but the peak voltage is reduced It was found that the cable dielectric breakdown was more important than the soil breakdown insofar as influencing the response

Development And Reliability Study On High Voltage RCP-XLPE Cables

Abstract: The electrical qualities of recent RCP-XLPE cables, manufactured under the radiant curing process, will be presented in this paper. These can be satisfactorily used as high voltage cables of the 275 kV class. In order to obtain a still higher reliability of the cables, the statistical method is studied. A fundamental theory on the AC voltage full reel test is proposed and verified experimentally. According to our theory a higher test voltage assures higher reliability in service. Since a stress as high as 40 kV/mm does not do any damage to the insulation of RCP-XLPE cables, they can be assured to have a still higher reliability by a higher voltage reel test. An example of the effect of the reel test in actual is calculated, which shows that the failure probability in service rapidly decreases as the test voltage becomes more than twice the operating voltage.

Power circuit interrupter

Abstract: A circuit interrupter employing a liquified dielectric medium such as sulfur hexafluoride. A pump cylinder (74) forces the dielectric liquid into the vicinity of a fixed contact (50). The pump cylinder is refilled from within the contact enclosure (44) after each current interruption to allow for repeated operations. Check valves (88, 92) are provided to prevent any dielectric gas from entering the pump cylinder. The interrupter system further includes a pressure absorbing accumulator (95-97) and a cooler.

Hydromagnetic interaction in a fluid dielectric

Abstract: It is shown that a dielectric fluid is capable of hydromagnetic interaction, much like a conducting fluid. The physical principle of this interaction is outlined and the criteria for dominance of the interaction are derived.

Instruments to measure the salient properties of fluid dielectrics

Abstract: A range of compact portable instruments has been developed to diagnose and quantify changes in fluid dielectrics in order to maintain them in a satisfactory condition. The degree of moisture saturation (RH) of a liquid dielectric can be used to assess its condition and that of the associated solid insulation and the RH meter measures this value directly. The Karl Fischer instrument measures the actual quantity of water present in parts per million and the Oxidation meter determines the degree of thermal aging of the fluid that has occurred. Any gasses evolved by the dielectric due to hot spots, arcing or partial discharges can be identified and quantified by using the gas analyser unit.

Diaphragm having a pattern of reduced thickness in a high voltage, circuit-interrupting device

Abstract: An improved circuit-interrupting device of the type which includes an arcing rod which is moved away from a stationary contact in response to an overcurrent through the device. The device includes a container of pressurized dielectric fluid having a port from which the fluid is directed at an elongating arc formed between the moving arcing rod and the stationary contact. The device also includes a diaphragm normally contacted by the arcing rod which normally closes the port and restrains arcing rod movement. The improvement includes a pattern of reduced thickness in the diaphragm about the point of contact between the diaphragm and the arcing rod. The pattern may be circular or star-shaped and may be produced by pressing, dieing, stamping, scoring, forming, etching, or coating. Depending on the specific construction of the device, the diaphragm either fuses or melts along the pattern or is ruptured or torn by arcing rod movement following an overcurrent through the device. The pattern ensures that a large opening is formed in the diaphragm to permit the escape from the container of sufficient dielectric fluid to ensure extinguishment of the arc.

Method of de-burring and cleaning electrode systems

Abstract: A method of de-burring and cleaning an electrode system, a printed circuit board, or the like comprising at least two conductors positioned at a predetermined distance from each other by means of insulation material. The electrode system is immersed in a dielectric liquid and an electric potential difference is then applied between the conductors which is sufficiently large to generate an electric flash-over between the conductors. As a result of the small free path length in the dielectric liquid metal sputtered from the conductors can not deposit on the insulating parts of the electrode system.