Showing papers on "Insulator (electricity) published in 1970"

AC Flashover Tests at Project UHV on Ice-Coated Insulators

Abstract: This paper presents results of experimental studies on the flashover strength of ice-coated insulators. Two types of flashover have been found on ice-covered insulators. One is caused by hard and dry ice formed in temperatures lower than 15 °F. Another is caused by mixed conditions of ice and misty rain in relatively high temperatures of 20 to 30 °F. The flashover voltages of 25 units of 53/4- by 10-inch insulators were 288 kV (phase to ground) in the former condition and 246 kV in the latter. These results were obtained for uncontaminated insulators. Nonuniform voltage distribution along the insulator string produces these low flashover voltages. These tests were conducted at General Electric's Project UHV in the winter season of 1968-1969.

Insulators with Contaminated Surfaces, Part II: Modeling of Discharge Mechanisms

Abstract: This paper considers electrical discharge mechanisms as they occur across relatively dry zones on wet contaminated insulator surfaces. A mathematical model was assumed with constant surface resistivity, and constants were evaluated from experimental results obtained using a simple cylindrical geometry with a dry zone, wet contaminant, and electric stress much like those on suspension insulators.

Application of dimensional analysis to flashover characteristics of polluted insulators

Abstract: In the paper, the method of dimensional analysis is applied to determine the flashover characteristics of polluted insulators. Expressions deduced for the flashover voltage in a d.c. circuit under simplified conditions are found to agree with the analytical findings of previous authors. The work is then extended to flashover characteristics in a.c. systems, where the dynamic properties of arcs are introduced. It is found that the same functional dependence of the flashover voltage on pollution and insulator characteristics prevails as for d.c. conditions, although the magnitude of the flashover voltage may be different in the two cases. Finally, an expression for the velocity of arc propagation along the polluted insulator surface is deduced with due consideration of insulator, layer and circuit parameters. Of special interest is the dependence of the ultimate arc velocity on the short-circuit current of the test circuit, as well as the expression for the minimum voltage necessary to start arc motion. Whenever possible, the analyses included in the paper are compared with previous field and/or laboratory experience.

Electric water heater

Abstract: In accordance with this invention there is provided an electric water heater and storage tank wherein only a single electric heating element is vertically mounted near the bottom of the tank and is surrounded by a spaced-apart tube which is a good thermal insulator, such as a plastic tube. The insulator tube is open at the bottom for cold water inlet and has openings at the top for hot water outlet near the middle of the tank, forming a circulating system within the tank to cause cooler water to sweep across the surface of the electric heating element for economy and to greatly reduce stratification of the hot water within the tank.

Direct evidence of metal electrode diffusion into the dielectric of AlSiOAl capacitors in high electric field

Abstract: By electron diffraction the crystallization of the insulator in AlSiOAl capacitors with applied electric fields was studied. The analysis of the crystalline structures shows that electrode metal diffuses into the dielectric, and that this diffusion is connected with the crystallization.

Unbalanced Tensions in Transmission Lines

Abstract: A nonlinear analysis of an electric transmission line is presented for conditions involving imbalance in conductor tensions. The analysis is applicable to lines containing structures of arbitrary geometry and stiffnesses. Structure and insulator displacements are considered. Stiffness properties of structures, conductors, and insulators are derived. Equilibrium equations to be used in the analysis are formed. Two numerical methods of analysis, an iteration method, and a step-by-step linear increment technique are applied to the equilibrium equations. Both methods which have been programmed on a digital computer are applied to an actual transmission line containing flexible tubular steel structures. The iteration method has been found to be superior to the step-by-step method for the example analyzed. Analysis of this line has also shown that neglecting deflections of flexible structures with suspension insulators introduces substantial error.

Flashover Tests at Project UHV on Salt-Contaminated Insulators, Part II

Abstract: Results of experimental studies on the contamination flashover strength of EHV insulator strings are presented. The results compare favorably with a theoretical analysis by Boehne and Weiner in 1966-1967. Nonlinearity of insulation strength with insulator length has been investigated, employing a steam fog method to simulate natural humidity and fog. The nonlinearity is caused by nonuniform voltage distribution along contaminated insulator strings. Such nonuniform distribution is created by the capacitance of insulator units to ground. This relationship was clearly demonstrated by several indirect methods. The results should be very important in future contamination studies.

Insulator for electric wires

Abstract: An insulator for insulating wires, said insulator being tubular in shape with a longitudinal opening therein for receiving one or more wires, said insulator adapted to cover and insulate the wire or wires and/or the ends thereof, said insulator being deformable under pressure and having pressure sensitive adhesive material on the inside surface so that said insulator adheres to said wire or wires and to itself upon sufficient deformation.

