CONTRIBUTION A L'ETUDE DE L'INFLUENCE DE LA NON-UNIFORMITE DE LA POLLUTION BASEE SUR LA METHODE DE LA D.D.S.E POUR LE DIMENSIONNEMENT DES ISOLATEURS DES LIGNES T.H.T A COURANT ALTERNATIF

In study concerns the influence of the pollution no uniformity distribution on the calculation of flashover voltage of HVAC insulator linesCette étude s'intéresse à l'aspect de la non-unifromité de la distribution de la pollution sur la tension de contournement des isolateurs des réseaux électrique

Experimental and Mathematical Modeling of the Effect of Insoluble and Low Soluble Salts and Salts Mixture Pollution on DC Flashover of High Voltage Insulators

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Electro-thermal model of DC flashover discharge of Polluted insulator

International audienceThis paper is aimed at the presentation of electro-thermal mathematical model for the calculation of flashover critical voltage (Vcri) and critical current (Icri) of polluted insulator. The used model integrates a particular solution of Elenbaas-Heller equation that has been proposed by Frank-Kamenetski. It also takes into account the pollution resistance and the temperature of the discharge. Different types of electrolytes are also investigated. The Icri and Vcri computed using the relationships we established are found in a good accordance with the experimental ones and the temperatures of the discharge channel deduced from this model are closer to those reported in literature. It also appears from this study that the most important components of the discharge column are water vapour and air is a good approximation; the transfer of metal ions does not have any significant influence

Kidney trauma with underlying renal pathology: Is conservative management sufficient?

To evaluate the pre-existing renal lesions (PERL) found incidentally during evaluation for blunt renal trauma, determine their importance, and suggest guidelines for effective management, including conservative treatment, we reviewed 180 patients who were hospitalized with blunt renal trauma between 1992 and 2008. Thirty of the 180 (16.6%) patients had PERL, which had been undiagnosed. The mean follow-up was 5 years (range 1-9 years). There were 24 men and 6 women with a mean age of 30 years (range 14-80 years). The most common cause of blunt renal injuries was falls and sports. Renal stones were present in 14 patients, pelvi-ureteric junction obstruction in 12, ectopic kidney in two, and megaureter and renal cyst in one case each. Ureteral stenting was used in four cases, and early nephrectomy was required in the other four. Fourteen patients underwent surgery for the PERL and not trauma, with a pyeloplasty in eight cases, partial nephrectomy in three cases, percutaneous nephrololithotomy in two cases, and ureteroneocystostomy in one case. In our study, the conservative treatment was possible in 73% of cases. We believe the published data support increasing conservative attempts in the hemodynamically stable patient

Barrier effect on surface breakdown of epoxy solid dielectric in SF6 with various pressures

International audienceThis paper is aimed at the experimental study of creeping discharges and flashover of cylindrical epoxy solid insulators with and without barrier. The effect of pressure and the shape of insulators surface are discussed. It is shown that the position of barrier with respect to the high voltage electrode affects the flashover voltage unlike its thickness

Creeping discharge and flashover of solid dielectric in air at atmospheric pressure: experiment and modelling

International audienceThis paper is aimed at the study of the propagation of discharge at the surface of solid insulator and the development of an analytical model of flashover in air. The experimental results show that the critical conditions of flashover are met when the discharge reaches the half of creeping distance. Using electrical equivalent circuit and the impedance criterion, we developed a relationship giving the flashover voltage (FOV). This formula evidences the fact that flashover voltage depends on the discharge temperature, the capacitance and the resistance of solid insulator, and the propagation conditions of the discharge. We also show that the computed FOV are in a good accordance with the experimental data

Cap-pin glass insulator simulation and leakage current waveform extraction

This paper presents a simulation of a HV glass insulator and a methodology to extract leakage current signal. Using 3D profiles, COMSOL-based simulations are conducted at a 50 Hz voltage waveform of different magnitudes. The 1512L cap and pin glass insulator is employed since it is widely used in Algerian desert regions. Potential and electric field distributions, along with the temperature rising, are presented and discussed. The current density is extracted and used to compute the leakage current signal. The obtained results are presented and discussed