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In the paper, some cases of using HV insulator in SF6 gas medium are discussed. Computations, permitting to optimize the insulation system geometry and to make use of the HV insulator in atypical constructions, were carried out. The equipotential lines and diagrams of the electric field strength, enabling to draw conclusions concerning shapes of constructions are presented.

In the paper, research results on applying field methods in the process determining the parameters of a current transformer equivalent circuit have been published. The metrological characteristics were determined by solving a non‐linear electrical circuit, that is, the equivalent circuit of a current transformer, assuming different values of the forcing current and load. The method gave satisfactory results (the curve 1 in Figure 1) but was found to be time and labour‐consuming. The determination of non‐linear characteristics of RFe and Xµ elements of the equivalent circuit of a current transformer, using field methods, required carrying out a number of calculations of field distributions at the current transformer no‐load state, with different forcing currents and allowing for the magnetization characteristic of the core as well. The total magnetic energy at no‐load state is related to the main flux which permits to determine the Xµ magnetizing reactance, for a given saturation state of the core. On the basis of the calculated distribution of the vector potential, the Bmax magnetic flux density may be calculated in each element of the core and then, the total core losses and the RFe resistance may be calculated using the p = ƒ(Bmax) characteristics of the core sheet loss. Using field methods makes it possible to determine the X2r leakage reactance of the secondary winding, on the basis of the magnetic energy related to the leakage flux of the secondary winding, independently from the shape or localization of the core and the windings as well, while using the analytic method, the formulas used are true only for cylindrical coaxial windings located on the same column of the core. These formulas have been derived with the assumption that the distribution of the flux in the gap between the windings is uniform and that the flux is divided equally between the primary and the secondary windings, which is not true actually. The obtained characteristics of the RFe and the Xµ non‐linear elements, approximated by n‐degree polynomial, and also X2r were used as the input data for solving the non‐linear circuit, in order to determine the error characteristics.

Problems of correct estimation of metrological characteristics of current transformers based on constructional data and working conditions are of great importance. Applying the commonly known equivalent circuit of the current transformer requires its parameters to be determined correctly. A method for determining the equivalent circuit parameters of a current transformer, based on its field models, is shown in this paper. The results obtained using field computation and real‐life model tests are compared.

The purpose of this paper is to discuss the operation of new generation electromagnetic current-to-voltage transducer. The aim of research was analysis of behaviour of considered current-to-voltage transducers during operation. The main problem was to estimate whether the external fields are able to change the value of the secondary voltage and that the replacement of the casing material by a conductive or ferromagnetic material will increase the immunity of the transducer to external magnetic fields. The immunity of current-to-voltage transducers to the external fields is very important because it influences the proper functioning of the protection system.

The use of analytical methods to assess the influence of external fields was impossible due to the complexity of the geometry. The 3D computations were necessary because of different cross sections of circuit boards at different heights. Therefore the numerical 3D field-and-circuit method based on finite element method was applied. The wide range of dimensions in computation system, ranging from 0.15 mm (print paths) to 0.22 m, made it necessary to use the mesh of millions of elements. The division of this type of system into elements requires a diverse and extremely dense mesh in the area of printed circuits board (PCBs).

The 3D analysis of magnetic field distribution was performed for different external field effect upon a current-to-voltage transducer. The magnetic field distributions and the induced secondary voltage for several different cases were presented. As a conclusion it can be said that in this particular case the magnetic shield is most effective. The influence of external magnetic fields caused by currents passing through the other neighbouring phase bars near are insignificant for the transducer with non-magnetic core.

Commonly used in measuring and protection systems of the transmission lines are induction instrument transformers. The instrument transformers are very precise devices and their errors are counted in tenths of a per cent, and phase displacement of signals in minutes. Especially in HV systems they are very big and their cores are heavy. Replacement of instrument transformers by the current to voltage transducers cooperating with electronic measuring systems will reduce the size and cost of devices.

The requirements set for protective current transformers concern the transformation of currents, with high accuracy, especially at transient states. Therefore magnetic characteristics of their cores should be linear. It causes that cores are large and have some air gaps. Current-to-voltage transducers based on Rogowski coil are particularly suitable for the replacement of the protective current transformers because of their linearity. The traditional technologies used for making Rogowski coil consisted in winding a wire on a non-magnetic carcass. The development of technology has enabled the use of new technologies PCB high density interconnect in the production of Rogowski coil.

The purpose of this paper is to consider a constructional solution of the combined instrument transformer: constructed so that the voltage part is a column transformer, which means that the magnetic circuit of it is open and situated into a composite insulator. The aim of this research was to achieve optimal configuration of open magnetic circuit of the column voltage transformer.

