Showing papers on "Insulator (electricity) published in 1982"

Surface flashover of solid dielectric in vacuum

Abstract: The surface of a solid dielectric insulator becomes electrically charged when subjected to a high‐voltage stress in vacuum. A method for calculating the surface flashover voltage based on the assumption that the discharge occurs in a layer of desorbed gases from the insulator surface is proposed. The electric field strength required to cause surface flashover is calculated by taking into account the secondary electron emission characteristics of the dielectric material. The dependence of the surface flashover field on the insulating material is deduced. A dependence of the flashover voltage on the insulator length to a power law of 0.5 is theoretically predicted. The calculated surface flashover voltage is compared with the previously reported measurements and good agreement is obtained.

Computation of Three-Dimensional Electric Field Problems by a Surface Charge Method and its Application to Optimum Insulator Design

Abstract: This paper describes an improved surface charge method for computation of three-dimensional electric field distribution and its application to optimum insulator design. In this method, each curved surface on which the charge is distributed is divided into many curved surface elements instead of planar elements. After computing numerically the charge distribution, the distributions of both potential and electric field are obtained. Because the use of many curved surface elements provides a good approximation of the insulator contour, the correction of insulator contour to achieve optimum insulator design can be performed smoothly.

Chemical vapor deposition and characterization of phosphorus nitride (P3N5) gate insulators for InP metal‐insulator‐semiconductor devices

Abstract: A new gate insulating film consisting of P3N5 was formed on an InP surface by a new chemical vapor deposition (CVD) technique. A suitable combination of reagents (PH3 and NH3) made P3N5 CVD feasible in an ambient free from oxygen and having excess phosphorus pressure. The new insulator revealed ohmic conduction with a resistivity as high as 104Ω cm. The breakdown field intensity increased up to 107V/cm at room temperature. The low frequency dielectric constant was 3.7 e0. A very minor hysteresis was seen in the capacitance‐voltage curves measured on P3N5‐ InP metal‐insulator‐semiconductor diode. The interface state density was reduced to 1012/cm2eV at an energy near the conduction band edge. Photoluminescence spectra were measured before and after CVD to determine the surface passivation effect.

Electrical breakdown of insulators by one‐carrier impact ionization

Abstract: Theories for current runaway by one‐carrier impact ionization are generalized for insulators, in which the injected and ionizing charge carrier type is subject to trapping. Relations are derived for the critical current runaway field Fr and time to breakdown tr , and written in simple forms, offering physical insight into breakdown processes. A trapped charge of injected carriers is frequently established in the insulator, before a current runaway process develops. The breakdown relations show that the effect of such a trapped charge can be a significant increase in Fr and tr , as observed in several inorganic and organic insulators. The trapped charge is not always established on fast ramp tests. In such cases an anomalous range is predicted and observed in the breakdown characteristics, in which the breakdown field diminishes with decreasing time to breakdown. Breakdown models developed here will be found in the companion paper to offer consistent interpretations for observations on aluminum oxide.

Magnetic inhibition of insulator flashover

Abstract: Electrical breakdown across a vacuum/plastic interface in the presence of applied or self‐generated magnetic fields, B?3.5 T, was investigated. The E×B drift of charged particles near the interface in these experiments was away from the insulator surface. The self‐magnetic field effects on a plastic vacuum insulator flashover were examined with inductive loads, particle beam loads, and imploding plasma loads. Average breakdown electric fields of up to 38 MV/m were observed. Power densities of 100 TW/m2 were passed through acrylic‐vacuum interfaces. The flashover electric fields were improved over the B = 0 fields from previous experiments by factors of 7.1, 5.0, and 1.8 for the −45°, 0°, and +45° insulators, respectively.

Flashover test of Artificially iced Insualtors

Abstract: Test apparatus and procedures were developed to test energized, non-contaminated, 120 kV system insulators under simulated freezing rain conditions. The flashover performances were compared between non-ceramic composite transmission line insulators and standard porcelain 53/4 x 10 inch suspension insulators. Standard and long leak Multicone porcelain insulators were also compared in the icing tests to standard porcelain station post insulators. Icing tests at several voltage stresses provided the full flashover-range of the insulators from the minimum or zero flashovers in ten trials up to the maximum or 10 flashovers in 10 trials. Using the desired insulator voltage stress flashover curve for specific insulator types and the voltage stress applied to the insulator, the comparative probability of flashover due to ice storms on the system can be evaluated for 120 kV, 230 kV and 345 kV systems.

