Kudryavtsev Andrey

Faculty: The electrotechnical

Chair: Electric systems

Speciality: Electric systems and networks

Theme of final work: Electrical schemes elements models on basis of full similarity

The supervisor of studies:: Kovyazin V. A.

Introduction

        All electrotechnical and radio engineering devices represent electromagnetic devices the main processes in which submit to the general laws of electromagnetism. In any electromagnetic device there is the movement of electric charges inseparably linked with changing in time and space by an electromagnetic field which two parties are electric and magnetic weeding. Electromagnetic processes are accompanied by mutual transformation of electromagnetic energy to other kinds of energy. The exact analysis of these processes described by systems of the equations in private derivatives (the equations of Maksvella), - a problem difficultly solved even in the elementary cases. But the quantitative analysis is necessary for engineering calculations and designing of devices. Therefore there is a requirement for the approached methods of the analysis allowing with sufficient degree of accuracy to solve a wide range of problems. Such methods are given by the theory of electric chains which for the characteristic of electromagnetic processes instead of vector sizes of the theory of the field, depending on spatial co-ordinates and time, enters integrated scalar sizes - a current and the pressure which is functions of time. Connecting among themselves in appropriate way these ideal elements, receive the electric chain approximately displaying electromagnetic processes in any device in relation to interesting conclusions.

The purposes and problems

        The work purpose is creation of software product with name PowerNet, containing full mathematical models of elements of electric chains both allowing to model stationary and transitive modes of electric systems in a dialogue mode.

Urgency

        Theme urgency. Now there is a set of mathematical models of electric systems and their program realisations intended for calculation both stationary, and transitive modes. However in them, as a rule, there is no user-friendly interface. In particular, it can be or the scheme rigidly sewn up in the program inaccessible to change by the user, or scheme input in the table by instructions of numbers of the beginnings and the ends of objects. These lacks considerably complicate calculation of schemes in need of change of their structure. Therefore creation of the programs is actual, allowing to make input of the scheme and modelling of transients in a dialogue mode under control of modern operating systems.

Scientific novelty

        In the beginning of acquaintance with a theme of work I made the analysis of available workings out. The analysis of workings out was made by search of similar materials, articles, models both in the environment of Internet, and in printing and periodicals. After search the conclusion has been drawn that working out of the given problem is actual. All calculations, were made for a long time, besides, in the absence of the exact technics, standard characteristics which had a large supply have been created. In the given work it is supposed to use computer methods of calculation which differ numerical accuracy. Besides, in working out, it is supposed to use more difficult methods of calculation.

Own results

        It is possible to present results of work in the form of drawing. Thus in drawing are specified as a work end result, so separate tops of performance of work.
        In the given drawing under the term «model of the generator, The transformer, etc. »drawing up of the full differential equations for specified is meant Elements, «model of an arch of an alternating current» - creation of such model which reflects processes in an arch.

Drawing 1 - Own results

        In an initial stage of research of an arch of an alternating current I use a usual RL-chain. (Fig. 2) This chain is switched by the switching device (SC). At chain switching-off in SC the arch which has resistance is lighted. Resistance of an arch In initial approach it is possible to present in the form of certain dependence (fig. 3).

Drawing 2 - the Investigated chain

Drawing 3 - Arch model

        At the moment of chain switching-off there is a current throw. This throw of a current depends on a switching-off corner. Eventually the current fades to 0 from a constant of time which parametres R and L define chains. Thus pressure of a network remains invariable. It is possible to track also pressure change on the switch (SC). Pressure on SC till the switching-off moment is equal 0. After rupture of a chain pressure on SC starts to be restored. The day trend (character of change of loading), is a major factor influencing a choice of the most suitable scheme of indemnification of jet capacity. At many enterprises not all equipment works simultaneously, many machine tools are involved all some hours per day. Therefore individual indemnification becomes very expensive decision, at a considerable quantity of the equipment and accordingly a great number of established condensers. The majority of these condensers will not be involved the long period of time. Individual indemnification is most effective, when the most part of jet capacity is generated by a small number of the loadings consuming the greatest capacity long enough period of time. Centralised indemnification is applied there where loading fluted (moves) between different consumers during the day. Thus consumption of jet capacity during the day varies, therefore use of automatic condenser installations is more preferable, than noncontrollable. For research of transients in considered system on algorithm described in the present section the FORTRAN-program is made. The initial information is set in the second block. It includes parametres of equivalent circuits of all elements of the given model, their catalogue data, degree of loading of mechanisms, structure of the working equipment. All parametres are set in the relative units led to basic sizes of one of elements (in this case generator G1). Also the kind, a place, duration of short circuit are set. In the block 3 preparatory calculations of factors of attenuation and the factors showing participation of each of contours in creation are made. Calculation established доаварийного a mode occurs in the block 4 where initial values of all variables are defined. The procedure of payments a mode is described in section. The program basis cycle begins the fifth block. Here matrixes of the left and right parts of the equations, necessary for definition of pressure in scheme knots are formed. The equations for definition of pressure in knots register on the basis of the first law of Kirhgofa for derivative currents in co-ordinates a, b, c for each knot. In the sixth block a method of square roots the system of the equations in common dares. The method of square roots has been chosen thanking its simplicity and speed. In the block 7 the right parts of the differential equations solved in the block by 8 method of Runge-Kutta of the fourth order are formed. Advantage of this method that it combines simplicity with enough split-hair accuracy, is one-stage (to find ym+1 the information only about the previous point xm is necessary, ym), does not demand calculations derivative of function, but only f (x, y) though to calculate this function it is necessary the function some times at various values x and y. Thus concerning volume of calculations the given method is not economic. In blocks 9,10 values of pressure in each knot of the scheme then in the block 11 new values of currents and потокосцеплений taking into account their increments are defined are specified. Further there is a return on the block 6 and calculation on a basis cycle proceeds.

