There is difficult to imagine modern production of electrical devices without components containing organic substances. This fact is mainly concerned to composite materials, in which the bond component is made of organic substance. The intricate curing reactions have been proceeding during the composites technological curing as well as during the device operation, where mostly the thermal-oxidative reactions, leading to material degradation, occur. For above-mentioned reasons, there is given big attention to the study of the reactions proceeding in the material. Monitoring of the properties and applicability of high-voltage insulating systems containing epoxy resins require knowledge of curing degree of these resins. This curing degree is considered to be the key parameter for quality of materials used for these systems. Application of Differential Thermal Analysis (DTA) for evaluation of curing degree of three-component composite materials (glass fabric, reconstructed mica, epoxy resin) is presented in the article. Used analysis enables to observe characteristic structural parameter – the concentration of reactive particles in organic component of this material. In our investigation, concept of curing reactions courses was obtained as well as the details for determination of optimal curing time of material. These conclusions have been confronted with the other methods such as Thermomechanical Analysis (TMA) or dissipation factor and complex permitivity determination. Based upon these results it is obvious, that the conclusions correspond to one another. Electrical properties of high voltage-high temperature insulation materials depend on the curing degree of the used resin. The new modified high temperature resistant epoxy resins were used in the three-component composite materials. The main objective of the investigation was to obtain the material with the best electrical properties.

The application of the genetic Algorithms (GAs) in the calculation of the optimal power flow (OPF) for active and reactive powers, simplifies more difficulties of the problem. In this case, the mathematical aspect is based on the analogy of the physical and biological processes. This new approach reduces the complexity, which is generally encountered, for the resolution of the optimisation problems. The combination of the decoupled method and GAs obtain a new calculation algorithm of the optimal power distribution. This new approach is more powerful and effective and will be described in this paper.

A development of mathematical models of control systems is a fundamental question during realization of analysis and synthesis tasks. The development is significant nowadays as majority of tasks is solved by mathematical modelling and digital simulations [1 – 8]. In electric power units the motor supplied via inverter forms controlled system. The circuit models are commonly used in mathematical description of electric drives despite the fact that there is a quick development of both field models describing electric machines and simulation methods considering these models. The circuit models include motor, inverter and control system. The mathematical model together with mathematical and numerical studies of induction motor is presented in the paper. The model considers saturation of motor magnetic circuit, the skin effect occurring in bars of squirrel-cage rotor and moment of friction in bearings of motor as a function of rotational speed of rotor. This model reproduces phenomena occurring in three-phase induction machine and may be applied in order to analyze the transient states. It also may be applied for synthesis of appropriate control systems. Digital simulations of starting the induction motor were made using presented mathematical model. Transient responses and trajectories obtained as a result of simulations are given in the paper. The impact of magnetic circuit saturation on induction motor parameters is also discussed.

Transmission lines are a vital link in HVDC transmission systems. Transients originated in the lines themselves (e.g., short circuits, lightning) or originated in the substation equipments (e.g., rectifier, inverter) propagate from one part of the HVDC system to another through the transmission lines. This paper presents a summary of the main transmission line models currently in use for steady-state and transients simulations on an HVDC link. Simulations have been performed comparing frequency and time domains performance of distributed parameters line model and (π ) sections line model. The limitations of these models are explained. General guidelines are suggested regarding the area of applicability of the models in SIMULINK.

Nowadays, software engineering research community pays much attention to the development software design methods. We observe relatively much less attention in the field program test research. Generally, a good test plan enhances not only the reliability but also increases the reusability of the created test plan in the regression testing phase that will follow after implementing the changes into the system. After describing the motivations and the brief theoretical background we introduce the A-shaped model of the Software Life Cycle (SWLC) with emphasis on the change propagation across the design and test plans. This model consolidates the system design and test planning phases across the SWLC. We define relations between tests and tested elements in a form of existence dependencies: all design must have at least one test, and tests without an attached design element may signalize errors. Further we introduce the specification of a system dependence graph for modeling and visualization of dependencies between the elements. This feature is important during the visualization of the change propagation. The results are demonstrated on an example and finally discussion follows devoted to the similar models.

In this paper, a novel vector controlled six- phase induction machine which is fed from six-phase matrix converter is proposed. Though the practical implementation of matrix converter to vector controlled three phase induction motors is limited and still under investigation due to switches devices implementation difficulties and complication of modulation technique and commutation control, but all research works published so far agreed that the performances of three phase induction motors supplied from matrix converters are superior to that obtained using conventional pulse width modulation controlled inverter. Owing to that, we propose in the present work via simulation the application of six phase matrix converter for the supply of vector controlled six phase induction machines. The paper discusses all components used in the simulation, namely the vector control law, six phase matrix converter as well as the mathematical model of a six phase induction machine with electrical angle between any two three phase stator winding equal to 60 electrical degrees. A scalar modulation scheme with three intervals which ensures high performance and meets desired requirements is used for the control of matrix converter. Simulation results obtained are very satisfactory and demonstrate the possibility of using vector control of six-phase induction machine fed from a six- phase matrix converter. We believe that simulation results obtained will be of great benefit for the future practical investigations.