ACTA TECHNICA CSAV |

On the basis of static definition of the inductance of a closed loop the paper defines the concept of the self-inductance of a single conductor and mutual inductance of two conductors that are used for analysis of multiconductor systems in electrical power engineering. Introduced is also the concept of the total inductance of the conductor following from its voltage that respects all inductive links in the system. Every multiconductor line of a given geometrical configuration can be characterized by an inductance matrix. Derived are matrices of inductance for various types of overhead lines and algorithm for evaluation of inductive links on nonsymmetry of the phase voltages.

Two selected nonlinear control methods are applied to the control of complex drives, in order to compare their characteristics from the view-point of i) elementary requirements such as the dynamics, invariantness, robustness, autonomy, and ii) controller overall structure and its complexity.

A new method for fast selection of faulted phases in a power transmission line is presented. The method is intended for application to modern microprocessor based protective relays and fault locators. The developed procedure for fault-type determination includes fast estimation of symmetrical components of the measured currents. Fuzzy logic reasoning is applied for improving the selection reliability. Already within a quarter of the fundamental frequency cycle after a fault inception, or only slightly slower in certain unfavourable fault cases, the proposed algorithm assures reliable fault classification under diverse specifications of faults and various transmission network parameters. Performance of the developed algorithm has been evaluated with use of the fault data obtained from the EMTP software simulations of diverse transmission line faults. The sample illustrative example of the algorithm operation is presented and discussed. Results of the overall evaluation for varieties of the simulated faults are also delivered.

The paper deals with the problems of securing safely the data transmitted via the systems for the control of railway transport. What is intended is to summarize both the threats and the defence reactions, especially those occurring in open transmission systems. The possibility of using channel coding techniques and cryptography mechanisms is analyzed, following the Standard EN 50159. Finally, the mathematical probability theorems are applied to the determination of undetected errors in channel decoders and in ciphering/deciphering techniques.

The paper presents the results of the numerical
simulation for transformer-switch-*R**C* filter. The transient states are
considered for a one phase circuit of transformer while the main switch is
being opened. The system is designed for reducing both voltage level
increase and magnetic energy dropped.

The main aim of this paper is to present an idea of strategically placed electrodes in Electrical Impedance Tomography to recover the internal structure of the region under consideration. The reconstruction method based on approximating the inverse mapping with Multi-Layer Perceptron neural network. Solution of the inverse problem provides the identification of the radius and the position of the inside object.

The problem of transient processes modeling of transmission lines with distributed parameters using modern programs for electromagnetic transient simulation is considered. The mathematical model of three-phase line is improved taking into account losses and initial conditions. A block diagram for transmission line transient processes simulation in MATLAB/SIMULINK environment is suggested. Transmission line energization with various initial conditions and load is investigated. The comparative analysis of the received results with reference data is carried out and conclusions about created model adequacy are done.

The main task of that paper consists in the solution of some problems of active frequency filtering of the current signals. The RC-active current filters of the first and the second orders, designed using the second-generation current conveyor CCII�, are presented. Those filters of the second order designed using only one CCII�, without positive feedback, have a quality factor £ 1/2. Using that solution the authors have proposed a new model of an amplifier - a Generalized Current Conveyor GCCII. The proposed structures have been tested by means of simulation programme PSpice using macromodels of the GCCII.