Aging of metal oxide surge arresters is mainly affected by the high electric stress near the high voltage electrode. It has been observed that the distribution of voltage and electric field along an arrester is non‐uniform. In this paper, the effect of grading ring geometrical parameters is investigated in order to achieve a more uniform electric field and voltage distribution. A 3D finite element method was employed based on COMSOL MULTIPHYSICS software to calculate these latter. The optimal design of grading ring is achieved by minimizing the electric field along the active column of varistors using a reduced number of simulations based on the Taguchi design and a bat algorithm. Initially, simulation results for a single grading ring were analysed. By using an optimal design of the single ring, the electric field is reduced by 42% in the top of the 220 kV metal oxide surge arrester and the voltage distribution can be improved. It was proposed to install an additional ring at the top of the metal oxide surge arrester. Simulation results shows that using of an optimal design of grading rings, the distribution of voltage and electric field along the surge arrester can be made as uniform as possible.
This paper reports on a new approach for optimal design of corona rings on composite insulator. Finite element method combined with the experimental design methodology and Bat optimization method were used in order to minimize the maximum E-field along the insulator length, with the objective of increasing its long-term performance. Corona ring height (H), radius (R) and tube diameter (Dr) are the most important parameters in the design corona rings. They have been evaluated using different techniques and their optimization was achieved by minimizing the objective function using Bat algorithm which is one of the most recently developed nature-inspired optimization approaches. Simulation studies cover potential and electrical field distributions using COMSOL 4.3, which uses a numerical analysis technique based on Finite Element Method (FEM) were done. Reported results show that the optimized corona ring decreases significantly the electric field near its end fittings. That is, potential distribution will be more uniform with the presence of the optimized corona ring. By installing corona ring, the electric field improves about 58.6% compared with the threshold value. The results show that optimization using Bat algorithm as new methodology is efficient for designing corona rings on transmission line composite insulators and it presents more accurate result in finding the best solutions for corona discharges problems.
In this paper, we present an optimisation method based on genetic algorithms and artificial neural networks (ANN) experimental data from artificially polluted insulators for the determination of the arc constants and dielectric properties in the surface. The study of flashover phenomenon in polluted insulators has not yet been described accurately through a mathematical model. The definitions of arc constants are very difficult, which is created in the dry bands when the voltage exceeds its critical value. In this work, a pollution flashover generalised model is used. The obtained results show that the mathematical model with optimised arc constants simulates accurately the experimental data and corroborate the inverse relationship between flashover voltage and pre-flashover leakage current. For this purpose, an ANN was constructed in MATLAB and has been trained with several MATLAB training functions, while tests regarding the number of neurons, the number of epochs and the value of learning rate have taken place, in order to find which net architecture and which value of the other parameters give the best result. To validate our method an experimental tests for different insulators show very good agreement with the measured values and the computed ones.
In this work, the effect of heating rate and mechanical activation on the reaction of kaolin and aluminium powder was investigated. A batch comprised of 89.5 wt% kaolin and 10.5 wt% aluminium powders was mixed and milled in a planetary ball-mill for 1, 5, 10, 20 and 40 h. The mixture powders were heat treated with a heating rate of 5, 10, 15, 20, 30 and 40 °C/min, respectively. After milling for 20 and 40 h, the results showed the formation of free silicon, quartz and nacrite (Al2Si2(OH)4) at room temperature. The kaolinite dehydroxylation, aluminium oxidation and the θto α-Al2O3 transformations are highly affected by heating rate and mechanical activation. As compared with the smallest heating rate, the mixtures heated with faster heating rate show the disappearance of the peak corresponding to the oxidation of aluminium and the appearance of a second peak corresponding to the formation of α-Al2O3. The intensity of the last peak increases with increasing of the heating rate and milled at lower milling time. The effects of heating rate in the reaction of kaolin and aluminium powder are attributed to the amorphization of kaolinite, the diffusion of Al 3+ to form an amorphous alumina layer on the particle surface and the generation of microcracks at the particle surface of aluminium powder.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.