Sag And Tension Of Conductor Pdf

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This is an example calculation for sag and tension in transmission line. You may opt to review first the fundamental principles and formulas from the previous post. Creep is not considered as a factor in final sag in this calculation.

Sag in Overhead Transmission Line and Its Calculation

Convenor of WG B2. Douglass United States M. Gaudry France D. Douglass United States S. Hoffmann United Kingdom. Argasinska Poland , K. Hodgkinson Australia , S. Hoffmann United Kingdom , J. Iglesias Diaz Spain , F. Jakl Slovenia , D. Lee Korea , T. Massaro Italy , A. Maxwell Sweden ,G. Mirosevic Croatia , D. Muftic South Africa , Y. Ojala Finland , R. Puffer Germany , J. Reding United States , B. Risse Belgium , T. Seppa United States , R. Stephen South Africa , S.

Ueda Brazil , L. Motlis Canada, deceased , V. Rawlins United States , D. Havard Canada , K. Papailiou Switzerland WG B2. Brennan Australia , J. Riisio Finland , E. Ghannoum Canada , C. Hardy Canada , P. Copyright Ownership of a CIGRE publication, whether in paper form or on electronic support only infers right of use for personal purposes. Are prohibited, except if explicitly agreed by CIGRE, total or partial reproduction of the publication for use other than personal and transfer to a third party; hence circulation on any intranet or other company network is forbidden.

Disclaimer notice CIGRE gives no warranty or assurance about the contents of this publication, nor does it accept any responsibility, as to the accuracy or exhaustiveness of the information. All implied warranties and conditions are excluded to the maximum extent permitted by law.

Table of Contents List of Figures Figure 29 - Sag-tension calculations of maximum, loaded conductor tension illustrating the effect of plastic elongation All conductors have an aluminium strand area of mm2.

The various mathematical tools and conductor data considered herein are used to predict sag and tension of catenaries at the full range of conductor temperatures and ice and wind loads that occur over the rather long life of an overhead power line. The goal of the document is not to develop a unique or best calculation method, but to describe the overall process and explain the common calculation methods.

Introduction Historically, for most overhead transmission lines, the sag of conductors or tension is measured at the time of construction when the line is not energized. Once the line is constructed, the phase conductors may be subject to high temperatures during periods of high electrical loading and both the lightning shield wires and phase conductors must remain intact during high ice and wind load events for an expected useful life of 40 years or more.

Under all foreseeable conditions, the conductors must not break under high tension, fatigue under persistent wind-induced motions, nor sag such that minimum electrical clearances are compromised. Span Length. To assure that these conditions are met over the life of the line, the engineer must specify initial measured i. Sags and tensions for all foreseen temperatures, over the life of the line, including those above 50oC which may result from high electrical current loads See sag at maximum electrical load in Figure 1.

The maximum conductor tension under ice and wind loads which strain structures i. Conductor tensions during the coldest periods of winter to allow for sufficient self-damping to prevent aeolian vibration-induced fatigue over the life of the line.

The Catenary Equation The catenary equations both exact and approximate are examined for both level and inclined spans. The various relationships between sag, tension horizontal and total , weight per unit length, and span length are studied and explained.

The concept of slack difference in length between conductor and span is defined and an important discussion of limits on calculation accuracy is included. Both approximate parabolic equations and the exact hyperbolic catenary equations are explained.

The catenary constant tension divided by weight per unit length is shown to be an essential parameter of these equations. Figure 2 shows a typical relationship between sag, conductor tension, and slack, calculated with the catenary equation. As explained in the brochure, an increase in any or all of the components of conductor elongation e. Mechanical Coupling of Spans Transmission lines are usually comprised of multiple line sections. Each line section is terminated at each end by a strain structure that allows no longitudinal movement of the conductor attachment points and that the terminating insulator strings experience the full tension of the conductors.

Tangent suspension structures are used within the line section to support the conductors. At suspension structures, the insulators and hardware used to support the conductors are usually free to move both transversely and longitudinally to the line and any modest difference in conductor tension between adjacent spans is equalized by small movements of the bottom of the insulator strings. This tension equalization between suspension spans works reasonably well for modest changes in conductor temperature and small differences in ice and wind loading.

