scispace - formally typeset
Search or ask a question

Showing papers on "Liquid dielectric published in 1975"


Journal ArticleDOI
TL;DR: In this paper, the authors considered two asymptotic states of convection: one where the whole motion is dominated by viscosity, and one where inertial effects dominate, and they derived the dependence of the current density ratio I/I0 on the stability parameter T = M2R = eϕ0/Kρν, and on 1/R = ν/Kϕ 0, which is an equivalent Prandtl number.
Abstract: The problem of electric charge convection in a dielectric liquid layer of high ionic purity, when subjected to unipolar injection, is in many ways analogous to that of thermal convection in a horizontal fluid layer heated from below, although no formal analogy can be established. The problem treated is intrinsically more nonlinear than the thermal problem. We consider two asymptotic states of convection: one where the whole motion is dominated by viscosity, and one where inertial effects dominate. In each state, two or three spatial regions are distinguished. From the approximate equations that hold in the different regions, information about the variation of the different quantities with distance from the injector is obtained, and further approximations permit us to establish the dependence of the current density ratio I/I0 (called the electric Nusselt number) on the stability parameter T = M2R = eϕ0/Kρν, and on 1/R = ν/Kϕ0, which is an equivalent Prandtl number (e is the permittivity, ρ the fluid density, K the mobility, ν the kinematic viscosity, and ϕ0 the applied voltage). In the viscous state, the analysis gives I/I0 ∞ T½; in the inertial state the law I/I0 ∞ (T/R)1/4 = M½ is obtained. Since M is independent of the applied voltage, the latter law shows the saturation in the electric Nusselt number observed in earlier experiments. The transition in the states is associated with a transition number (MR)T [gap ] 30, which is an electric Reynolds number, related to an ordinary Reynolds number of about 10.The experimental results, obtained in liquids of very different viscosities and dielectric constants, verify these theoretical predictions; further, they yield more precise numerical coefficients. As for the transition criteria, the experiments confirm that the viscous and inertial effects are of the same order when Re [gap ] 10. It was also possible to determine roughly the limits of the viscous and inertial states. The viscous analysis remains valid up to a Reynolds number of about 1; the inertial state can be considered valid down to a Reynolds number of 60. Schlieren observations show that the motion has the structure of very stable hexagonal cells at applied voltages just above the critical voltage, which are transformed into unstable filaments when the voltage is increased further. At even higher voltages, the motion finally breaks down into turbulence. It may be of interest to point out that, when M < 3, the electric Nusselt number approaches 1, which is equivalent to the situation in thermal convection at low Prandtl numbers.

196 citations


Journal ArticleDOI
TL;DR: In this article, a Zener diode is used to simulate the corona drop and the buffer dielectric plays a major role in controlling the voltage and the air gap.
Abstract: Electrical characterization is based on a display of voltage and charge which appears as a simple parallelogram. The area is a measure of energy input per cycle and is independent of voltage waveform but very dependent on the maximum voltage. A useful model for such corona discharges employs a Zener diode to simulate the corona drop. The buffer dielectric plays a major roll in controlling the corona power, and the air gap importance depends on the electrode system employed. Proper interpretation of the voltage-charge traces provides insight as to the corona performance and serves as a diagnostic procedure for obtaining optimum performance.

68 citations


Patent
19 Dec 1975
TL;DR: By filling the container of a piezoelectric stack with a dielectric fluid under sufficient pressure, or applying sufficient pressure to a solid dieellectric, to maintain dieelessicle particle velocity and piezelessric particle velocity substantially spaced as mentioned in this paper, the failure of the piezelized stack is prevented.
Abstract: By filling the container of a piezoelectric stack with a dielectric fluid under sufficient pressure, or applying sufficient pressure to a solid dielectric, to maintain dielectric particle velocity and piezoelectric particle velocity substantially spaced, dielectric breakdown with consequent arc over and destruction of the piezoelectric stack is prevented.