Study of the double layer at an insulator/liquid interface by step voltage transients

Abstract: The electrical behaviour of dielectric liquids is strongly influenced by the double layer at solid/liquid interfaces. When the solid is a metal, the injection of ions depends on the structure of this layer. A new method is proposed which evidences the presence of such a layer at an insulator/liquid interface. A liquid containing a known amount of electrolyte is subjected to a voltage step, the electrodes being covered with polymer films. From the shape of the transient currents, the total charge displaced across the liquid gap is measured, and the corresponding zeta potential calculated. zeta depends mainly on electrolyte dissolved in the liquid for a given insulator/liquid pair and is much higher than the known values at a metal/liquid interface. A simple model considering the diffuse layer as a charged sheet may be applied. However, at voltages high enough, electrohydrodynamic motion of the liquid contributes to the convective transport of charge in a similar way to that already studied in the case of unipolar injection in insulating liquids.

Flashover Tests of Artificially Iced Insulators

Abstract: Test apparatus and procedures were developed to test energized, non-contaminated, 120 kV system insulators under simulated freezing rain conditions. The flashover performances were compared between non-ceramic composite transmission line insulators and standard porcelain 5 3/4 x 10 inch suspension insulators. Standard and long leak Multicone porcelain insulators were also compared in the icing tests to standard porcelain station post insulators. Icing tests at several voltage stresses provided the full flashover range of the insulators from the minimum or zero flashovers in ten trials up to the maximum or 10 flashovers in 10 trials. Using the desired insulator voltage stress flashover curve for specific insulator types and the voltage stress applied to the insulator, the comparative probability of flashover due to ice storms on the system can be evaluated for 120 kV, 230 kV and 345 kV systems.

Surface Topography of Printed Wiring Boards and Its Effect on Flashover

Abstract: Breakdown voltage values between conductor paths on epoxy-glass printed wiring boards (PWB's) are shown to lie on the Dakin curve relating the breakdown voltage with the dielectric constant and conductor separation on the insulator. However, the insulator surface roughness is shown to affect the breakdown voltage, the smoother the surface the lower the breakdown voltage. With a roughness (peak to valley) on the order of 10 µm or greater on epoxy-glass, the breakdown voltage approaches that of an equivalent air gap. Multiple filamentary discharges were observed per flash over similar to normal air breakdown. Erosion products from flashover include small copper spheres, from the damaged printed wiring lines, scattered around the damaged area on the PWB where, in many cases, the glass fiber supports were exposed. These effects can accelerate the degradation of the PWB insulator substrate.

Material Studies in a High Energy Spark Gap

Abstract: The chemical interactions and physical processes occurring in a high energy spark gap with different combinations of gases, electrodes, and insulators were studied. The electrodes studied were graphite and a tungsten-copper composite; the insulators were Lexan and Blue Nylon; and the gases were N2 and SF6. The gas composition was monitored with a mass spectrometer. Spectroscopic techniques were used to observe the arc channel. The electrode surfaces were studied with several surface analysis techniques, including scanning electron microscopy, electron spectroscopy for chemical analysis, Auger electron spectroscopy, and X-ray fluorescence. The breakdown voltage distribution was examined for different material combinations. The plasma chemistry processes involving the gas, electrode, and insulator materials were found to affect the voltage self-breakdown distribution. The detailed surface analysis gave information about the nature of the chemical processes. The presence of Blue Nylon seemed to have a more adverse effect than Lexan and graphite seemed to have a narrower voltage distribution than the tungsten-copper composite.

