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The conduction of electricity in solid dielectrics is an exceedingly complicated phenomenon, and is usually influenced by the chemical, structural, and physical nature of the specimen. Results of experiments on various substances are often chaotic; the considerable lack of correspondence between specimens of the same kind is attributed generally to differences in chemical composition etc. and to differences...
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Previously reported measurements on the high dielectric constant polymer, cyanoethylcellulose, (C. W. Lewis and D. H. Hogle, J. Polymer Science 21, 411 (1956).) have been extended to a wide temperature range with material of three different degrees of substitution. Dielectric data from −76°C to 150°C over a frequency range from 25 cycles to 45 megacycles has been obtained from mono-(6.5% N), di-(10...
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This paper deals with latent damage that consists of “trees” formed by partial breakdown of defective or locally overstressed regions. This cannot be observed in opaque insulation like rubber, but the discovery of trees in polyethylene stimulated interest in this phase of study. Figure 1 shows trees in various stages in contaminated PE after 21 months at 68 volts per mil AC. They start from the conductor,...
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A systematic investigation of the electric strength of nitrogen gas has been made under conditions where the gas density was continuously increased by pressure change from the ambient value to a density approaching that of the liquid state. Such a study is of interest for several reasons: (1) the increased sparking potential makes the use of pressurized gases very attractive for the insulation of...
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A simplified method and a new slotted line have been developed for the measurement of the dielectric constant and loss of solid insulating materials in the 200 to 5000-Mc frequency range. The basic method is a modification of that previously described by Roberts and von Hippel(1) and Dakin and Works(2).
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A high voltage Schering bridge with broad band differential amplifier and cathode ray oscillograph have been used to study the deterioration of Mylar and polyethylene in voids of known dimensions, and in natural voids in polyethylene.
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The accurate measurement of electric breakdown strength in the liquid phase has become possible through the use of short pulse techniques, (1,2,3) and such methods of measurement are by now widely used. On the other hand, the measurements of conduction currents in insulating liquids have continued to rely upon d.c.,(2,4) presumably because of the experimental difficulties inherent in making accurate...
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This paper describes four methods of studying corona spaces in high voltage cables, principally polyethylene cables. These involve: A. The manometric test for corona around the conductor B. Silver mapping on the conductor C. Capacitance increase when the conductor spaces are filled with water D. Change in corona level produced by gas substitution Test A depends on the pressure decrease caused by absorption...
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Oxidation and evaporation are two of the mechanisms by which insulation deterioration have been described. The present tests were made with the idea of showing their relative effects and to study the possibility of acceleration of these effects to give more rapid evaluation of various materials. The materials investigated are black varnished cloth, phenolic impregnated Kraft paper and silicone rubber...
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The Air Force program on high speed, long range aircraft and missiles is seriously hampered by the unavailability of special-purpose materials. In no area of application is the shortage felt more keenly than in the area of electrical and electronic materials.
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Presents the table of contents/splash page of the proceedings record.
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Presents the front cover or splash screen of the proceedings record.
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Provides a schedule of conference events and a listing of which papers were presented in each session.
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When gas voids in solid dielectrics break down under the application of an electric field, the current flow (as observed in the external circuit) is discontinuous, usually consisting of very short (ca. 10−7 sec) pulses. This general behavior is not unexpected, since the charge produced by breakdown of the gas cannot flow through the solid insulation, and therefore reduces the potential across the...
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The rates of hydrolysis, oxidation and thermal degradation were studied as functions of temperature, relative humidity and film thickness. The rate of hydrolysis was found to be very much faster than the rates of the other two reactions. A relation between extent of chemical degradation and physical degradation has been established and the effect of both on electrical properties is shown. Using these...
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Some of the more interesting effects of non-uniform electric fields are described in this report. Experimental and theoretical studies show the effects to be rather striking for particles larger than molecular size. The results show that the effect can be used to produce a fairly efficient pumping action of non-conducting liquids, to cause continuous and easily measureable separations in coarse suspensions,...
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In radiation fields where reliability is essential, silicone insulation systems should be considered for electrical and electronic equipment. This conclusion is based upon a study of the dielectric properties of silicones during and after irradiation.
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Two years ago a paper was presented at this Conference describing the development of organic insulations which will not form carbonized tracks upon exposure to surface electrical arcs. The present paper discusses in detail the proposed internal oxidation mechanism and shows that hydrated alumina compounded with organic materials in specific quantities, is wholly effective in preventing carbonization...
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Hickam(1) has shown that at extremely low pressures (10−4–10−5 mm) the electron capture curve of SF5 is dependent on the temperature at which the experiment is conducted. Experiments were performed to see if there was a temperature effect on the breakdown of SF5. In non-uniform fields, the positive direct voltage for breakdown in SF5 as a function of pressure goes through a maximum. The reason for...