59 citations


Journal ArticleDOI
TL;DR: In this paper, the frequency dependence of the conduction anisotropy σ∥−σ⊥ is shown to be strongly frequency dependent in highly deionized liquid crystals.
Abstract: Measurements are reported of the frequency dependence of the conductivities σ⊥ and σ∥ in some nematic liquid crystals with strong positive dielectric anisotropy which are nematic at room temperature. The conductivity relaxation which causes σ∥ to increase already at frequencies <100 Hz in highly deionized liquid crystals are shown to be quantitatively in agreement with the dispersion of the orientation polarization of the molecules. The magnitude and sign of the conduction anisotropy σ∥−σ⊥ is shown to be strongly frequency dependent. The relaxation times τ⊥ and τ∥ due to the respective rotation of the molecules in a plane perpendicular and parallel to their long axes were determined.

43 citations


Patent
27 Jan 1975
TL;DR: In this article, a transformer is provided with a cover in the form of a heat pipe with an evaporator section extending from the cover into the dielectric fluid of the transformer.
Abstract: An electrical apparatus, such as a distribution transformer, having heat pipe cooling. The transformer is provided with a cover in the form of a heat pipe with an evaporator section extending from the cover into the dielectric fluid of the transformer. The top of the cover forms the condenser section of the heat pipe.

22 citations


Journal ArticleDOI
TL;DR: In this paper, a corrected curve of free ion yield versus electric field was given for n−hexane as well as new curves for 2−methylpentane, 2,2,4−trimethylpentane and carbon tetrachloride.
Abstract: A corrected curve of free ion yield versus electric field is given for n‐hexane as well as new curves for 2‐methylpentane, 2,2,4‐trimethylpentane, and carbon tetrachloride. Comparison with the Onsager theory of geminate ion recombination does not give reasonable agreement over the entire range of field strengths for any of the functions used.(AIP)

19 citations


Patent
30 Dec 1975
TL;DR: In this paper, the authors describe an electrical insulation system that includes a new and improved monolithic, polymeric, porous, open cell, fully impregnable, dielectric solid and an impregnating substance that may be applied to the dielectrics solid either at the factory prior to shipment or in the field prior to or during installation.
Abstract: An electrical insulation system includes a new and improved monolithic, polymeric, porous, open cell, fully impregnable, dielectric solid and an impregnating substance that may be applied to the dielectric solid either at the factory prior to shipment or in the field prior to or during installation. The dielectric solid is preformed to enable the quick and easy field installation of the insulation system in electrical apparatus. In addition, the porous, open cell nature of the dielectric solid in which very small communicating open cells are substantially evenly distributed throughout substantially all of the dielectric solid enables a dielectric fluid, such as a dielectric oil, to pass through the dielectric solid and thereby impart the self-healing characteristic of impregnated layered paper insulation to the new and improved insulation system. In a fluid dielectric system, the impregnating substance may be a dielectric oil or other dielectric liquid. In a solid dielectric system, the impregnating substance is used to fill the open cells or voids throughout the dielectric solid and may be an initially low viscosity dielectric liquid that is inserted into the dielectric solid along with an immobilizing agent and subsequently transformed by chemical reaction into a dielectric gel immobilized within the dielectric solid. The dielectric solid may be formed in accordance with either a sintering process or with a filamentizing process.

15 citations


Patent
15 Jan 1975
TL;DR: In this paper, a distribution transformer has inner and outer lowvoltage winding sections and a high-voltage wound section disposed there between, and the insulation structures separate the various winding sections.
Abstract: Distribution transformer having inner and outer low-voltage winding sections and a high-voltage winding section disposed therebetween. Insulation structures separate the various winding sections and include a relatively small thickness of solid insulating material and a liquid dielectric duct. Some of the solid insulating material is axially extended to increase the creep resistance of the winding. The insulation structures are also void of any metallic electrostatic shield or any other member which would hamper adequate processing of the insulation structure during the construction of the transformer.