Gas Breakdown in Case of Steep-Fronted Pulses and Insulator Interfaces

Abstract: Two fundamental factors influencing the insulating characteristics of compressed gases are steep-fronted overvoltages and interfaces between gas and solid insulators. In order to estimate the influence of steep-fronted overvoltages it is necessary to know the limiting voltage-time-characteristics, that is the formative time lag. Especially in electronegative gases it is necessary to separate the statistical time lag from the formative time lag as the first time interval may be many orders of magnitude higher than the second. It will be shown that especially in SF6 the formative time lag may be either extremely short or rather long, mainly influenced by the field distribution. In compressed gas insulation the breakdown voltage is reduced by even ?clean? insulator surfaces. In this case breakdown is induced by one or several micro-discharges caused by local field enhancement at the insulator surface. Further electron multiplication must be caused by photoionization. Breakdown occurs if several micro-discharges develop and grow together.

An investigation of contact-charge accumulation on insulators repeatedly touched by metals

Abstract: When insulators are repeatedly touched on the same spot by a metal, it is found that the charge transferred to them increases on each contact This contact-charge accumulation has been noted by many authors and is surprising and unexplained The present authors report an experimental investigation of the charge accumulation on hard crystalline insulators They show that the charge accumulation can occur as the result of a small electrical conductivity in the insulator, and propose an explanation for the charge accumulation in these materials

Method for bonding insulator to insulator

Abstract: A method for making an airtight seal between a pair of insulator elements,uch as glass plates, without destroying any fine structure etched in the insulator elements. A thin metal film is deposited on one of the elements to be sealed and then placed in intimate contact with the other element to be sealed. The elements are then heated to a temperature well below their softening point, but high enough to significantly enhance the ion mobility in the insulator. A voltage is applied across the interface and the resulting anodic reaction consumes the film at the interface while producing a strong hermetic bond between the insulator elements.

Voltage breakdown between closely spaced electrodes over polymeric insulator surfaces in air

Abstract: Voltage breakdowns of some narrow gap electrodes [2–10 mil (0.05–0.25 mm)] on polymeric insulator surfaces (epoxy‐glass and triazine) have been examined over the pressure range from atmospheric pressure to 127 Torr and are shown to be an air breakdown modified by the presence of the insulator. Breakdown values as a function of the number of the breakdown and discharge energy level were also examined. In the worst case the breakdown voltage was observed to decrease by approximately 1300 V after about five successive breakdowns. The breakdown voltage between narrowly spaced metallic contacts on dielectric surfaces has been assumed to exhibit a Gaussian distribution. Non‐Gaussian, bimodal distributions have been observed in the present work. These bimodal distributions, found on fine line epoxy‐glass and triazine printed wiring boards, and attempts for explanation in terms of the flashover discharge initiating mechanisms, including the effects of ultraviolet radiation and a negative‐ion flux on breakdown, ar...

Coupling supporting insulator

Abstract: In the case of a supporting insulator (1), especially for high-voltage interruptor switches, having cavities (2, 3) for accommodating attachment means, in order to confirm whether high voltage is present on a busbar (22) which is carried by the supporting insulator (1) or on an interruptor switch (24), a capacitive voltage divider is arranged in the cavities (2, 3) in the insulator (1), an electronic circuit being connected to that part of the capacitive voltage divider which is free of high voltage, the output of which electronic circuit is connected to an associated switching element (13) in order to confirm and/or display the high voltage on a busbar (22) which is connected to the insulator (1), or in order to operate a high-voltage switch. The capacitive voltage divider is formed by two electrodes (4, 5) which are potted in the insulator (1) at a distance from one another, the electrodes (4, 5) preferably being constructed to form hemispheres (6, 7) at their ends, which hemispheres (6, 7) are opposite one another in the insulator (1), and that electrode (4) to which high voltage can be applied is connected to an attachment part (8) which can be connected to a busbar support. The electronic circuit is preferably arranged in a cartridge (9) which can be inserted into a cavity (11) in an attachment screw (10).

Charge Simulation Modeling of Practical Insulator Geometries

Abstract: A brief review of the charge simulation technique used for the calculation of high voltageelectrostatic fields, and its application to a typical transmission line disc insulator sectionunder pollution-free conditions, is presented. The use of ring and line charges has been found to be quite adequate for the modeling of the field distribution in and around the insulator with an accuracy in the representation of electrode potentials well within 1% of the maximum potential difference. The discrepancy in representing the inter-dielectric interface conditions is usually a maximum of about 9% but may be as large as 17% for the tangential electric field.

