Relevance of the topic
Relationship with academic programs
The purpose of
The idea of
Item of work
The practical significance of the expected results
Content of work
Conclusion
List of sources
Introduction
Design and research work to construction of overhead transmission lines (IL) High power (HV) and ultrahigh (IOS), the stresses often made planning organizations to order power or directorates of objects that are constructed.
Design ТL – laborious task, to solve which often involve several units of the project organization. Reconnaissance and planning the route the line runs in the intelligence division, the calculation of wires and cables, placement of poles – a linear unit, for the calculation of the foundation and strength of supports meet the designers – builders. That is why the automation of the ТL should cover the entire technological chain. Effective automation of the ТL is a very urgent task of our time.
Automation provides a rational distribution of functions between man and computer: the designer solves the problem of the creative nature, and PC – formalized the tasks that are implemented as an algorithm.
CAD system overhead HV and EHV (CAD) is composed of technical and documentation systems.
Relevance of the topic
In connection with the conduct of the action on the territory of Ukraine revised EMP, chapter 2.5 "Air power line voltages above 1 kV up to 750kV" Rules for Electrical Installation occurred need to be recalculated in order to improve the calculation of a special subsystem of large transitions in the structure of UD CAD submarine high and very high voltage.
Relationship with academic programs
R & D is one of the areas of scientific work conducted at the department of electrical systems, Donetsk National Technical University.
The purpose of
The purpose of master's work is to develop advanced algorithms for creating CAD programs HV and SHV overhead line that will meet all the requirements of the new edition of PUE.
The idea of
The basic idea of master's work is the development of new mathematical methods of calculation and algorithms for software modules of CAD, improving information management software modules as creating new databases.
Item of work
The subject of research is modern CAD software overhead HV and SHV. The object is a system of automatic design of HV and SHV overhead, improve it.
The practical significance of the expected results
In carrying out the work planned to test how a new edition of PUE affected the building regulations.
Content of work
An important part of the master's work is to develop a method for calculating the wires "Big jumps" linear subsystem CAD TL.
Called''the great transitions''implies moving overhead transmission lines in the plains through the wide expanses of water (shipping and navigational rivers, bays, sea straits and other water obstructions) and in mountainous terrain through the various gorges.
The calculation of a large power line junction is to calculate the overhead wires, which is required to determine the dimensions of the line above the water surface marks or mountainous terrain.
As is known, the so – called mechanical calculation overhead wires, in principle, the approximate or exact methods.
The basis of the approximate method of calculation adopted by the assumption that the wire suspended from two fixed points on the hinge supports of overhead lines (the so – called pivot point) is valid only vertical uniformly distributed along the length of the load (own weight), under which the wire sags like a homogeneous flexible thread. Perfectly flexible string, which is the bending stiffness is zero at this load takes the outline of a catenary, ie, in the usual representation of the shape of a suspended thin chain with a large number of very small units. Curve sagging flexible filament is located in the plane of the load (in this case in a vertical plane) and, therefore, will be flat curve. Due to flexible thread mentioned properties, it can only operate at a distance. Therefore, the external load is a filament only axial tensile force, which at any point is directed at a tangent to the curve of slack (or perpendicular to the radius of curvature).
Thus, the mechanical stress at any point of a flexible string tension and caused only as a pulling force directed along the tangent to the curve sag at a given point. Bending moment at any section of the flexible filament is zero. Theory of mechanical calculation leads in this case is based on the theory of calculating the flexible threads. Of course, the wire is a metal rod or a pair of twisted rods do not have all the qualities of an ideal flexible string and has some stiffness in bending.
Therefore, the curve of the wires remained close in form to the catenary, and the tension in the wire can be caused not only stretching, but in some cases and bending.
Accurate method for calculating the mechanical wire is also based on the theory of slack flexible homogeneous heavy string, the curve which, as already noted, takes the form of a catenary. However, used to calculate the wire this method formulas associated with the equation of a catenary, expressed in terms of hyperbolic functions. Accurate method allows for specified design conditions to determine the degree of error, which is obtained by calculating the approximate formulas that from the practical aspect is valuable.
In some cases the degree of error can be set in advance, the choice of design formulas, but in special cases it is necessary to perform parallel calculations on the approximate and exact formulas. Such comparative calculations feasible to calculate the wire to go through an extensive overhead navigable river, or in determining the slack wire at a line drawn in the highlands, where there are large longitudinal slope.