13 citations


Patent
26 Jun 1975
TL;DR: An electrical capacitor is formed by winding alternating layers of single-sided metallized nonheat shrinkable dielectric material and of a heat-shrinkable Dielectric materials together as discussed by the authors.
Abstract: An electrical capacitor is formed by winding alternating layers of single-sided metallized nonheat-shrinkable dielectric material and of a heat-shrinkable dielectric material together. Radial leads are secured to the ends of the capacitor after it is wound by heating the leads and forcing them into the ends of the dielectric materials. The heat-shrinkable layers effectively seal off the electrodes from each other. In addition, the heat-shrinkable dielectric layers may provide higher current capacities, improved dissipation factor, better control over the temperature vs. capacitance characteristic of the capacitor, improved corona threshold voltage and improved control over the final value of the wound capacitor.

11 citations


Patent
03 Nov 1975
TL;DR: Spark erosion is applied to a nonconducting workpiece while employing a dielectric liquid comprising an emulsion of an aqueous solution of an electrolyte in an organic liquid and a surfactant.
Abstract: Spark erosion is applied to a non-conducting workpiece while employing a dielectric liquid comprising an emulsion of an aqueous solution of an electrolyte in an organic liquid and a surfactant.

10 citations


Patent
27 Oct 1975
TL;DR: In this paper, an electrical treater for resolving an emulsion in a vessel with an electric field created by an electrode receiving current from an external power source via a feed-through insulator, an electrical conductor and a high voltage bushing within a sidewall of the vessel.
Abstract: A B S T R A C T Electric treater system for resolving an emulsion in a vessel with an electric field created by an ener-gized electrode receiving current from an external power source via a feed-through insulator, an electrical conductor and a high voltage bushing within a sidewall of the vessel. A pressure conduit extends between the entrance bushing and the feed-through insulator, and it contains the electrical conductor within a dielectric liquid. A heat sink on the entrance bushing maintains its plastic insulation parts at substantially the tem-perature of the emulsion. System means maintain the dielectric liquid within the pressure conduit at sub-stantially the fluid pressure of the emulsion. Also, a heat exchanger on the pressure conduit maintains the feed-through insulator at substantially the same temp-erature at its pressure conduit and power source term-inals. As a result, the entrance bushing can operate at elevated emulsion temperatures (500°F) but at insig-nificant pressure differential whereas the feed-through insulator can operate at the ambient temperatures (80°F) of the power source but at substantially the fluid pressure of the emulsion (500 psi). Neither the bushing nor feed-through insulator must withstand simultaneously high pressure (500 psi) and high temperature (500°F) conditions. The present electrical treater system oper-ates at elevated temperatures and pressures with the relative safety of low pressure, low temperature conditions.

Patent
Gary Allen Vincent1
03 Mar 1975
TL;DR: Improved electrical devices such as transformers and capacitors containing an improved dielectric fluid consisting essentially of a major amount of a liquid polyorganosiloxane and a minor amount of cumene, methyl cinnamate or carbon disulfide are disclosed.
Abstract: Improved electrical devices such as transformers, and capacitors containing an improved dielectric fluid consisting essentially of a major amount of a liquid polyorganosiloxane and a minor amount of cumene, methyl cinnamate or carbon disulfide are disclosed.

Patent
03 Mar 1975
TL;DR: Improved electrical devices such as transformers and capacitors containing an improved dielectric fluid consisting essentially of a major amount of a liquid polyorganosiloxane and a minor amount of certain selected chlorendates which are soluble in said siloxane are disclosed as mentioned in this paper.
Abstract: Improved electrical devices such as transformers, and capacitors containing an improved dielectric fluid consisting essentially of a major amount of a liquid polyorganosiloxane and a minor amount of certain selected chlorendates which are soluble in said siloxane are disclosed.

Journal ArticleDOI
TL;DR: In this paper, a method for the design of a high-voltage solid insulation system used in airborne or satellite highvoltage components and systems is presented, and illustrated with a successful system now used in these applications.
Abstract: A method for the design of a high-voltage solid insulation system used in airborne or satellite high-voltage components and systems is presented, and illustrated with a successful system now used in these applications. The design is based on the elimination of corona in the solid, and principally involves making an insulation with a very high corona inception voltage and then controlling the electric field stress below that level. Examples of actual components and systems designed in this way are shown.


