Showing papers on "Partial discharge published in 1971"
TL;DR: In this article, the electrical discharge characteristics of SF6 are discussed theoretically in relation to the field dependence of the ionization coefficient a and the electron attachment coefficient, and a simple theoretical formulation of breakdown or corona inception voltages of gaps in SF6 is derived.
Abstract: The electrical discharge characteristics of SF6 are discussed theoretically in relation to the field dependence of the ionization coefficient a and the electron attachment coefficient The results are compared with the characteristics of air. A simple theoretical formulation of breakdown or corona inception voltages of gaps in SF6 is derived. The formulation has been examined by experiments on several electrode configurations. At low pressures of less than 4 atm, the agreement of the theoretical and the experimental results is fairly good. The breakdown voltage decreases from the theoretical estimation at higher pressure.
86 citations
TL;DR: In this article, a short gap spacings are observed to occur in particular when dielectric surfaces are involved; the deviations are characterized usually by the appearance of pseudoglow discharges, which exhibit properties that are common to both pulse and glow discharges.
Abstract: Corona discharge results, obtained with a number of gases under atmospheric pressure using plane-parallel metallic and dielectric electrodes placed between 0.05 and 9.00 mm apart, are discussed. With short gap spacings, deviations from the pulse or spark-type discharge mechanism are observed to occur in particular when dielectric surfaces are involved; the deviations are characterized usually by the appearance of pseudoglow discharges, which exhibit properties that are common to both pulse and glow discharges. The practical significance of pseudoglow discharges in relation to corona measuring techniques, utilizing conventional pulse discharge detectors, are considered both on a short-and long-term test basis.
75 citations
TL;DR: In this paper, an investigation into partial discharge in artificial air-filled cavities of known dimensions in polyethylene is described, where the authors show that the 50 percent impulse-inception stress is much higher than the discharge stress calculated from Paschen's curve.
Abstract: An investigation is described into partial discharge phenomena in artificial air-filled cavities of known dimensions in polyethylene. During initial tests, the 50 percent impulse-inception stress is much higher than the discharge stress calculated from Paschen's curve. It is independent of the impulse repetition rate, and is larger for 1/50-?s impulses than for 500/3000-?s surges; for both waveshapes the extinction stress is lower than the inception stress. After repeated discharges, the inception and extinction stresses are both reduced to the Paschen curve value. Initially, the 50 percent impulse-inception stress increases as the cavity diameter is decreased at constant depth and as the depth is decreased at constant diameter. After aging, the stress becomes independent of the cavity diameter. Details are given of the discharge magnitudes and time lags. It has been shown that a "main discharge" occurs usually on or near the crest of the surge, during which all or a substantial part of the cavity is discharged, followed by a number of smaller "reverse discharges" on the wavetail. When a discharge occurs on polarity reversal its magnitude tends to be appreciably greater but it can be reduced by suitable voltage conditioning. Experiments have also been made with the cavity adjacent to an electrode instead of totally enclosed in the dielectric.
38 citations
TL;DR: In this article, the behavior of corona and the resulting damage in oil-filled insulation were investigated, and it was shown that a charge in excess of 1 x 104 pC can be expected to produce damaging corona.
Abstract: The, behavior of corona and the resulting damage in oil-filled insulation were investigated. internal corona should be divided into intrinsic oil corona and bubble corona. The former is far more intense than air corona. The magnitude of the individual charge usually exceeds 1 x 104 pC. Insulation damage barely appears under lx 105 pC. This fact was deduced from investigations of insulation models and experience with actual transformers. With some margin, a charge in excess of 1 x 104 pC can be expected to produce damaging corona. This work will be helpful in interpreting corona test results, as well as in improving procedures for testing corona in EHV transformer's. Some proposals for testing transformers for the presence of corona are presented.
28 citations
TL;DR: In this article, internal discharges were studied in a cylindrical cavity and found to tend to be localized or fractionized from the measurements of apparent charge of maximum discharges, repetition rate of discharge pulses and inner surface resistivity in cavities and from the observation on discharges with a microscope.
Abstract: Internal discharges were studied in a cylindrical cavity. Discharges were found to tend to be localized or fractionized from the measurements of apparent charge of maximum discharges, repetition rate of discharge pulses and inner-surface resistivity in cavities and from the observation on discharges with a microscope. Phenomena of internal discharges are easily influenced by physical properties of the inner-surface of a cavity, especially the electrical resistivity to be subject to change due to the discharge themselves.
23 citations
Patent•
17 May 1971TL;DR: In this article, a corona discharge electrode is supplied with voltage from a high frequency power source to produce a charge which strikes a sheet of reproducing paper to charge the same electrostatically.
Abstract: A corona discharge electrode is supplied with voltage from a high frequency power source to produce a corona discharge which strikes a sheet of reproducing paper to charge the same electrostatically. A detection electrode is positioned in the field of the corona discharge and is connected via a resistor and amplifier to the power source to control the same in accordance with the detected corona discharge to maintain the magnitude of the discharge field constant. A switch is connected in the power supply to interrupt connection thereof with the discharge electrode if a spark discharge is produced between the discharge electrode and the paper.
19 citations
TL;DR: In this article, a second round-robin was run using direct electrodes with the object of surveying some simple testing methods corresponding to actual phenomena such as local perforation by corona.
