Showing papers on "Partial discharge published in 1975"

Electrical Characterization of a Corona Discharge for Surface Treatment

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.

Breakdown phenomena of long gaps under switching impulse conditions influence of distance and voltage level

Abstract: The influence of the different phases of the discharge on the statistics of the breakdown processes has been investigated in a wide range of gap lengths (from 2 to 10 m) and applied voltage levels. The effect of the field distribution, along the gap and of the overvoltage ratio upon the development of each discharge phase, has been studied and the transition between subsequent phases has been analysed. The experimental results have been compared with theoretical predictions; the satisfactory agreement, which has been obtained indicates that the theoretical simulation of the discharge phenomena is relatively advanced and starts to be useful from a engineering point of view.

Ultrasonic Spectrum Signatures of Under-Oil Corona Sources

Abstract: Ultrasonic techniques are useful for the detection and location of partial discharge or corona sources associated with HV power apparatus, particularly oil-filled power transformers. Measurements are commonly made using narrow-band transducers operating in the frequency range from ~20kHz to ~300 kHz, and occasionally at higher frequencies for which there is little published information. Because of the lack of available data on the spectra of ultrasonic emissions from discharges in oil-insulation systems, an investigation was initiated to determine if there was an optimum measuring frequency and whether discharges could be identified by their spectral characteristics. It was discovered that insulation voids and gap-type discharges, for example, have clearly identifiable ultrasonic frequency characteristics, and the actual physical size of voids may be estimated from their frequency spectra.

Method and system to detrect partial discharge in high voltage apparat us

Abstract: PURPOSE: To provide a partial discharge detector for high voltage equipments that accurately detects partial discharge being produced. COPYRIGHT: (C)1977,JPO&Japio

Compact high voltage feedthrough for gas discharge devices

Abstract: A support structure and electrode design geometry for a compact high voltage feedthrough, which is used in low-pressure gas discharge devices. The high voltage coaxial cable which applies voltages to the various electrodes within the discharge device is fed through an insulating structure and supported therein by means of field shaping electrodes. The space between the field shaping electrodes is filled with an electronegative gas. The electrodes insure that the electrical field lines merge smoothly from the low pressure region, across which high voltage is applied, into the dielectric of the coaxial cable. The structure minimizes local electrical stresses while maintaining a high voltage electrode separation in the low pressure region which is less than that at which Paschen breakdown occurs. The advantage of the present invention is its compactness of size and that it minimizes the probability of vacuum, surface, and bulk breakdown as well as Paschen breakdown.

A variable low frequency high voltage generator using valves with fibre optic light guide control

Abstract: Describes a new method of generating low frequency high alternating voltages by modulating two high voltage DC supplies of opposite polarity. The modulation is accomplished by the use of triode valves situated at high voltage whose grids are supplied by control signals, transmitted from the control circuit through fibre optic light guides. The first generator built is capable of driving a 1 nF load at 10 kV peak over the frequency range DC-50 Hz, or a 0.1 mu F capacitor at up to 0.1 Hz. In order to increase the voltage and current ratings of the generator, a series-parallel arrangement of valves may be used, with the appropriate control signals fed to the grid of each valve. Because the generator is relatively free from any electrical noise, it can be used to energize insulation samples in connection with partial discharge detection investigations.

Creeping discharge and partial discharge prevention means for a coil end of a rotary electric machine

Abstract: A creeping discharge and partial discharge-prevention means for a stator coil end of a rotary electric machine is disclosed. It includes an grounding electrode on an insulator of the stator coil end of the rotary electric machine, a first electrical stress grading coated layer on the insulator of the coil end including the end of the grounding electrode, a shield insulator made of insulation material around the first electrical stress grading coated layer including the end of the grounding electrode, a shield electrode electrically connected to the grounding electrode around the shield insulator, and a second electrical stress grading coated layer coated on the shield insulator including the end of the shield electrode.