Patent
John Lapp1, Fred S. Sadler1
20 Jan 1975
TL;DR: An electrical capacitor having an improved dielectric system is described in this article, where the capacitor includes alternate layers of metal foil and polymeric dielectrics film which are impregnated with a liquid die-lectric composition composed of a mixture of mono-halogenated diphenyl oxide and a mono-helogenated alkyl diphosphoric acid diphensyl oxide, where the acid group contains from 1 to 20 carbon atoms in the molecule.
Abstract: An electrical capacitor having an improved dielectric system The capacitor includes alternate layers of metal foil and polymeric dielectric film which is impregnated with a liquid dielectric composition composed of a mixture of mono-halogenated diphenyl oxide and a mono-halogenated alkyl diphenyl oxide where the alkyl group contains from 1 to 20 carbon atoms in the molecule In processing the capacitor, the capacitor casing is vacuum dried at room temperature and the dielectric liquid is separately agitated under vacuum to remove gas from the liquid The degassified liquid is introduced into the casing and the liquid is subjected to a vacuum while maintaining the capacitor at room temperature to impregnate the polymeric layers with the liquid The capacitor has improved corona characteristics and low dielectric losses, and the liquid dielectric composition is substantially biodegradable

Journal ArticleDOI
TL;DR: In this article, the electric force plays an important role in the trapping of air bubbles under the capillary electrode dipped in a dielectric liquid, and the maximum trapping time is about 20 min.
Abstract: Trapping of air bubbles under the capillary electrode dipped in a dielectric liquid is found experimentally. The trapping is observed only in some kind of liquid in which a remarkable rise of the free surface along the electrode has been observed. Only bubbles injected from the charged capillary electrode can be trapped. The maximum trapping time is about 20 min. The electric force is shown to play an important role in the trapping. Trapped air bubbles slightly oscillate vertically and horizontally accompanied by a pulsation at a frequency of several kHz.

Patent
Gary Allen Vincent1
03 Mar 1975
TL;DR: Improved electrical devices such as transformers and capacitors containing an improved dielectric fluid consisting essentially of a major amount of a liquid polyorganosiloxane and a minor amount of certain selected ketones which are soluble in said siloxane are disclosed.
Abstract: Improved electrical devices such as transformers, and capacitors containing an improved dielectric fluid consisting essentially of a major amount of a liquid polyorganosiloxane and a minor amount of certain selected ketones which are soluble in said siloxane are disclosed.

Journal ArticleDOI
S. Tan1, K. Ahn, N. Ainslie, A. Mayadas
TL;DR: In this article, the breakdown voltage spectra of thin film dielectrics were measured as a function of time and temperature during application of linearly increasing (ramp) voltages.
Abstract: Using fast response detecting and recording equipment the breakdown voltage spectra of thin film dielectrics (with a GdCoMo first electrode and permalloy counter-electrode) were measured as a function of time and temperature during application of linearly increasing (ramp) voltages. For 1000 A thick SiO 2 films the dielectric breakdown events occurring at high voltages were seen to be strictly voltage-dependent, whereas those breakdowns occurring at low voltages exhibited a definite time-dependence in addition to a voltage-dependence. In this low voltage region slowly increasing voltages (low ramp rates) resulted in significantly greater numbers of cumulative failures, for a given attained voltage, than did rapidly increasing voltages. This time-dependence, transformed through a simple kinetic power law to a constant applied voltage experiment was found to be consistent with Peek's law of dielectric breakdown. The data and analysis suggest that reliable device operation will not be achieved if electric fields in excess of 0.6 × 106V/cm are applied across the dielectric.

Journal ArticleDOI
01 Feb 1975
TL;DR: In this paper, a simple alternative method is proposed which gives an analytical solution for the particular case when the spacecharge density is small, applied to a cylindrical wire located centrally between two parallel plates with a transverse liquid flow.
Abstract: The exact calculation of a charge trajectory in a streaming dielectric liquid requires the solution of the coupled Maxwell and Navier-Stokes equations, which can be solved using lengthy iterative numerical techniques. A simple alternative method is proposed which gives an analytical solution for the particular case when the spacecharge density is small. The technique is applied to a cylindrical wire located centrally between two parallel plates with a transverse liquid flow. Electrical and hydrodynamic stream functions are derived separately and are combined to give the charge trajectories for several values of the electric and flow parameters. The results are considered for the application to high-voltage streaming generators.

