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The rapidly increasing activity in the field of cryogenics has established the need for a precise understanding of the physical and electrical behavior of insulating materials at the very low temperatures involved. Unlike the normal and higher temperature properties which are well-known, there is little background information and accumulated knowledge available to the design and application engineers...
The change in d.c. resistance, capacitance and dissipation factor of insulating materials has long been recognized as a means for following changes in resin cure. Moreover, modern measurement techniques now make possible practical factory control methods using very small electrodes for small encapsulated circuits and other types of electrodes on large cast resin structures.
The electrical failure of contaminated insulation surfaces is caused by surface scintillation — tiny arcs. It is often characterized by progressive carbonization in a number of branching and sometimes interconnected channels often called "tracks." The appearance and nature of tracks is dependent upon the concentration of the contaminant and the voltage stress as well as the composition of...
When the determination of permittivity is made using attached electrodes, it is necessary to know the dimensions of the specimen. The thickness measurement is especially difficult, particularly for relatively thin specimens. For example, when the specimen is 10 mils thick an error of 0.1 mil in the thickness determination will result in a 1 percent error in the calculated permittivity. The difficulties...
In recent years, the increased use of plastics and elastomers as insulation for applications in areas where heavy surface contamination occurs both indoors and out has resulted in the development of tests to investigate the failure of materials under such conditions. Relatively few such tests have become accepted as standard and often even these are considered to be limited in scope or difficult to...
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