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Paper compares three most widely used methods in insulating liquid breakdown prediction: cumulative stress method, stressed electrode area and stressed liquid volume. Breakdowns were measured on Midel 7131 on OTS100AF oil tester with two different electrodes at three gap distances. Prediction capabilities of three methods were tested with respect to results of conducted measurements and research done...
By using the Finite Element Method (FEM), calculation techniques of electric field distribution for AC, DC voltages and DC polarity reversal conditions were developed in oil-pressboard (PB) composite insulation systems. By using PB layered models under HVDC conditions, it was recognized, the electric field distributions were remarkably controlled by PB arrangement in oil. In particular, it was clarified...
This paper investigated the streamer inception and breakdown properties of a mineral oil and a synthetic ester liquid under DC stress up to 100 kV. To observe the effect of tip radius on streamer inception, the point-plane electrodes configuration with a fixed gap distance of 10 mm and point electrode with the radii of 5 μm, 10 μm, 20 μm and 50 μm were used. To observe the effect of gap distance on...
Operation of mineral oil insulation systems at increasingly high electrical stresses is limited by various forms of partial discharge (PD) activity and by positive streamer initiation from highly stressed electrodes. In this paper, the inception stresses and magnitudes of a wide variety of PD common to oil insulation systems are examined, together with the 60 Hz peak and impulse onset voltages for...
Silicone fluids are now being used as an insulator. Watson,2 Hakim,3 and Hosticka4 have carried out some investigations on this liquid. There is still, however, a great deal that is unclear about the breakdown mechanism under high electric field. It is of importance to know the behavior of the current stress characteristic in the region below breakdown, since the breakdown itself in the liquid dielectric...
A number of workers have studied practical aspects of treeing and they have speculated on the mechanism of tree propagation.1–9 Short time electric strength tests under oil frequently produce tree-like patterns, apparently because the discharge channels in the oil behave as needle-like extensions of the electrodes.3 Formation of a branching breakdown channel is also a likely final phase of breakdown...
Although the gassing of electrical oils under stress has been studied for many years and discussed by a number of authors (1–4, 6–8, 10,11), there appears to be no general agreement as to test methods nor even as to the influence of some of the major test variables. Recent work of Basseches and co-workers indicates that various free-radical reagents will greatly reduce the gassing of paraffinic oils...
This work is an extension of that reported in 1950 by E. L. C. Larson and G. M. L. Sommerman. At that time, it was shown that photographic records of impulse ionization in liquids could be obtained, by placing dry photographic paper and impregnated paper pressboard between; disk electrodes, immersing them in the liquid to be tested, and applying a single impulse voltage wave of a magnitude somewhat...
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