Journal ArticleDOI
TL;DR: The use of Fr-14 (CF 4 ) and Fr-116 (C 2 F 6 ) to increase the margin arc-over voltage in dry Mylar energy storage capacitors is investigated in this article.
Abstract: The use of Fr-14 (CF 4 ) and Fr-116 (C 2 F 6 ) to increase the margin arc-over voltage in dry Mylar energy storage capacitors is investigated. It is found that pressurization of capacitors with Fr-14 results in a small increase in arc-over voltage. However, pressurization with Fr-116 results in arcover voltages 1.5 to 2.5 times larger than obtained in air.

Book
01 Jan 1975
TL;DR: In this article, the effect of impurity particles in dielectric liquids was investigated and the effects of impurities on low-field conduction of liquid dielectrics were investigated.
Abstract: Mobility and Conduction.- Electron transport in high mobility liquid hydrocarbons and tetramethylsilane.- A maximum bound for electronic mobilities in liquid hydrocarbons.- Electron drift mobility measurements in liquid 3-methylpentane and the effect of impurities.- Hole conductivity in liquid hydrocarbons.- Carrier mobility in liquid crystals.- Electrical conduction in nematic liquid crystals.- High-Field Conduction.- Conduction adjacent to oil-immersed dielectric surfaces in a non-uniform field.- The effect of solid polymeric materials on the ionic conductivity of liquids under high electric stress.- Light emission studies in the interpretation of high-field conduction of dielectric liquids.- Frequency dependence of stress-induced cavitation in fluorocarbon liquids.- High-field conduction pulses in n-hexane.- High-Field Conduction.- Electrical conductance and breakdown in liquid hydrocarbons.- On the theory of filamentary single injection and high-field electric conduction and breakdown in dielectric liquids.- Transient electric field and space charge behaviour for drift dominated bipolar conduction in dielectric liquids.- Conduction-Impurities.- Simulation of charge transport following unipolar injection.- The effect of trapping and detrapping of electrons on the negative charge carrier mobility in liquid tetramethylsilane.- A contribution to the study of low-field conduction by impurity particles in dielectric liquids.- Influence of solid impurities on the electric strength of transformer oil.- High-field conduction in heavily contaminated transformer oil.- Effect of added electronegative substances (SF6, I2) on ion mobility in mineral oil.- Injection.- Monitoring of injection processes in dielectric liquids.- Charge injection in dielectric liquids by photoelectric emission.- Factors Controlling ion injection by metallic electrodes in dielectric liquids.- Conduction in insulating liquids due to carrier injection: nature of carriers injected and regeneration thereof by ionic polymers.- Photo-injection into n-hexane.- Free ion yields of some dielectric liquids and study of binary mixtures of those dielectrics irradiated by 60Co and 137Cs y rays.- EHD.- Electrohydronynamic stability of liquids subjected to unipolar injection.- Double injection with recombination: EHD stability and charge transfer.- The influence of induced motion of unipolar charge transport.- The electroviscous effect and its explanation.- Electrolytic conduction and EHD turbulence.- On the role of ions and dipoles on electroconvective processes in insulating liquids.- Field distributions in chlorobiphenyls under direct voltages.- Pre-Breakdown.- Study of a three electrode cell for the recording of the transient pre-breakdown phenomena in liquid dielectrics.- Corona and the molecular structure of insulating liquids.- Behaviour of a water drop in the pre-breakdown processes in insulating oil.- The effect of SF6 on partial discharge in transformer oil under non-uniform field.- Breakdown.- Breakdown time lag and time of flight and measurement in liquid dielectrics.- Investigation of time-lag characteristics-for a triggered spark gap in a liquid dielectric.- Cathode fall like discharge in dielectric liquids.- Memory effect in dielectric liquids being subjected to recurring discharges.- The assignment of appropriate dielectric stresses in liquids.- Mechanisms in Breakdown.- On the mechanisms of dielectric breakdown in liquids.- Breakdown of oil using one bare and one electrode coated with an insulating film.- Estimation problems in the step-function breakdown test.- Breakdown and infra-breakdown phenomena at low rates of stress application.- Cryogenic Liquids.- Ionic mobility measurement in dielectric liquids by the method of the full space charge limitation.- Corona light and corona pulse nitrogen.- The observation of dielectric breakdown in liquid nitrogen using discharge figures.- Some aspects of breakdown in liquid nitrogen.- Statistical analysis of the dielectric breakdown in liquid nitrogen under uniform field conditions.- Dielectric breakdown of flowing liquid nitrogen under D.C. and A.C. voltage.- Miscelaneous.- Chemical relaxation of the nonlinear dielectric effect in dipole equilibria.- Power factor of silicone liquids.- Electro-disintegration of dielectric liquids.- The faraday-sumoto effect.- Pulse generators with liquid dielectric gaps.