Method for determining the characteristic behavior of a metal-insulator-semiconductor device in a deep depletion mode

Abstract: First and second voltage sweeps are applied to a metal-insulator-semiconductor device with the device in a deep depletion mode during at least a portion of each sweep. Capacitance-voltage characteristics of the device are determined for at least a portion of each sweep while the device is in the deep depletion mode. Minority carrier generation parameters of the device in the deep depletion mode are determined based on the capacitance-voltage characteristics for the first and second voltage sweeps.

Rapid-heating, high-temperature-stable spark plug for internal combustion engines

Abstract: In order to obviate the necessity for design compromise of spark plugs with respect to their operating temperature, so that the ceramic insulator (18) of the spark plug will rapidly reach the temperature at which deposits thereon will inherently burn off (about 400° C.-450° C.) while not becoming so hot as to cause spurious glow ignition within the combustion chamber of an internal combustion (IC) engine, the end portion of the insulator is formed with a central opening (19/3) within which a metal core (24) is included which has a temperature coefficient of expansion such that, at temperatures below between 400° C.-450° C. it is spaced by a narrow gap (25) from the inner surface of the insulator (see FIG. 1) but, as the spark plug becomes hot, the gap 25 closes (FIG. 2), thereby providing good heat transmission from the insulator to the center electrode structure (21, 23, 24) and thereby maintaining the insulator at a temperature below that at which it might glow. Suitable materials for the center electrode are aluminum bronze, or other materials having a heat transmission characteristic of at least 90 W/mK. The insulator, preferably, has a higher-than-usual flux content so that, at low temperatures, its heat transmission characteristics are poor, to insure rapid heating to free combustion temperature of possible deposits.

High voltage insulator assemblage having specially-chosen series resistance

Abstract: The invention relates to an outdoor high voltage insulator, wherein the flashover due to the effect of external layers or deposits of pollution is prevented or at least shifted in the direction of higher degree of pollution. A resistance element (1) is connected in series with the insulator itself (2), with the leakage current prior to flashover producing a voltage drop over the resistance element (1). This voltage drop reduces the voltage on the insulator and prevents or retards flashover.

Mounting structure for electric elements

Abstract: Disclosed is a mounting structure for electric elements in circuit blocks of an electric circuit, particularly suitable for an ultrahigh-frequency circuit, allowing such elements to be automatically mounted as well as soldered, by such a way that holding parts with configurations and dimensions compatible with terminal parts of the elements are provided at portions of metal pieces as wiring conductors respectively, which are embedded in a frame made of an insulator at a proper distance, and the elements are mounted and secured so that the terminals thereof are positioned on the holding parts of the metal pieces.

Device for controlling tightness of vapour pipes

Abstract: 1. A surveillance provision for a medium-containing vessel - more especially for pipes carrying steam (2, 137) that shall detect leaks in the same, by means of the following : an electrical resistance wire (6, 107) for the monitoring of temperature, a humidity independant hygroscopic insulator (5, 105) and an electrical conducting wire (3, 102) for the monitoring of humidity, as well as an evaluation unit (20) for the detection of leaks comprising of a temperature measuring unit (21) and a humidity measuring unit (22), distinguished by the fact that the electrical resistance wire (6, 107) is disposed spirally around the electrical conducting wire (3, 102) in the longitudinal direction, being held at a constant distance from the same by the hygroscopic insulator (5, 105) ; the electrical resistance wire together with the electrical conducting wire (3, 102) and the hygroscopic insulator (5, 105) form a multifonctional temperature-humidity-measuring cable (1, 101, 111).

Temperature dependence of the electric field gradient in CdSe and HfO2

Abstract: The time differential perturbed angular correlation technique was applied to study the electric field gradient in the semiconductor CdSe and the insulator HfO2 at different temperatures. Whereas the semiconductor CdSe shows an increasing quadrupole coupling constant with increasing temperature, the insulator HfO2 exhibits no temperature dependence of the electric field gradient over the whole temperature range investigated.

