Showing papers on "Insulator (electricity) published in 1981"

Review of high-voltage gas breakdown and insulators in compressed gas

Abstract: In the past ten years there have been significant advances in the theoretical and experimental analysis of high-voltage gas breakdown and surface flashover of insulators in compressed gases. This has probably been fostered by the recent growth in the design and application of gas-insulated high-voltage equipment. The review describes the characteristics of compressed-gas breakdown, including the effects of failure of Paschen's law; conditioning; electrode area; material and surface; breakdown-voltage distribution; particle contamination; voltage waveform; temperature; and gas mixtures. The insulator-flashover characteristics are then described, including the effects of insulator-electrode interface; insulator material; insulator shape; voltage waveform; charge generation; particle contamination; surface contamination; conditioning; flashover distribution; and dependence on type of gas. The various mechanisms proposed for gas breakdown and insulator flashover are reviewed and discussed in relation to the experimental characteristics. Future theoretical and experimental work is suggested to clarify the gas-breakdown and insulator-flashover mechanisms, and which would also help bring about the design of improved high-voltage gas-insulated systems.

Studies on Performance of Contaminated Insulators Energized with DC Voltage

Abstract: Several types of insulators with a variety of contaminants and test methods were tested using dc voltages. A thyristor controlled dc power source provided a sufficiently stiff source for dc contamination testing. The dc performance is influenced by the contamination degree both for soluble and insoluble materials, contamination uniformity, insulator shape and relationship of total leakage distance to insulator diameter. Generally, the performance with dc shows linearity with respect to string length, but the dc values are generally lower than with ac.

Breakdown and Wearout Phenomena in SiO2

Abstract: Technological improvements have largely cancelled the effects of contaminations but the mechanisms of shorting at high and medium fields have not been understood so well New experimental evidence is incompatible with existing breakdown theories Novel electrical testing techniques have given evidence that charge incorporation or charge flux through the dielectric plays an essential role in the deterioration of the insulator In the absence of a sound theory a model will be discussed assuming gaseous discharges

Electrical Reliability of DC Line Insulators

Abstract: Recent investigations have shown that the environment of dc lines is more damaging to insulation than that of comparable ac lines. Various mechanisms which can lead to failure of ceramic or composite insulators have been investigated. Results are reported for ceramic insulators on thermal breakdown and ionic migration. For composite insulators, we have studied ionic migration through the fiber glass rod and through the housing. The harmful effect of humidity in the fiberglass material is again evidenced. We also studied erosion due to dry band arcing. The erosion rate on the housing materials commonly used is three to five times larger than in a comparable ac test. This shows the importance of the design of the insulator on its reliability. In some cases, materials that do not track in ac, track under a dc stress.

DC Flashover Voltage Characteristics of Contaminated Insulatirs

Abstract: An investigation was made of the influence of the dc power source on the withstand voltage ofntam-contaminated insulators. A thyristor-controlled power source was found stiff enough for the tests. DC contamination tests on various insulators were also carried out. The dc withstand voltage is generally lower than the ac one (rms). There seems to be a tendency that the rate of decrease in dc withstand voltage becomes larger as the contamination degree increases. The dc withstand voltage depends more strongly than the ac one on the insulator shape. The leakage distance per unit withstand voltage increases with the diameter of the insulator. The dc withstand voltage was also affected by the kind and the amount of insoluble material used, as is the case with ac. The withstand voltage decreases with an increase in the deposit density of insoluble material even at the same ESDD. The dc withstand voltage of the insulators ilators with noniform contam-contamination was not less than that based on ESDD assuming uniform contamination. Shown finally is then-conceptual design of insulator assemblies for the ±600 kV dc class.

Minimum Test Requirements for Non-Ceramic Insulators

Abstract: This document* combines the experience and expertise of electric power utilities, manufacturers, and research laboratories into a single report that provides minimum test requirements for non-ceramic transmission insulators. The requirements are divided into material tests and insulator design tests that are needed to assess the relative merits of a variety of possible materials and insulator designs. The paper is intended for use by electric power utility engineers and insulator manufacturers to establish minimum material and design specifications for non-ceramic insulators. Insulators failing to meet the minimum test requirements should not be considered for long term use because of unsatisfactory materials, design, or both.