An example is a calculation of the length of the wire at unequal heights of the points of suspension wires. We denote X0 the coordinate X point string at which the tangent to the filament is horizontal. Given that X=X0,Y'=0
and since we have:
Integrating, we find:
When X=X0,Y'=0 we obtain:
Finally, we have calculated the following expression for the sag in the unequal heights of the points of suspension wires:
Now obtain an expression for calculating the length of wire.
Fig. 1 – Calculation of the length of wire at unequal heights points of suspension wires (animation consists of 9 shots with a delay of 50 ms between frames, the number of cycles of reproduction is limited to 4 th)
The question of the permissible degree of error is solved by a particular design depending on the nature of the route line, in contrast to stocks in the envelope above the ground or crosses facilities.
The main purpose of the proposed method is suitable for the development of practical applications of the theory thread – so – called theory of chains of equal resistance and the development on its basis a number of problems that arise in the calculation of large transitions.
Despite the successes achieved in the development of filaments, the theoretical solutions are not sufficiently wide practical application. This can be explained by two reasons: firstly, the practical application of theoretical solutions prevent certain mathematical difficulties and, secondly, to use the theoretical solutions are required experimental data.
In this regard, the current parallel with the development and improvement of rigorous theories of the thread are highly relevant to develop simple and practically acceptable approximate methods of calculation and further experimental studies.
Existing methods of mechanical calculation overhead wires in conventional flight, and for large transitions has several drawbacks, foremost of which may be formulated as follows.
1) The calculation does not take into account the weight of the struts and tension insulator chains.
2)sag determined by the regulatory combination of climatic conditions on the regulatory temporary and permanent load, which in general may be exceeded.
3)Do not take into account the heating wires of electric shock, as well as additional heating sunlight wires that after installing darken over time.
4) The actual length of the flight may differ from the project, as in the real world there is a change of span length under the influence of external forces at the points of suspension wires on the poles due to the flexibility and support themselves.
5) It should be borne in mind that the adjustment of sag during installation is in a transitional passage. In this case, the wire is on the roller assembly, and supporting garlands are disconnected from the vertical. In this position the sag in the transitional passage differ from those that will, after relaying the wire clips to deaf and bringing garlands to the upright position.
6)There are some difficulties in accounting for residual deformations of the wires, the magnitude of which depends on the relationship here is sag to span length.
7)gravity load wires made of a uniformly distributed along the length of flight, whereas the wind load and the load of snow, ice can be unbalanced and uneven.
8) The depth of laying the foundation to be constant, whereas in reality his deposit may exceed the calculated values.
Conclusion
All these circumstances give reason to believe that the calculation leads to large power line crossings, using the theory of catenary may, under certain circumstances, lead to insufficient reliable results. This fact has formed the basis for studying the possibility of using the theory of chain equal to the resistance in order to solve the design problem of refining the calculation of transmission line conductors of large transitions.
Chain of equal resistance is called a chain of variable thickness, in which the thickness at each point is proportional to the tension and the likelihood of breaking at all points in this chain is the same, the theory ts.r.s. is more stringent than the theory of catenary, and the theory of a parabola is a special case of the theory ts.l. and the theory ts.r.s.
List of sources
- Правила улаштування електроустановок. Глава 2.4, глава 2.5 із зміною №1. – К.: ГРІФРЕ, 2006. – 126
- Ильичев Н.Б. Расчет и проектирование ВЛ, ОРУ и ВОЛС в среде EnergyCS Line/ Н.Б. Ильичев//М.,2007 – С.12–16.
- Матеріали Другої всеросійської науково – практичної конференції 2006г.[Электронный ресурс]. – Режим доступа: www.ohl.elsi.ru/2006
- Ильичев Н.Б. Программный комплекс «EnergyCS Line» V 3.5. Руководство пользователя / Н.Б. Ильичев / Иваново, 2007 – 79 с.
- ЛЭП 2009 – "Розрахунок навантажень на опори та фундаментів"http://www.bsapr.ru..
- ГОСТ. 13109 – 97 "Нормы качества электрической энергии в системах электроснабжения общего назначения".
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Методические указания по контролю и анализу качества электроэнергии в системах электроснабжения общего
назначения. Часть 1.Контроль качества электрической энергии (РД 153 – 34.0 – 15.501 – 00). - Методические указания по контролю и анализу качества электрической энергии в системах электроснабжения общего назначения. Часть 2.Анализ качества электрической энергии (РД 153 – 34.0 – 15.502 – 2002).
- Електроний журнал [Электронный ресурс]. – Режим доступа: http://www.sapr.ru
!!! When writing this abstract the master’s qualification work is notcompleted. Date of final completion of work: December, 2011. Full text of the work and materials on a work theme can be received from the author or his scientific supervisor after that date.