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Electrical discharges in various gases may produce chemical species which can cause damage to solide surfaces of different materials. In air, for example, ozone, metastable states of molecular oxygen, atomic oxygen and nitrogen oxides are produced. Furthermore, in the case of corona discharges,those species are pushed in preferred directions by electrical wind. As a matter of fact, in the case of...
The advantages of direct-current (DC) over alternating-current (AC) for the transmission of electric power have long been recognized. Considering the transmission line per se, and neglecting terminal equipment, the advantages of DC are overwhelming, and include the following: 1. Improved utilization of the transmission corridor or cable. 2. Complete control over power flow. 3. Absence of phase-angle...
This paper describes partial discharge tests and evaluations made by Philadelphia Electric Company on solid dielectric extruded cables which were giving unsatisfactory service. Both theoretical calculations and actual measurements are presented and are related to the analyses of the causes of poor cable performance.
Several types of thin-film plastic insulation are being evaluated for possible use in ac superconducting underground transmission cables. The materials include polyolefins, polycarbonates, polysulphones, and nylons, in thicknesses ranging from 25µ to 125µ. Multiple-layer samples of the films are placed between 9.5 mm diameter, spherical stainless steel electrodes, and the film and electrodes encapsulated...
Dielectric high potential testing under partial vacuum can measure or determine the minimum air gap distances between uninsulated inaccesible parts which are inside electrical apparatus such as motors and transformers without exceeding voltage limits for the solid insulation of the system.
A modification or the Cleveland Open Cup Test, ASTM D92, was developed for dielectric fluids in non-fire hazard power capacitors and transformers. This was on the basis of considering fire situations in these apparatus. Two criteria for non-flammability were deduced and applied in this test: that burning may only be initiated at the boiling point, and that burning cease on cooling when separated from...
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