Wind Tunnel Studies of the Insulator Contamination Process

Abstract: This paper describes a small wind tunnel that was constructed to study the effects of wind, electric field, and insulator geometry on the insulator contamination process. The wind tunnel is operated with a kaolin clay and NaCl salt injection system. A voltage source is also available. Several insulator shapes, with voltage applied, were exposed in the wind tunnel. Preliminary test results indicate that wind tunnel contamination deposition is similar to that observed on naturally contaminated insulators. Sampling methods currently in use may not allow realistic comparison of flashover performance between uniform and nonuniform contamination. Other preliminary observations indicate that the effect of the electric field on contamination rate is greater than previously estimated. Estimation of site severity for insulator design, when using unenergized insulators, should be corrected for this effect.

Bushing for gas-insulated electrical equipment

Abstract: The invention comprises a bushing surrounding an electrical conductor, including a porcelain tube which employs a gaseous insulator, an insulating tube disposed with a space of small volume set relative to the inner periphery of the porcelain tube, the small space being filled with an insulating medium which is deformable with a predetermined force. According to the construction, when the porcelain tube has been damaged, its fragments can thus be prevented from scattering far. The flashover of the bushing can be prevented by disposing compression springs in the lower part of the insulating tube, and the electric field distribution of the outer surface of the bushing can be improved by coating the surface of the insulating tube with an electrically-conductive coating material.

D.C. gas discharge display panel with internal memory

Abstract: A D.C. gas discharge display panel for operation in a storage mode with internal memory, comprises a gas filled envelope bounded by a pair of glass plates (2 and 3), which carry on their respective internal surfaces orthogonal arrays of cathode conductors (4) and anode conductors (6) separated by a discharge gap (30). The array of cathode conductors is covered by a layer (10) of resistive material, which in turn is covered by a cermet layer (12). The cermet layer protects the cathode conductors from ion bombardment induced sputtering during discharge. The layers provide a resistance to each discharge cell, and provide isolation between individual cathodes by reducing discharge spreading along the cathode conductors and preventing surface charge build-up during panel operation. By using a combination of metal and insulator in the resistance layer, the D.C. discharge can be sustained at lower operating voltage, permitting a reduction in the power requirements of the panel.

Metal-insulator-semiconductor capacitors with bismuth oxide as insulator

Abstract: Metal-insulator-semiconductor capacitors using aluminum Bi2O3 and silicon have been studied for varactor applications. Reactively sputtered Bi2O3 films which under suitable proportions of oxygen and argon and had high resistivity suitable for device applications showed a dielectric constant of 25. Journal of Applied Physics is copyrighted by The American Institute of Physics.

Performance of Contaminated Insulators Tested from 200 Kv to 1000 Kv DC

Abstract: The performance of insulators as determined by artificial tests for various contaminant levels at voltage levels ranging from 200 to 1000 kV dc are presented along with comparisons to field measurements. Included are the effects of polarity, insulator shed design, insulator spacing, and uniform and non-uniform contaminant distribution on individual units. The question of linearity of performance with voltage is examined as well as the performance of clean insulators in conditions of fog and heavy rain. Methods of evaluating the ESDD of insulators are also explored.

A Study on the Use of Internal Grading to Improve the Performance of Insulators

Abstract: As transmission line voltages keep increasing, the length of insulator strings has to keep pace. Owingto the non-linear voltage distribution along a string as a result of stray capacitances, the marginal effectiveness of each additional unit of insulator decreases. With an anticipated transmission voltage of up to 1200 kV in the not too distant future, it is likely that the detrimental effects of non-uniform voltage distribution may pose as the ultimate limiting factor. By studying the effect of stray capacitances along a string, it is found that this nonuniform voltage distribution can be reduced by increasing the intrinsic capacitance of each insulator unit. Computer models have been developed as a first step to investigate the effectiveness of using internally capacitivelygraded insulators. Results from these computer studies are presented. These models together with experimental data have been integrated into a computer aided general design procedure which is discussed here. A practical measuring technique for mapping the equipotential field is also described.