Comparative investigations of DC and 60Hz prebreakdown behaviour of vacuum insulation

Abstract: Vacuum insulation for high voltage power apparatus is becoming more acceptable. However, there is very little comprehensive data available for the insulation performance of vacuum gaps under 60Hz a.c. voltage stress. The authors report the result of a systematic study comparing the behaviour of a vacuum insulated gap under d.c. and 60Hz a.c. voltage stress. It is concluded that the behaviour of a vacuum gap is not significantly different for the different types of voltage stress except in the initial prebreakdown phase.

A Solid Insulation System for Airborne High-Voltage Components and Systems

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.

Wide-Band Partial Discharge Detector

Abstract: A wide-band peak voltage detector is presented, which is used for measuring partial discharges in submarine telecommunication cable systems. For high-voltage discharge detection of simple dielectric geometries or complete power filters, the wide-band detector is suitable for laboratory or factory use. A low-cost low-resolution amplitude-distribution analyzer can be assembled by combining several detectors for the special requirements of high-voltage dc testing, at a small fraction of the cost of a commercial distribution analyzer.

Method for electropneumatic conversion

Abstract: In a closed discharge chamber wherein a discharge electrode supported on an electric insulating material and an opposite electrode are arranged to confront each other, a high electric potential applied between said electrodes causes corona discharge to occur in the gas between the two electrodes. A method for control of pure fluid elements, fluid servomechanisms, etc. is disclosed which is accomplished by utilizing a phenomenon that the pressure of the gas within the closed discharge chamber increases in consequence of the occurrence of corona discharge and the increased pressure falls with the subsequent extinction of corona discharge back to the level existing before said corona discharge.

Dielectric breakdown of polyethylene under gamma irradiation

Abstract: The d.c. and impulse electric strengths of high-density polyethylene films, which were recessed and metallised on both sides to prevent external partial discharge, were measured with and without ? irradiation of intensity 1.4×104 r/h, in the temperature range from ?196°C to 110°C. Radiation had little significant effect on the results.

Conduction and breakdown in dielectric liquids : proceedings of the 5th International Conference, organized by the Department of Applied Physics of the Delft University of Technology, Noordwijkerhout, the Netherlands, 28-31 July, 1975

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.

Corona testing of high voltage airborne magnetics

Abstract: Corona testing has been used to screen high voltage magnetics for reliability, despite the fact that the significance of the measurement results is not well understood. This paper examines the fundamental physics involved, and displays a method of determining correct corona specifications.

Dielectric strength of liquid helium impregnated plastic tapes

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.

Breakdown of the near-electrode layer in a flow of ionized gas

Abstract: An electric discharge in a flow of ionized gas is widely used in many physics and engineering problems. Among them are problems associated with current flow in various magnetohydrodynamic devices (generators, accelerators), arc shunting in a plasmatron, physical experiments in shock tubes, etc. It is known that with cold electrodes providing the contact between the plasma and the external circuit and relatively high pressures, two modes of current flow occur: at low current, the discharge is of a distributed nature; as the applied voltage increases, the discharge abruptly shifts into a discharge with a clearly developed cathode spot at some critical current density (we call this form of discharge an arc discharge). Existing experimental data [1–20] refers to varying experimental conditions. Furthermore, the critical voltage (or current) at which the transition of the discharge from a distributed discharge to an arc discharge occurs varies within very broad limits. From an analysis of the experimental data, a condition is formulated which the discharge parameters satisfy at the time of transition from a distributed discharge to an arc discharge.

Theory of gas breakdown in an inhomogeneous field

Abstract: Consideration is given to an independent electrical gas discharge in an inhomogeneous field, with photoionization of the gas as secondary mechanism. The condition for an independent discharge to exist is derived; this condition enables the breakdown voltage to be calculated, and also explains the short times required to form the discharge and the fact that the breakdown voltage is independent of the cathode material. The same condition may be considered as a criterion for the ignition of a self-sustaining corona in a long spark gap with nonuniform geometry.