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Insulators are very important elements of electric power systems. This paper introduces an analysis of electrical conditions in the area between the conductor and the insulator's upperfitting. The designing of new a composite post insulator is presented with the upperfitting made of insulating material. Previous composite post insulators have had upperfittings made of conducting material metal. 3-D analysis of electric-field strength in the insulator and its surroundings are also given. The computation was carried out by using the OPERA Vector Fields program tool. The results of this analysis are presented for both--new and old versions of a composite post insulator. 3-D analysis shows that the new version has up to five times lower magnitudes of electric-field strength. Index Terms--Electric field, electric-field strength, finite-element method (FEM), medium-voltage post insulator, partial discharge.

This paper introduces a new method for evaluating the status of medium-voltage (MV) switching devices by defining two hybrid parameters. The device condition hybrid parameter (DCHP) and the device importance hybrid parameter (DIHP) are defined by using weighing factors. Three different methods were applied for determining the DCHP, while the DIHP is determined by using the differential evolution algorithm. Boundary values for the DCHP are calculated on the basis of economic criterion regarding minimum costs. The proposed approach was primarily developed for applying modern MV switching devices maintenance, but can also be used in network planning and for proper choosing of MV switching devices. It is elucidated by an example. Index Terms--Costs, maintenance, medium-voltage (MV) network, optimization, switching devices.

This paper presents application of multiobjective optimization methods on a capacitive divider finite element model. Modeling is based on the differential evolution algorithm (DE), including the concept of the Pareto nondominance. Through calculations, this concept allows differential evolution algorithm variation in order to achieve uniformly distributed results on the Pareto front, including the lowest population size as possible. Selection step, as a part of the differential evolution method, is properly modified to improve the convergence of the algorithm. The entire research leads to a hybrid algorithm development. Index Terms--Epoxy resin insulators, optimization methods, Pareto distributions, voltage dividers.

This paper deals with the modeling of a low-voltage gas discharge arrester using the MATLAB/Simulink program tool. The model is designed to enable a combination with other overvoltage protection system elements (metal-oxide varistor, supressor diode) in order to put a model of an integrated overvoltage protection system together. This model comprises all phases that may appear during the operation of a gas discharge arrester. Therefore, it consists of five main submodels, each of them representing one physical phenomenon. The results obtained by performing model analyses within the MATLAB/Simulink program tool were verified by laboratory tests with various voltage sources (lightning surge voltage, ac voltage, and combinations of them), performed on real gas discharge arresters. Index Terms--Electric arc, gas discharge arrester, MATLAB, overvoltage protection, surge arrester, Toepler equation.

This paper describes the impact of selected insulation elements and the surrounding material, on the magnitude and distribution of electrical potential in a switch device. The procedure is based on finite element method numerical analysis and stochastic optimization algorithm of differential evolution (DE). The optimal selection of mutually independent insulation materials has an impact on the control of potential and, consequently, on dielectric strengths, both inside the bushing and in other switchgear elements. Two different methods are used for an extension of the multiobjective optimization of the problem. The entire modeling procedure also includes optimization of the bushing's geometrical shape. Index Terms--Finite element methods, gas insulated switchgear, insulators, optimization methods.

In this paper, we present how the finite-element method can be utilized to analyze the influence of an additional substance in the trenches surrounding the grounding grid's conductors on the grounding grid's performance. For this purpose, we modified the preliminarily existent FIELD_GS program code in such a way that the additional substance in the immediate vicinity along the grounding grid's conductors can be simulated. Different soil structures and various volumes of the additional substance in the soil have been analyzed to prove the suitability of surrounding the grounding grid's conductors in trenches with the additional substance. Index Terms--Electromagnetic fields, finite-element method (FEM), grounding electrodes, numerical analysis.

Modern design of medium-voltage switchgear insulation elements is based upon the use of optimization methods. This paper presents an algorithm for the design of such elements using numerical calculations on the basis of the finite elements method in connection with evolution optimization methods. The use of differential evolution and evolution strategy algorithms is presented in the case of modeling a medium-voltage post insulator, the secondary function of which is voltage indication. A comparison between these two algorithms is also presented. The task of both optimization algorithms is to find an adequate capacitance of the voltage divider and the optimal distribution of electric field strength. All other requirements and constraints that have to be taken into consideration in the design of insulation elements are also included in the algorithm. Index Terms--Finite-element method (FEM), high-voltage techniques, optimization methods, switchgear.

Recently, in medium voltage overhead line systems, previously bare conductors are being replaced with conductors covered with a layer of insulation. Covered conductors enable an economical increase in operational reliability. At the current stage of development, there are several ways of replacing bare conductors with covered ones. Such a replacement also requires changing the accompanying line accessories, insulators, and line protection devices. The selection of the optimum combination of covered conductors and equipment has been done by means of electric field calculations. The optimization parameters have included the use of existing equipment to the maximum possible extent, new elements of equipment that have to be added, and the prevention of disturbances and failures in operation. Theoretical findings have been confirmed with laboratory tests on prototype combinations of covered conductors and the accompanying equipment. Index Terms--Covered conductor, electric field, finite element method, medium voltage overhead line, partial discharges.

This paper describes theoretical and practical work in the development of medium voltage metal-clad switchgear with metal partition walls. Special attention was paid to achieving the optimum shape of the electric field in the switchgear using the lowest possible electric field intensities. The sizes of the switchgear, and the insulating and conducting elements have been defined using the electric field calculations. The switchgear has been made and tested in the laboratory according to these sizes. The results obtained have also served for calibration and confirmation of the method and mathematical model of the electric field calculation. Index Terms--Bushing, electric field, finite element method, medium voltage metal-clad switchgear, metal partition walls.

This paper describes ensuring safe working conditions for workers performing electrical installation work and maintenance on overhead lines within the vicinity of high voltage. Due to harsh operating conditions and the necessity of ensuring uninterrupted electricity supply, it is sometimes necessary to replace a conductor on a double-circuit overhead line with one circuit for normal operations. In such cases, there is a high-risk of conductor swing that may cause contact with the phase conductor of the adjacent energized circuit. The presented special “sliding grounding clamp” has been designed and constructed in order to carry the fault current to ground. It enables a good flow of the current from the drawn conductor and, thus, protects the workers from excessive “step and touch” voltage on the worksite. The sliding grounding clamp has been constructed, and tested in practice. It has also been granted a Slovenian national patent. [ABSTRACT FROM PUBLISHER]