The effect of an electric field on contact electrification

Abstract: An applied electric field has a strong effect on the contact charging of an insulator by a metal. However, the experiments reported show that previous interpretations of the effect of an electric field are probably wrong, and that it is not possible to estimate the depth of penetration of charge from observations of the effect of an electric field on contact electrification.

Liquid level detector

Abstract: A liquid level sensor having a pair of upright conductors spaced by an insulator defining a first high resistance path between the conductors. An electrically conductive path is interposed between the upright conductors at a discrete location at which liquid level is to be measured. It includes a liquid accessible gap of a dimension such that the electrical resistance across the conductor when the gap is filled with the liquid is detectably less than when the gap is emptied. The conductor might also be physically altered by temperature changes to serve also as an indicator of elevated temperature.

Development and Application of a Hot-Line Suspension Insulator Tester

Abstract: The paper describes the development and application of a hot-line insulator tester for the detection of defective suspension insulators. Concern over the quality of porcelain insulators and increasing line outage rates has renewed interest in programmed field testing of insulators. Field tests identified a need for a positive method of detecting defective insulators, leading to the development of the unit described in the paper. Initial field trial results using the detector are reviewed.

Stabilized plasma display device

Abstract: A high resolution gaseous discharge display and/or memory device comprises a panel array of bistable charge storage areas designated gaseous discharge cells or sites, each cell having an associated pair of coordinate orthogonal conductors defining the cell walls which, when appropriately energized, produce a confined gaseous discharge in the selected sites. The conductors are insulated from direct contact with the gas by a dielectric insulator composed of a layer of Group IIA oxide doped with a beneficial amount of one or more transition elements selected from nickel, iron, chromium or manganese, to stabilize and control the secondary-electron emission characteristics of the Group IIA oxide under ion bombardment, to eliminate the decrease in the maximum sustain voltage and the bistable voltage margin of the panel during panel operation and to increase initially the bistable voltage margin of the panel, thereby providing stable operating voltages and extending the life of the gaseous discharge display panel. In a preferred embodiment of the invention, the dielectric insulator comprises magnesium oxide doped with 3-5 percent nickel by weight.

Method for manufacturing plastic electrical insulators

Abstract: A method for fabricating a plastic electrical insulator having a fiberglass-reinforced plastic core rod and a plurality of insulator discs disposed thereon The insulator discs are formed of a plastic molding compound which is especially suited for outdoor use In accordance with the invention, the insulator rod is disposed in, and passes through, a mold which, when closed, is filled with the plastic molding compound for forming the insulator discs The separation plane of the mold is situated near the outermost edge of each disc Subsequent insulator discs are individually formed so as to partially overlap a previously molded insulator disc

Gas insulated electrical apparatus

Abstract: A gas insulated electrical apparatus wherein a power transformer and switchgear (4) are contained in a single sealed housing filled with a gas insulator, and the two are electrically connected inside the housing The interior of the sealed housing may be divided by a partition wall (14), so as to define separate chambers for containing the respective devices

Flat type electric discharger for electrophotographic copier

Abstract: PURPOSE:To prevent sticking of moisture and to obviate the change in electric discharge characteristics according to environments by forming either one of electrodes for excitation and discharge of a flat type electric discharger of a resistor for the purpose of heating and applying an electric power source for heating. CONSTITUTION:With an insulator 2 of glass or the like in-between, an exciting electrode 1 formed of a resistor is provided by facing electric discharge electrodes 3 of a rectangular strip shape. An electric power source 5 for heating is also applied to the electrode 1 other than an electric power source 4 for driving, by which the electrode 1 is heated to remove moisture satisfactorily. Thus the sticking of moisture upon the insulator 2, etc. is prevented and the change in discharge characteristics according to environmemts is obviated.

