Son gelişmelere göre bilgisayar destekli enerji iletim hatları tasarımı

Abstract

Bu tez çalışmasında,"Son Gelişmelere Göre Bilgisayar Destekli Enerji İle tim Hatları Tasarımı" adı altında, enerji iletim hatları tasarımı konusunda yapılan son incelemeler araştırılmış, varılan sonuçlar değerlendirilmiş, bazı bilgisayar çalışmaları sunulmuş ve sonuç olarak direk tasarımında yükler konusunda bir bilgisayar programı üzerinde çalışılmış ve hesaplamalar yapılmıştır: Bu arada konuyla ilgili temel bilgilere de kısaca değinilmiştir. Bu çalışmada elimizde bulunan Türkçe kaynaklardan bir derlemeden ziya de yabancı kaynaklardan özellikle de son makalelerden yararlanılmıştır. Bilindiği gibi konu oldukça kapsamlıdır ve üzerinde ciltlerce kitap yazıla bilir. Burada diğer tüm konulara değinilmekle beraber enerji iletim hatları tasarımında direkler ve yüklemeler konusuna ağırlık verilmiştir. Bu bakımdan önce direkler hakkında kısa tanıtıcı bilgiler toplandıktan sonra çelik konstrüksiyonlu direk tasarımı için enerji iletim hatlarında bilinmesi gereken temel ve pratik bilgiler ayrıntılı olarak verilmiştir. Bu bölümde yüklemeler konusuna özellikle önem verilmiş, enerji iletim hatları ta sarımında rüzgar yönü ve aşın rüzgar yükleri konusunda son gelişmeler ve çalışmalar anlatılmış, yapılan uygulamalar ve sonuçlan verilmiştir. Direkler ve etkileyen faktörler incelendikten sonra direk kısımların kuvvetlere karşı dayanımı incelenmiş, direkleri bağlayıcı elemanları hakkında bilgi verilmiştir. Direklerin testleri, temeller, hat tasarımındaki etüdler ve iletim hattının inşaası hakkındaki pratik bilgiler ile bölüm tamamlanmıştır. Konuyla ilgili iki uluslararası kuruluş IEC ve CIGRE araştırma komiteleri tarafından yapılan, son gelişmelere göre enerji iletim hattı tasarımı konusundaki araştırma ve sonuçlarının ardından konuyla ilgili yapılan bazı bilgi sayar çalışmalarından tanıtım ve örnekler verilmiş yine optimizasyon konusunda son çalışmalar, gerekli veriler ve sonuçlarla metin kısmı tamamlanmıştır. Son olarak çelik kafesli bir direk tasarımındaki yükler konusunda bir bilgisayar programı üzerinde çalışılmış ve hesaplamalar yapılmıştır.