Boundary-Relaxation Analysis of Rotationally Symmetric Electric Field Problems

Abstract: A new numerical method is described for the solution of electric field problems where the field is not bounded in space, but extends infinitely far. This method belongs to the class of boundary-relaxation techniques in which an artificial finite boundary condition is initially introduced to allow solution and then iteratively removed as the solution proceeds. The method has been implemented in extensive computer programs, which produce equipotential plots of the electric field in the neighborhood of dielectric and conductive bodies possessing rotational symmetry. Application to the analysis of suspension insulators and related devices is described, and several field plots exhibited for standard insulator types. The method permits sufficiently short computation times to allow detailed investigation of the effects of insulator contamination by conductive substances, variation of dielectric constant, or other factors.

Switching-Surge Flashover of EHV-UHV Towers

Abstract: Design curves are presented for switching-surge flashover of tower window gaps 20 to 39 feet (6.1 to 11.9 meters), bundle conductor-to-ground gaps spaced 20 to 50 feet (6.1 to 15.2 meters), and bundle conductor-to-tower leg gaps spaced 14 to 29 feet (4.3 to 8.8 meters). The critical flashover voltage range is from 1100 to 2700 kV. Together with the above, the following variables were investigated: time to crest, insulator string length, rain, window-shape, tower width, conductor entrance angle, and conductor configuration. In addition, work was accomplished on standard deviation, time to flashover, and flashover patterns.

Insulators with Contaminated Surfaces, Part III: Modeling of Dry Zone Formation

Abstract: A flat plate insulator with concentric electrodes and a fog guard is used to obtain the same qualitative behavior in leakage current and dry zone formation as a suspension insulator in a fog with horizontal wind for comparable levels of contamination and electric stress, thus demonstrating the importance of nonuniform wetting in this case. Attempts at mathematical description of the processes met with only qualitative success.

Method of fabricating buried metallic film devices

Abstract: Electrical conductors and field plates utilized in monolithic integrated circuit components are buried in insulating media by forming a high temperature resistant insulating film on the semiconductor substrate, depositing a metallic film thereover which is non-reactive with the insulator at temperatures of the order of 700* C or higher, and covering the conductive film with another high temperature resistant, non-reactive insulating film. After all fabrication steps for the integrated circuit device are completed, (which steps may optimally include diffusion into the semiconductor subsequent to deposition and encapsulation of the metallic film) contact to the metallic layer is made by etching a hole through the last deposited insulating film at one point with an etchant which is non-reactive with the metallic film, and metallizing the device in that region, making contact with the buried conductor. Such buried conductors may be utilized as conductors in printed circuit and monolithic semiconductor devices, capacitor plates, non-contacting cross-overs, and as gate electrodes in field-effect transistors, for example.

Ionization, Attachment and Breakdown in SF 6

Abstract: SULPHUR hexafluoride is widely used as an insulator in many electrical devices, but little is known of its fundamental electrical properties, particularly at voltages above about 100 kV. As the first part of an investigation on the growth of pre-breakdown ionization in SF6, we have carried out measurements from which values of the apparent primary ionization coefficient α′ have been determined, at pressures in the range from 50 to 400 torr and for voltages up to about 200 kV. We report here a dependence of the coefficient α′ on gas pressure, not previously observed in SF6, which is significant to the insulating properties of the gas and which can be related to the fundamental collision processes occurring.

Test Line Experience with HVDC Overhead Transmission

Abstract: Tests were conducted on a high-voltage overhead direct-current test line. Values of radio interference and corona loss were established for certain conductor configurations and pole spacings. Relations between radio interference and corona loss and some weather variables were evaluated. Insulator leakage currents and induced overhead ground wire currents were investigated.

Flashover Test at Project UHV on Salt-Contaminated Insulators

Abstract: The results of experimental studies on the contamination flashover strength of different shapes of transmission line insulators are presented Insulators with mechanical strengths from 15 000 to 90 000 pounds and with disk diameters from 10 to 152/4 inches were used on these tests New types of fog insulators with high creepage distance showed better performance than the others Tests on long insulator strings also have been conducted for standard-type disk insulators Nonlinearity of insulation strength with insulator length was indicated at voltage levels of 350 kV and above, ie, 600-kV phase-to-phase voltage These tests employed the steam- fog method used at General Electric's Project UHV since May 1968

Improvements in or relating to vacuum interrupters

Abstract: 1,206,297. Vacuum switches; fluid actuation of switches. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 4 Dec., 1968 [4 Dec., 1967], No. 55104/67. Heading H1N. Vacuum switches designed to be coupled together in series for high voltage use are made sufficiently strongly to support the stresses imposed without the need for any additional supporting structure. The envelope of the switch comprises a single tubular insulator 1 of porcelain or glass ceramic to which are cemented two metal rings 18, 108. The rings are secured to respective adapter castings 2, 102 which link together adjacent switches. The two ends of the insulator are sealed by metal plates 9 and bellows 11 which allow movement of contacts 24, 34 relative to contacts 4, 14 fixed inside the insulator. The switches are operated by pistons 22 supplied from a high pressure gas reservoir by a valve controlled by a linkage (Figs. 4, 5, not shown) as described in Specification 1,206,298. Impedances 57 divided the voltage equally between the switches and are located with feed pipes 55 in porcelain housings 56.