Coil for high voltage rotary electric machine

Abstract: PURPOSE:To increase the lifetime of applying a high voltage to a rotary electric machine and to facilitate a winding work of the machine by winding a thermally shrinkable tape on an insulating tape of a conductor side, thermally shrinking the tape and tightening the tape, thereby preventing the production of a corona discharge. CONSTITUTION:A mica tape is wound and laminated on an interlayer insulator 2 provided on a conductor 1, thereby forming an inner peripheral side ground insulator 3a. At this time, the thickness of the insulator 3a is set, for example, to 1/3 to 1/2 of that of a ground insulator 3. Then, a thermally shrinkable tape 3b is wound on the insulator 3a, and is thereafter disposed in an atmosphere having, for example, approx, 80 deg.C, thereby shrinking the tape 3b to tighten the insulator 3a. Further, a mica tape is wound and laminated thereon, thereby forming the insulator 3c, and a glass tape 4 is eventually wound. In this manner, a corona discharge can be prevented, thereby increasing the lifetime of applying a high voltage thereto.

DC Voltage Distribution Characteristics on Polluted Insulator String

Abstract: Equipment for measuring the DC voltage distribution on polluted insulator strings was manufactured, utilizing opto-electronic techniques, and voltage distribution characteristics were measured through artificial pollution tests

Thermal insulating material

Abstract: This invention relates to thermal insulating material and method of use thereof particularly but not exclusively in relation to insulating cavity walls of buildings The insulator comprises a laminar segment of insulating material (1) provided with a poorly thermally radiative surface layer (2) which is permeable to water vapour In use the insulator may be disposed adjacent the inner leaf of a cavity wall (7)

Manufacture of insulated coil

Abstract: PURPOSE:To obtain an insulated coil for high tension rotating machine having a superior characteristic at a low price by a method wherein insulated elemental wires are transposed and are assembled, and the group of the elemental wires is covered with a porous insulator, a mica tape and a protective tape consisting of a porous insulator are wound around and gap parts are filled up with a thermosetting resin. CONSTITUTION:Plural insulated elemental wires 1 being transposed the level are arranged in a line constitution putting interline insulators 2 between them, the upper and the lower sides are pressed with transposition under members 4 and porous insulators 10 are provided on them. The whole of this line constitution is surrounded with a porous insulating layer 7, and gaps generating at the circumference of the insulators 10 are filled up with a compound 30. Then a mica tape layer 5 is wound around the outer circumference of the layer 7 and a protective tape layer 6 consisting of a porous insulator is wound on it. In this constitution, a thermosetting resin is contained in the compound 30 and a polyester nonwoven fabric or a polyester cloth glass cloth, etc., are used as the porous insulator 10. By this way, the efficiency of work is improved and a coil having a superior electric, thermal and mechanical characteristic can be obtained.

Bundled Conductors in Gas-Insulated High Voltage Power Transmission Cables

Abstract: An improved structure for gas-insulated power transmission cables that employs several subconductors arranged in a bundled configuration is investigated. The study includes electric field calculations, measurements of the breakdown voltages in test lines at different gas pressures, calculations and effects of forces from currents, and an estimation of the heat transfer from the conductors to the outer sheath. The results demonstrate that-compared to equivalent size coaxial lines-the bundled conductor has a lower electric stress on the insulating mechanical supports, is less sensitive to contamination on the spacer surfaces, offers the possibility of trapping contaminating particles inside the bundle, and has a higher heat transfer coefficient

Semiconductor gas sensor

Abstract: PURPOSE:To make a semiconductor gas sensor extremely compact by arranging three conductors on the main surface of an insulator, in which a gas sensitive body is placed between the first and second conductors while a resistance is provided between the second and third conductors. CONSTITUTION:A thick film resistor is printed zigzag on the main plane of an insulator substrate 20 to form a heat generating body 21 while made electrodes 21a and 21b at both ends thereof. Then, an insulating layer 22 is formed on the substrate 20 and the heat generating body 21 without covering the terminals 21a and 21b. Then, thick film conductors 23a-23c are formed on the substrate 20 and the insulating layer 22 while electrode terminals 24a and 24b are respectively provided on each one of the conductors 23a and 23b. Subsequently, detection electrode terminals 25a and 25b are respectively provided on the other ends of the conductor 23b and the conductor 23c. The conductors 23a and 23b are bridged to form a gas sensitive body 26 printed and the electrode terminals 23a and 23c are bridged to form a thick film resistor 27 printed. While the heat generating body 21 gives the sensitive body 26 an optimal temperature for the gas detection, changes in the voltage are detected with the terminals 25a and 25b the moment the sensitive body 26 senses gas. The existence of gas can be found.