The review of researches and workings out on a theme

        Electric systems and networks "its teachers - Rogozin G. G, Pjatlina N.G., Lapshina N.S., students - Mironenko I.A., were engaged in Artemchuk D.G.Rizin С.L. in researches of the given problem on chair"., Cocks And. В and Lozitsky J.V.Petuhovym A.V. And Lozitsky J. В the way of definition НВЗ by means of the induction gauge of the shaft located perpendicularly to an end face has been offered. You can familiarise with all materials having passed in "reference" section on my site. Researches is engaged also many researchers outside of Ukraine, especially in the researches, concerning the spectral analysis of components of a current of the engine. The special attention was involved with articles of following authors: Cocks of Century С , member IEEE, the Center of electromagnetic safety, Moscow; M'hamed Drif and Antonio J. Marques Cardoso is with the University of Coimbra, Department of Electrical and Computer Engineering; Marian Dumitru Negrea and Pedro Jover Rodriguez is with the Laboratory of Electromechanics - Helsinki University of Technology; A. Stavrou is with the Electricity Authority of Cyprus. It is possible to familiarise With articles in section "library". As to applied application of technologies of the spectral analysis the firm "A and Alpha consulting" is engaged in it. The direction of work of this firm, is a complex of works on audit of a condition and working conditions of an electric and mechanical part of electric motors and the mechanical devices connected with them on the basis of processing of results of monitoring of a consumed current and the enclosed pressure. Performance of monitoring of a current of the working engine during a short interval of time, and the subsequent special spectral analysis of the received data allows to define presence of damages.

Conclusions and research prospects

        At present time the mathematical model ES realised in program PowerNet allows to count: a vector of operating values and the oscillogram of phase currents, pressure, capacities, and also speeds of rotation and the moments describing behaviour of electric cars; symmetric SC and switching an overstrain; start-up modes, and self-start of electric cars. The realised models: the asynchronous car; the synchronous car; the transformer. Elements of equivalent circuits: ideal sources, the resistor, the coil, the condenser. Further introduction of models of other units of power plants and systems is planned.

The list of the used literature

        1. Sivokobylenko V. F, Mezhenkova M. A. Mathematical modelling of electromechanical transients on power plants. - Elektrichesktvo. - 2001. - №4.

2. Sivokobylenko V. F, Mezhenkova M. A. A method of definition of instant values of symmetric making currents and pressure in transitive modes. - Вісник Nats. Un_v "Lv_vska політехніка". Lv_v: Lviv politechnik. - 2000. - №403. - With.

3. Brooms of Century А, the similarity and modelling Theory (with reference to problems электро power). - M.:High school, 1976.

4. Демерчан K.S.modelling of magnetic fields. - S-P.:Энергия 1974

5. Transients in multimachine systems of an electrical supply electric станций:Уч. The grant/sivokobylenko of Century F - Donetsk: DPI, 1984.-116 with.

6. Roschin G.V.Matimaticheskoe modelling of the equations of electromagnetic transients in electrical alternating current cars. - АНСССР, Power and transport, 1971, №4.

7. International Electrotechnical Commission (IEC) Standard. Rotating Electrical Machines. Part 4: Methods for determining synchronous machines quantities from tests. Publication 34-4. Geneva, 1985. - 175 p.

8. Article on company "Vibro-centre" site http://www.vibrocenter.ru/tdm.htm