Inductive electric apparatus

Abstract: An inductive electric apparatus which comprises a polycylic hydrocarbon oil mixture having a flash point of more than 150 DEG C and consisting of polycyclic naphtenic hydrocarbons having two to five rings and polycyclic aromatic hydrocarbons having two to four rings, each side chain alkyl group attached to said rings having not more than four carbon atoms, an electroconductive coil and a cellulose insulator in combination. The inductive electric apparatus can have a larger increase in allowable temperature than that of a combination of the ordinary hydrocarbon insulating oil and the cellulose insulator, and accordingly it is possible to make the apparatus smaller and lighter.

The Effects of Insulator Surface-Ion Migration on MOS and Bipolar Integrated Circuits

Abstract: The effects of mobile ions at insulator surfaces on integrated circuits are reviewed. The published literature is reviewed and recent experimental results are presented. Recent data are given on inversion voltages and surface recombination velocities both in regions under aluminum metal and in regions not covered by metal. Other data include measurements of surface conductivity on different types of surfaces, and a demonstration of the existence of mobile ions at an interface between two insulator layers. Techniques are described for minimizing surface-ion effects on integrated circuits.

Thermionic gas-pressure-bonded sheathed insulators and method of producing same

Abstract: The collector of a thermionic converter, an insulator, and a metal sheath for the insulator are directly gas-pressure-bonded together such that the trilayer thus formed is stress relieved and maintains good structural integrity during machining and during thermocycling caused by operation of the converter. The insulator is alumina and the collector and sheath consist either of niobium metal or Nb-1 wt percent Zr alloy.

Vacuum switch with power fuse

Abstract: A vacuum switch used for switching high voltage capacitive loads comprises a support chassis on which a hollow support insulator is mounted. One or more vacuum interrupters, each comprising an insulated envelope and relatively movable contacts, are mounted on the hollow support insulator. Operating means are mounted on the support chassis and comprises an insulated operating rod which extends through the hollow support insulator for operating the vacuum interrupter(s). A replaceable power fuse is provided. Means, including a stand-off insulator and fuse connectors are provided to mount the switch in parallel physical relationship with the hollow support insulator and to electrically connect the fuse in series circuit with the vacuum interrupter(s). In one embodiment, a single vacuum interrupter is provided and it is disposed in parallel physical relationship with the hollow support insulator. In other embodiments, a plurality of vacuum interrupters are provided which are transversely disposed with respect to the hollow support insulator. In one of the other embodiments, one of the vacuum interrupters is physically located within the stand-off insulator.

Integral electrical insulator and supporting member for electrical wire fence

Abstract: An integral insulator assembly is provided for supporting electrically charged wires on a fence, comprising an insulator body molded of a moldable material such as a synthetic plastic, and having a metallic means affixed therein for mounting the insulator on a fence post.

Methods of manufacturing electrical insulating structures

Abstract: Methods of manufacturing insulating structures for electrical inductive apparatus, such as angular, channel-shaped structures for coil edge insulation. The methods include the step of subjecting the insulator blank to steam for a predetermined period of time, which step is promptly followed by forming the blank into the desired configuration in a heated press.

Coaxial electric arc discharge devices

Abstract: Triggerable electric arc discharge device includes coaxial cathode and anode electrodes defining therebetween a hollow cylindrical primary arcing gap. A trigger assembly having an elongated longitudinal configuration is inserted into a longitudinal bore formed in and adjacent to the surface of the cathode electrode so as to be partially exposed into the interelectrode gap. Trigger assembly includes a ceramic hollow cylinder surrounding a metallic trigger electrode. Trigger gap is defined by extension of the trigger electrode past the inboard end of the trigger ceramic insulator and a trigger gap exists between the extended portion of the trigger electrode over the inboard end of the ceramic insulator and to the body of the cathode electrode. A voltage is connected between anode and cathode electrodes and a relatively low voltage pulse is supplied to the trigger electrode, causing breakdown of the trigger gap. Trigger arc formed thereby causes propulsion of ionized specie into the main gap and breakdown thereof.

Metal-insulator-metal solid-state rectifier

Abstract: A metal-insulator-metal layered structure is disclosed which is useful as a rectifier of AC voltage. One of the metal layers is advantageously in the form of a crossgrid-type geometry, in order to afford a large perimeter of contact with the insulator layer. Electrons are injected at the edges of the metal grid through the insulator when the grid goes electrically negative, but not when it goes positive; thereby, rectifying properties are afforded by this metal-insulator-metal structure.

Multiring hollow high-voltage insulator with external and internal sheds

Abstract: An insulator for supporting electrical switches, buses and the like in a high-power distribution system is constructed from annular shells or rings having both internal and external sheds with corrugations on the undersides thereof to increase creepage distances and to function as rain shields. The diameters of the rings are selected according to the stability required for the insulator, while the height of the individual assemblies are selected according to dielectric requirements.