Patent
21 Aug 1975
TL;DR: A spark gap switch has a central electrode positioned within an annular electrode in a dielectric liquid or saturated vapor flow line, with coaxial or parallel plate electrical connections to said electrodes.
Abstract: A spark gap switch having a central electrode positioned within an annular electrode in a dielectric liquid or saturated vapor flow line, with coaxial or parallel plate electrical connections to said electrodes

Journal ArticleDOI
TL;DR: In this article, short models of the dielectric for a lapped polyethylene insulated superconducting cable are described and the impulse breakdown strengths and 50 Hz discharge inception fields are reported.

Proceedings ArticleDOI
01 Nov 1975
TL;DR: In this paper, a program of measurement of dielectric strength and partial discharge inception levels of polymeric insulating tapes at cryogenic temperatures was conducted to evaluate various materials in terms of their mechanical and electrical characteristics.
Abstract: The dielectric for a flexible superconducting power transmission cable will necessarily be in the form of multi-layered tapes, impregnated by supercritical helium, wound with butt gaps to provide flexibility.1 Major consideration for the choice of an appropriate dielectric are that the dielectric should posses suitable mechanical properties at low temperatures (5–10°K), the material should have very low dielectric loss (< 20 μ radian) and it should possess high enough dielectric strength. Economic considerations dictate that the cable should operate at very high electric stress levels. For example, the Brookhaven National Laboratory superconducting cable design2 specifies an operating stress 10 MV/m, free of any significant partial discharge up to a stress of 20 MV/m. So far no dielectric material simultaneously satisfying all the mechanical and electrical requirements cited above has been found and the search for a suitable dielectric tape is still in progress. In order to arrive at an appropriate material it is necessary to evaluate various materials in terms of their mechanical and electrical characteristics. It is in this connection that we undertook a program of measurement of dielectric strength and partial discharge inception levels of polymeric insulating tapes at cryogenic temperatures.


Proceedings ArticleDOI
01 Nov 1975
TL;DR: The Hughes Phoenix radar transmitter uses a liquid dielectric as a coolant as mentioned in this paper, and the amount of ionizable contaminant is measured by monitoring the volume resistivity of the coolant.
Abstract: The Hughes Phoenix radar transmitter uses a liquid dielectric as a coolant. In order to withstand the high temperatures in the transmitter, a silicate ester (the ester of silica acid and 2-ethyl butanol) has been chosen. One of the disadvantages of this liquid is the degradation products caused by contaminants such as water, organic acids, and inorganic salts. Since the radar systems may be repaired aboard an aircraft carrier, contamination of the liquid dielectric coolant is likely and it is important to monitor the concentrations of these contaminants. This is particularly true for the high voltage radar transmitter. The amount of ionizable contaminant is measured by monitoring the volume resistivity of the coolant. The water content of the coolant is measured by an electronic water sensor.



Journal ArticleDOI
TL;DR: In this paper, the authors investigated the electrical forces acting on a dielectric liquid in an electric field in the presence of a temperature gradient and showed that nonuniformity in the electrical conductivity of the medium can give rise to a hydrodynamic flow.
Abstract: The nature of the forces acting on a dielectric liquid in an electric field in the presence of a temperature gradient is investigated. It is shown that the electrical forces produced by nonuniformity in the electrical conductivity of the medium can give rise to a hydrodynamic flow.