Articles you may be interested inSemiconductor core-shell quantum dot: A low temperature nano-sensor material

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Experimental results and analysis about the behavior of ethylene propylene diene monomer (EPDM) class 15 kV type suspension insulators exposed to an acid environment and an altitude of 2240 mas1 are reported. An aqueous solution with the principals ions present in the most acid rain registered in the Valley of Mexico was used. The fog clean method developed for non ceramic insulators (IEC-507) was utilized, but with the difference in the manner of applying the pollutant mixture on the surface of insulators. For evaluate the loss of hydrophobicity the technique of contact angle was used. The flashover voltages and the behavior of accumulated charge are analyzed. The results show a strong reduction of the hydrophobicity on insulators previously exposed to acid rain.

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The humidity correction factors specified by IEC Publication 60-1 (1989) and IEEE Std.4 (1995) for impulse voltages are restricted to 1 2 h/6 < 15. However, values of h/S 2 15 g/m3 in many regions of the world are present. The IEC-60 and the IEEE Std.4 procedures are based on the macroscopic observation that the atmospheric correction factors are larger when the discharge is governed mainly by positive streamers;while they tend to be lower when leaders or negative streamers are present. A better atmospheric correction factor implies to study the influence of atmospheric parameters on each discharge mechanism of the breakdown process. In this paper for standard lightning impulse voltages an analysis of the influence of absolute humidity divided by relative air density (his) greater than 15 gr/m3 on the positive streamer predischarges is reported.

The designers of microwave devices in the industry use the analytical solutions of the corona discharge equation to determine the minimum power breakdown threshold, in a particular device, such as waveguides and filters, and know whether it is in the established margins. There are two main ways to determine the breakdown threshold of a waveguide analytically; the most commonly used describes the plasma density generation completely as a function of the geometry by using the characteristic diffusion length, while the second is a more thorough method that involves the use of the effective diffusion length which considers collision frequency and electric field into the equations. Hence the aim of the designers is to obtain the closest results to experimental results, both methods must be considered in addition to the environmental changes so that they know the operational limits. This chapter describes the different methods to obtain analytical results for the breakdown threshold in any rectangular waveguide device, the influence of environmental conditions in the analysis and the inhomogeneous electric field effect inside the devices.