Molded coil structure

Abstract: An economical and light-weight molded coil structure wherein sheet-form electrical insulator layers containing a thermosetting resin are wrapped around the inner and outer peripheries of a coil to function as a casting mold, and end-enclosing resin layers are applied to the both end faces respectively of the coil not covered with the sheet-form insulator layers. A gas is charged to be sealed in the coil.

A sensitive method for measuring surface conductivity of insulators

Abstract: A method is described for measuring the surface conductivity of insulating thin films. The conductivity is determined by observing the current transients while charging a capacitor whose dielectric is the insulating material and part of whose top electrode is the insulator surface. No elaborate sample preparation or experimental apparatus is required. Results are presented for oxide thermally grown on silicon, where sheet resistances between 1016 and 1020 Ω/⧠ were obtained for different values of relative humidity. The method can also be applied to a thin conducting layer on top of a thicker insulating film.

Detector for defective insulator

Abstract: PURPOSE:To detect the charge voltages of insulators safely with high accuracy in a detector for defective insulators having insulation characteristics cylindrical rollers moving on insulators by making a voltage divider freely movable and fixable to and at measuring positions. CONSTITUTION:A moving body 3 has two rows of roller groups 4, 4' arranged with plural pieces of insulation characteristic cylindrical rollers 20 consisting of electrical insulating materials in parallel to a plate shape, and moves by rotating on duplex insulators 1, 1'. A voltage divider 6 is mounted between the insulators 1 and 1' below an intermediate part 5. An optical voltage sensor 7 is connected to one end of the divider 6 and an expansion type insulation control rod 8 to the central upper part of the body 3 via a control rod connecting part 17. Contactors 12 that contact the insulator set at a right angle thereto are mounted rotatably to both ends of the voltage divider, thereby measuring partial voltages at the measurement point P of insulator fitting 2. The output of the voltage divider is fed to a measuring device via an optical voltage sensor 7 by means of an optical cable or the like and therefore the charge voltages of the insulators are measured with high accuracy without receiving faults such as electromagnetic induction.

Fabrication design and electrical evaluation of bulk-graded filled polymer post insulators

Abstract: An investigation has been made of the feasibility of grading an electric field by means of electrically active particulate fillers in polymeric matrix materials. Concepts investigated included linear resistive, nonlinear resistive and capacitive grading. This paper describes the design, fabrication and electrical evaluation of bulk-graded filled polymer insulators. The design emphasized in the study was a capacitively graded 23 kV post insulator.

Flat TV screen with cold cathode matrix - has bi-metal face column conductors with insulator separation from line conductors

Abstract: The flat TV tube comprises a front glass (1) a few mm thick which has the anode strips (4), with associated phosphors (6), on the inside surface The back plate (2), also glass, supports the metal-insulator-metal cold cathode matrix (9) in which the metal is titanium and the insulator titanium oxide The matrix comprises line conductors (8), then the insulator (9) followed by column conductors (11) which have round apertures (12) at the crossing point with the line conductors (8) The round apertures are between 02 and 03mm in diameter and are backed by a third metal (13) of 2 to 20nm thickness which forms the second metal plate of the cold cathode structure The two metals (8,13) comprising the cold cathode are titanium and the column conductors (11) may be either titanium, gold or platinum

SF6 gas insulating electric apparatus and process for producing the same

Abstract: A SF₆ gas insulating electric apparatus usable as a circuit breaker, etc., containing a SF₆ gas insulator and a resin insulator, both of which insulators are present in an atmos­ phere to be exposed to arcs, characterized by making at least the surface portion to be exposed to arcs of the resin insulator from a polymer containing nitrogen atoms or a polyolefin resin, and if necessary together with an inorganic filler powder, is excellent in both surface and inner arc resistance and can maintain breaking performance for a long period of time.

Thermo-magnetic recording method

Abstract: A method of thermo-magnetic recording employs a recording medium of a magnetization material disposed on an insulator. An area on the medium is joule-heated via the application of a voltage across contacting electrodes up to a bias point, and a heat pattern is applied in the form of an image to form a magnetic latent image.