Abstract: "Round-robin" experiments for partial discharge degradation of polyethylene have been made by means of a parallelplate electrode system. Following this, a second round-robin was run using direct electrodes with the object of surveying some simple testing methods corresponding to actual phenomena such as local perforation by corona. Corona lifetimes of several insulating materials were measured by using two kinds of electrode systems, i.e., a hemisphere-plane configuration and a cylinder plane as recommended by the International Electrotechnical Commission (IEC). Precise differences between different materials cannot be defined because of the fluctuation of corona lifetime of the same material, but there may be some significance in the order of six kinds of materials. Several possible causes of the variability were examined with regard to the differences of test dates, humidities, airflows, and specimens' thicknesses and some information concerning relations between variability and experimental conditions was obtained. These results and considerations should be helpful relative to the adoption of the most reasonable electrode and the performance of test procedure.
16 citations
TL;DR: In this article, the authors describe the practical methods of shielding a high voltage laboratory and introduce a simplified method for shielding calculations which takes into account the effect of the seams, conducting gaskets, short-circuited slots and sound absorbing holes.
Abstract: A modern high voltage laboratory has to be shielded mainly to avoid the electromagnetic disturbances of the partial discharge measurements. The paper describes the practical methods of shielding a high voltage laboratory and introduces a simplified method for shielding calculations which takes into account the effect of the seams, conducting gaskets, short-circuited slots and sound absorbing holes. A numerical example illustrates the results in the case of a large hall.
13 citations
TL;DR: By comparing the variations in AC breakdown stress of butyl rubber-insulated cable with that of cross-linked, polyethylene- insulated cable, the aspects of deterioration caused by impulse voltages were investigated.
Abstract: By comparing the variations in AC breakdown stress of butyl rubber-insulated cable with that of cross-linked, polyethylene- insulated cable, the aspects of deterioration caused by impulse voltages were investigated.
11 citations
TL;DR: The state-of-the-art is such that a variety of sonic and electrical corona location techniques are employed, none of which is completely adequate, but with experience and patience, corona sources can be found as discussed by the authors.
Abstract: Location of corona or "partial discharges" in transformers can be an extremely difficult, costly and time-consuming process, especially if disassembly is required. The present state-of-the-art is such that a variety of sonic and electrical corona location techniques are employed, none of which is completely adequate, but with experience and patience, corona sources can be found.
6 citations
TL;DR: The main reason why high voltage plastic power cables lead to dielectric breakdown is considered the insulation deterioration which is brought about by partial discharges within voids and other anomalies as mentioned in this paper.
Abstract: The main reason why high voltage plastic power cables lead to the dielectric breakdown is considered the insulation deterioration which is brought about by partial discharges within voids and other anomalies. We have taken various measures in order to suppress these partial discharges. Then we got an idea that when some semi-conductive organic material is blended in the insulation material, the surface resistivity of voids in the insulation and between the insulation and semi-conductive layer is reduced. Our study based on this idea produced effectual results. This paper describes the theoretical analysis, fundamental experiments and application experiments to cables and cable joints.
01 Sep 1971
TL;DR: In this paper, the authors show that for real heavy duty applications, mica is the preferred insulation material due to its voltage endurance and corona resistance, and combine these properties with the high temperatures and capability and superior dielectric strength of mica.
Abstract: During the past 8 years, mica has lost ground in its usage growth as compared to the total electrical insulation market. However, this loss has not been to materials that have superior electrical insulating properties but rather in applications which did not need the properties of mica. There is no product on the market that has the voltage endurance and corona resistance of mica. Combine these properties with the high temperatures and capability and superior dielectric strength of mica and for real heavy duty applications mica is the preferred insulation.
01 Sep 1971
TL;DR: The intrinsic electric strength of many insulating solids appears to be in excess of 10 MV /cm as mentioned in this paper, and this region has been measured on thin carefully prepared samples with pulsed voltages.
Abstract: The intrinsic electric strength of many insulating solids appears to be in excess of 10 MV /cm. Values in this region have been measured on thin carefully prepared samples with pulsed voltages. In practical applications, however, design stresses well below this value are used mainly, because of reliability requirements, since volume breakdown may be caused by anyone of a number of factors, at stress values which are only a fraction of the intrinsic electric strength of the material. These factors include thermal instability, electrochemical and electromechanical processes, chemical or thermal deterioration and partial discharge erosion or channel propagation, which latter has probably most influence on the lifetime of dielectrics.
TL;DR: In this paper, the use of the corona discharge mechanism as a means of providing an electrical load for experimental highvoltage low-current dc generators is investigated, such as point-to-plane, coaxial cylindrical, and wire-toplane.
Abstract: The use of the corona discharge mechanism as a means of providing an electrical load for experimental high-voltage low-current dc generators is investigated. The current-voltage characteristics of several corona discharge configurations, such as point-to-plane, coaxial cylindrical, and wire-to-plane, were experimentally obtained and compared with theoretically predicted values. Of all the configurations tested, the wire-to-plane configuration is found to be capable of dissipating the maximum electrical power (nearly 3 kW/m length of wire) and exhibits a wide range of current-voltage characteristics at various pressures, depending largely upon the wire-to-plane spacing.
TL;DR: In this paper, a small air-blast hv circuit breaker was designed for use up to 50 kV and controlled by an electronic unit which can be triggered by a single discharge pulse of selected level and 0.5 mu s width.
Abstract: This note gives details of a small air-blast hv circuit breaker, designed for use up to 50 kV and controlled by an electronic unit which can be triggered by a single discharge pulse of selected level and 0.5 mu s width. The circuit breaker completes its operation within 20 ms of the application of the triggering pulse. The device was designed for use in fundamental investigations into discharge failure of dielectrics where small multisample test arrangements are employed.