The authors made analyses of electromagnetic field distribution and computed the voltage error and phase displacement for many different cases of magnetic circuits of the column voltage transformers. The analyses of the electromagnetic field distribution and computations were carried out using the 3D field‐circuit method based on the finite‐element numerical method. The results were compared with tests of a real‐life model.

The result of research is the selection of the best constructional version of the column voltage transformer; the research also gives some guidelines for design and manufacture of this construction of combined transformers.

The paper is meant for constructors of instrument transformers and presents results of research into new constructional solutions of combined transformer.

The purpose of this paper is to present a new approach for the optimal design of protective current transformers (CTs). The proposed technique is applied to the design of typical CTs and results are compared with traditional CT design method and genetic algorithm optimization algorithm.

The aim of CT design is to make current measurements more accurately, particularly for the high fault currents which arise in short circuits, and more efficient CT in terms of both size and cost. The present work formulates these objectives as an optimization problem to be solved by particle swarm optimization.

Simulation results demonstrate the effectiveness of this technique in optimizing the CT design parameters. The designed CTs have smaller measurement errors compared to standard values and respond well to high fault currents. Manufacturing costs have also been reduced.

In addition to improved efficiency, the benefits of this method are its treatment of CT design in terms of an equivalent circuit and design parameters. The proposed algorithm also extends the linear operation area of the CT and guarantees its good response to high fault currents that may occur in power systems.

This paper aims to develop a model that reflects the current transformer (CT) core materials nonlinearity. The model enables simulation and analysis of the CT excitation current that includes the inductive magnetizing current and the resistive excitation current.

A nonlinear CT model is established with the magnetizing current as the solution variable. This model presents the form of a nonlinear differential equation and can be solved discretely using the Runge–Kutta method.

By simulating variations in the excitation current for different primary currents, loads and core materials, the results demonstrate that enhancing the permeability of the B–H curve leads to a more significant improvement in the CT ratio error at low primary currents.

The proposed model has three obvious advantages over the previous models with the secondary current as the solution variable: (1) The differential equation is simpler and easier to solve. Previous models contain the time differential terms of the secondary current and excitation flux or the integral term of the flux, making the iterative solution complicated. The proposed model only contains the time differential of the magnetizing current. (2) The accuracy of the excitation current obtained by the proposed model is higher. Previous models calculate the excitation current by subtracting the secondary current from the converted primary current. Because these two currents are much greater than the excitation current, the error of calculating the small excitation current by subtracting two large numbers is greatly enlarged. (3) The proposed model can calculate the distorted waveform of the excitation current and error for any form of time-domain primary current, while previous models can only obtain the effective value.

This chapter focuses on the special education system of education in Poland since the transformation of the political system in the late 1980s. The move from segregated settings toward more integrated settings for students with low-incidence disabilities is described along with the new structure of special education identification and classroom settings. Current strategies and support for students with high-incidence disabilities in Poland who are placed in general education and special education are discussed. Ideas on how to improve the existing system are outlined and solutions are presented. Overall, the implementation of educational reforms brought about positive changes in educational settings for most students identified with special needs in Poland. Due to this emphasis on inclusion, more students with high-incidence disabilities have the chance to succeed in integrated schools with adequate support.

The combined current‐voltage instrument transformer (CCVIT) is a complex non‐linear electromagnetic system with increased voltage, current and phase displacement errors. Genetic algorithm (GA) coupled with finite element method (FEM‐3D) is applied for CCVIT optimal design. The optimal design objective function is the metrological parameters minimum. The magnetic field analysis made by FEM‐3D enables exact estimation of the four CCVIT windings leakage reactances. The initial CCVIT design is made according to analytical transformer theory. The FEM‐3D results are a basis for the further GA optimal design. Compares the initial and GA optimal output CCVIT parameters. The GA coupled with FEM‐3D derives metrologically positive design results, which leads to higher CCVIT accuracy class.

To investigate the use of amorphous iron as the stator core material to increase the efficiency of electric machines in serialised production.

In the design process of a new structure for the induction motor with a stator core made from amorphous iron it is necessary to apply the circuit method and the field‐circuit method. The use of the circuit method allows quick calculations of many versions of the designed motor, but the use of the field‐circuit method is necessary for verification of the maximal value of the flux density in the entire area of the cross‐sections of the motor core.

A new construction for the small induction motor with the stator core made from amorphous iron was designed based on the classical structure of the four‐pole induction motor. In the designed motor a decrease of the electric energy costs was observed, which is much bigger than the material costs, and in effect lower total costs for the designed motor were obtained.

According to necessary changes in the motor construction, due to lower saturation limit for this material, the authors obtained a significant increase in the motor efficiency and a decrease in the total cost of the motor. The development of a new technology allows the cutting of amorphous magnetic materials and the production of electric motors from them.

This paper shows the possibility of using amorphous magnetic materials for stator core of small induction machines and the advantages of such construction for obtaining more efficient motor construction.