The brochure explains how this simplifies the sagging of conductor during construction and stringing and in simplifying sag-tension calculations with the assumption of a ruling or equivalent span. The discussion of slack, and the sensitivity of tension and sag to it, is applied to demonstrate how tension equalization at suspension supports occurs and under what conditions errors in calculation become significant. The physical understanding of the ruling span concept, as described in the brochure, is helpful in identifying those line design situations where it should not be used.

Conductor Tension Limits Sag-tension calculations are normally performed with multiple constraints on tension and sag. The brochure describes the purpose of various tension limits and recommends references that provide guidance in setting specific values. Conductor Elongation Elastic, Plastic, and Thermal The most important differences in sag-tension calculation methods involve the modeling of conductor elongation due to changes in tension, temperature and time.

In the simplest elongation model Linear Elongation , plastic elongation is ignored, and conductor elongation under tension is assumed elastic. In a somewhat more sophisticated model Simplified Plastic Elongation , plastic elongation is represented by a typical value based on experience.

In the most accurate conductor elongation model Experimental Plastic Elongation , plastic elongation is calculated based upon experimental laboratory conductor test data. Figure 3 - Conductor elongation diagram. Sag-tension Calculation Methods The brochure acknowledges the widespread use of numerical solutions to sag-tension calculations but uses graphical representations to provide the reader with insight concerning the advantages and limitations of calculation methods of varying complexity.

In this section, typical sag-tension calculation results are discussed. The usual meaning of initial and final conditions is explained and their calculation demonstrated for the different conductor elongation models.

The interaction of the steel core and aluminum layers under high tension and high temperature conditions is demonstrated graphically. Parameter Sensitivity In the final section of the brochure, some insight is provided into the influence of various key parameters used in sag-tension calculations. For example, variation in the thermal elongation coefficient of a stranded aluminum conductor can have considerable influence on the sags calculated for a line at high conductor temperatures.

As shown in Figure 4, the sag at oC 9. Thermal Expansion CTE Figure 4 - Influence of variation in the coefficient of thermal elongation on high temperature sag. It is clear from the discussion that, even with very careful laboratory tests and modern calculation methods, sag calculation errors cannot be less than to mm and are generally considerably greater.

Conclusions The sag-tension calculation process, with both exact and approximate catenary equations, is described in some detail. Three conductor elongation models are defined and the more complex, experimentally based model is recommended because its use allows the line designer to estimate both high temperature sags and maximum structure tension loads with superior accuracy.

Given the prevalence of numerical calculation tools, there is little need to use the approximate catenary equations or the simplified elastic conductor elongation models but the ruling span assumption of tension equalization between spans appears to be sufficiently accurate to be used in many new line designs. Regardless of the calculation technique and conductor elongation model selected, it is concluded that there continues to be a need for sufficient clearance buffers in the design of new lines and the uprating of existing lines because of uncertainties in modeling the load sequence and detailed mechanical behavior of bare stranded overhead conductors.

ABSTRACT This brochure identifies and describes the most essential elements of the sag-tension calculation process and the various mathematical and experimental methods used to predict sag and tension of catenaries over the whole range of conductor temperatures and ice and wind loads that may occur over the life of a line.

The goal is not to develop a unique calculation method, but to explain the overall process and identify the alternative modeling methods that are available.

The engineer is provided with a basic explanation of the sag-tension calculation methods that are in common use throughout the world and with a physical understanding of the processes and mathematical relationships that underlie these methods. Ampacity - The maximum constant line current which will satisfy the design, security and safety criteria of a particular line on which the conductor is installed. In this brochure, ampacity has the same meaning as steady-state thermal rating. Annealing - The process wherein the tensile strength of copper or aluminium wires is reduced at sustained high temperatures, usually above 75oC and 90oC respectively.

EDS Everyday Stress The tension or stress that a conductor normally experiences for most of its service life, typically at a conductor temperature of 0oC to 25oC without wind or ice. Electrical Clearance - The distance between energized conductors and other objects such as conductors, structures, buildings, and earth.

Minimum clearances are usually specified by regulations. Elongation, Elastic Bare overhead conductors elongate under tension, increasing in length with increasing tension and decreasing in length with decreasing tension. Elastic elongation of conductor is spring-like.