In this study, under the title of "Transmission Lines Design according to Recent Advances with Computer'' recent researchs on Transmission Lines Design have been studied, the results obtained have been evaluated, some informations from computer researchs have been given and as a result, a computer program on loads on steel- constructed towers (in 154 kV) was gi ven with its outputs and list. As its well known, complete subject (Transmission Line Design) is very complicate. In this study, althought all other matters were touched, Tower design on transmission lines was basically intensified. Therefore, firstly, ge neral information on towers were given and then required basic and practi cal information on transmission lines for design of steel transmission towers were given with details, This section consists of an orderly presentation of facts on a particular subject, supplemented by an analysis of the limitations and applications of these facts. It contains information useful to the average engineer in his everyday work, rahter than the findings that may be useful only occasionally or rarely. It is not in any sense a "standard ", however; nor is it so elementary or so conclusive as to provide a "rule of thumb" for non-en gineers. It is the purpose of this section to provide a basis for the structural design of self-supporting steel transmission towers prevailing practice and many laws call for towers to be designed i accordance with the requirements of the current edition of the National Electrical Safety Code (NESC). This code was written primarily to cover the electrical features of transmission lines, and not features of structural design. It was also written primarily to provide ru les for safety and clearances, without the intent to restrict the structural de signer by imposing design formulas and considerations on him, but rather to afford him a freedom of choice in preparing a tower design. This leaves the determination of design criteria to the discretion of the designer and as a re sult, there has been a wide variance in the criteria used in the design of to wers. This section has been prepared to provide more specific loading recom mendations for transmission towers. Other features include design formu las for use in structural analysis, fabrication and testing recommendations, foundation nomenclature, survey information and construction methods. The recommendations reflect the experience of good practice and actual tests conducted on many transmission structures. It provides guide lines that may be used by any individual company in establishing specifications for transmission-line structures. This section also cover loadings, overload factors, compression formulas, slenderness ratios, detailing and fabrication, fasteners, fullscale tests, sur veys, foundations, and construction for self-supporting steel transmission towers. One of the many ways in which tower design differs from bridge and buil ding design is that tower design uses overload factors to incorporate factors of safety in place of reducing the allowable stress. In tower design, the basic loads in increased by the use of an overload factor and the tower is designed to stresses approaching failures in yielding and buckling. In building and bridge design, the actual loads are used and the structure is designed to stresses at specified percentages of the failure in yielding or buckling. The overload factor approach to design allows the variation of each item of strength (vertical, transverse, and longitudinal), to be controlled according to its importance in the structure. In this section, loadings took place In detail and were classified as follows: a) Climatic loads which are related to the reliability requirements, b) Failure containment loads which are related to the security require mats and c) Construction and maintenance loads which are related to safety requirements. İt is possible to give in detail requirements for each of the three loading categories in this chapter which is divided into five each one dealing with the following loading items requirements: wind loads, ice without wind, ice with wind, loads for construction and maintenance and loads for failure contain ment. Afterwords, wind direction and extreme wind loads for overhead power- line design were studied. In the crrent design calculations of wind loads for overhead transmission and distribution lines, the annual extreme wind is al ways assumed to act normal to the line. While it is safe to assume that the wind acts normal to the line, this assumption may result in overdesign. In ot her words, it may lead to the underestimation of the line reliability. İn this paper a method is described to calculate design wind loads taking into consi deration the wind direction and line orientation. Hereafter the annual extre me wind speeds and loads which do not consider the direction effect will be called non-dii'ectional annual extreme wind speeds and loads and those which account for the direction effect will be termed directional annual ext reme wind speeds and loads. The method mentioned was applied in Toronto and London. The results and findings of researchs can be summarized in the following charts. VII 1 I i Kİ \İ -Yi '.iz âl I ga Et>% N S NWE-SfV ME-&VK lue-uiSYV E-W £St-w:*V SE-»«W 5SE-NWW Line orientation Decrease in Annual Extreme Mean Wind Speed Decrease in Annual Extreme Wind Load Increase in Span Length Fig. 3.10 Change in annual extreme wind speed, wind load and span length for different line orientations (Toronto, Ontario) N-S fWf 'S5W NE-JW ENg-WS*' f-W EHt-VJSW 5t-«* SS£ »»»*> Line orientation y /\ Decrease in Annual Extreme Mean Wind Speed IVsl Decrease in Annual Extreme Wind Load Vs/A Increase in Span Length Fig. 3.11 Change in annual extreme wind speed, wind load and span length for different line orientations (London, Ontario) VII 1 In the chapter of the surveys on transmission lines design, a study with computer was also mentioned. In the study of the design of transmission tower selection and spotting on a given ground profile has been computer ized. In particular programs have been written that compute and plot the ground profile and also determine unallowable regions for tower spotting. The optimal tower selection and spotting is accomplished using dynamic pro gramming method. The programs have been successfully applied to the 154 kV Kartal-Adapazan transmission project. An important problem of transmission line design is the tower position ing problem. This problem can be separated into 3 parts: 1- To determine the top view route through which the transmission line passes. 2- To obtain the profile of the selected route. 3- To find the types, heights and positions of the towers to be erected along this profile. The plotting program consists of the subroutines below: a- Subroutine Step 1: calculates the coordinates of open travers points and auxiliary open travers points, b- Subroutine Step 2: Calculates the unallowable regions for tower positioning, c- Subroutine Step 3: Calculates the coordinates of detail points on centre-line (profile), d- Subroutine Step 4: Calculates the coordinates of points on side hill, e- Subroutine Step 5: Finds the coordinates of points which are « didate for tower positioning, f- Subroutine Step 6: Draws the profile and modified side-hill. Before the description of these subroutines, the calculation of coordinates of a point with respect to a reference point is briefly reviewed. In the section "reliability based design of transmissions lines according to recent advances by IEC and CIGRE", the works of two international estab lishments were informed. This paper gives the background and the methodology that led to the load and strength factors appering in some documents of the two working groups. Many important questions are discussed in the paper such as: - Relation between load and strength that lead to a consistent reliabi lity. IX - Effect of span dispersion on reliability and methods of incorporating this effect in the design of towers. Effect of the number of components subjected to the maximum intensity of climatic loads. - Strength factors that lead to a preferred sequence of failure. Section 5 discussed probabilistic methods which are of practical interest for the reliability evaluation of engineering systems and to present computer experiments with some of these methods. The results are useful for calculat ing the reliability of different types of systems with uncertain interdepen dent properties and acted on by random interdependent loads, including both structures for supporting overhead electric transmission lines and un derground distribution systems. And after that presented a universal tool for calculating the reliability of any transmission line component when random conditions of wind velocity, wind direction, ice thickness, temperature, drag coefficient and component strength are specified. The calculation process uses state-of-the-art tech niques of probability theory and is implemented in a computer program named DESCAL. In the section 6 probabilistic optimization of transmission line design was discussed. As it is known the optimum design of a transmission line is very sensitive to future load growth and economic variables. Once these variables have been chosen, an optimization program is very useful for determining the most economical conductor size, steel-to-aluminum ratio, span length and tower heights. However, because of the uncertainties in load growth and economic variables, it is difficult to choose the conductor and corresponding hardware, insulators and towers that would optimally halance capital costs with the cost of losses over a 50 year life of the line.