The conductor returns to its original length unloaded length when tension is removed. Elongation, Plastic Aluminum strands and, to a much lesser extent, steel strands, used in bare overhead conductors, undergo plastic i. Initial plastic conductor elongation includes strand settlement and deformation which occurs during stringing and sagging Initial Plastic Elongation , plastic elongation which occurs during relatively brief, high tensile-load events, and long-time metallurgical creep elongation which occurs at everyday tension levels over the life of the line.

Metallurgical creep of aluminum is accelerated at sustained high temperatures above 20oC. The components of plastic elongation are not additive e.

Sag Chart For Acsr Conductor - Sag And Tension Claculation

The maximum dip sag is represented by the value of y at either of support A and B. Length of span m Weight per unit length of conductor kg Tension in the conductor kg different in levels between two supports Distance of support at higher level Distance of support at lower level. Pole Span S1 m S2 m 40 40 45 45 50 50 55 55 60 60 65 65 70 70 75 75 80 80 85 85 90 90 95 95 Open navigation menu. Close suggestions Search Search. User Settings.

Sag in overhead Transmission line conductor refers to the difference in level between the point of support and the lowest point on the conductor. Sag in Transmission line is very important. While erecting an overhead Transmission Line, it should be taken care that conductors are under safe tension. If the conductors are too much stretched between two points of different Towers to save conductor material, then it may happen so that the tension is conductor reaches unsafe value which will result conductor to break. Therefore, in order to have safe tension in the conductor, they are not fully stretched rather a sufficient dip or Sag is provided.

Request PDF | On May 16, , Dale Douglass and others published Sag and Tension of Conductor | Find, read and cite all the research you.

Transmission Line Design (Sag & Tension Calculation) in eastern Grid Project

Convenor of WG B2. Douglass United States M. Gaudry France D.

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Transmission Line Design (Sag & Tension Calculation) in eastern Grid Project

Report Download. Theseconditions, along with the elastic and permanent elongation properties of the conductor, providethe basis for determinating the amount of resulting sag during installation and long-term operationof the line. Accurately determined initial sag limits are essential in the line design process. Final sags and tensionsdepend on initial installed sags and tensions and on proper handling during installation. The nalsag shape of conductors is used to select support point heights and span lengths so that the minimumclearances will be maintained over the life of the line.

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PDF | The sag and tension values of overhead conductors are influenced by the creep developed allow the calculation of the conductor sag and tension for.


In this example we will calculate the sag and tension if the conductor supports are at different elevation. Creep is not considered as a factor in final sag in this calculation. Also, loading of the conductors are based on the National Electrical Safety Code A transmission line conductor was strung between two towers Structure 1 and 2 , meters apart and different elevation as shown in the figure above. Line 3 is 12 meters above the ground and the distance between phases is 3 meters.

Энсей Танкадо только что превратил ТРАНСТЕКСТ в устаревшую рухлядь. ГЛАВА 6 Хотя Энсей Танкадо еще не родился, когда шла Вторая мировая война, он тщательно изучал все, что было о ней написано, - особенно о кульминации войны, атомном взрыве, в огне которого сгорело сто тысяч его соотечественников.

Не коснувшись краев, он вытащил из нее ключ Медеко. - Поразительно, - пробурчал он, - что сотрудникам лаборатории систем безопасности ничего об этом не известно. ГЛАВА 47 - Шифр ценой в миллиард долларов? - усмехнулась Мидж, столкнувшись с Бринкерхоффом в коридоре.  - Ничего .

 М-м… сто десять фунтов, - сказала Соши. - Сто десять? - оживился Джабба.  - Сколько будет сто десять минус тридцать пять и две десятых.

Sample Calculation of Sag and Tension of Transmission Line – Even Elevation

 - Мы говорим о математике, а не об истории. Головы повернулись к спутниковому экрану.

Мы не можем вычесть их все одно из другого. - Многие пункты даны не в числовой форме, - подбодрила людей Сьюзан.  - Их мы можем проигнорировать. Уран природный элемент, плутоний - искусственный.

Мою колонку перепечатывают издания по всему миру. - Сэр! - Беккер поднял обе руки, точно признавая свое поражение.  - Меня не интересует ваша колонка. Я из канадского консульства.

Sample Calculation of Sag and Tension in Transmission Line – Uneven Elevation