Pdf a method for the sagtension calculation in electrical. The procedure for finding the initial sag and tension in. Sag and tension chart for multiplex conductors multiplex. These tension limits specify certain percentages of the conductors rated breaking strength that are not to be exceeded upon installation or during the life of the line.
External companies should not use these standards to construct nonergon energy assets. In this example we will calculate the sag and tension if the conductor supports are at different elevation. Utility line design has over twentyfive planned calculations that will be added to the website at no added charge in the coming months. The graphic method for sagtension calculations is a system. The tension to sag option allows a user to input the initial stringing tension, and have. Sag calculation for supports are at equal levels suppose, aob is the conductor. Sagtension calculations a tutorial developed for the ieee tpc line design subcommittee. Similar to the symmetrical r od distribution, the tension insulators shows a deflection about 10cm. As is usually the case, the contribution of belt stiffness in limiting belt sag is small in relation to belt tension. Finally, an output format and mode can be selected.
Calculation of sag and tension in transmission line depend on the span of the conductor. The following formula for the sag in a parabola can be used for level. Abstractthe ruling span concept is widely used to calculate sags and tensions for new overhead transmission lines and for up grading existing lines. Normally the tension in conductor is kept one half of the ultimate tensile strength of the conductor and therefore safety factor for the. Therefore, in actual practice, a compromise is made between the two. A tensioning section of a power line consist of six spans with the length 350, 200, 450, 500 and 325 meters. If a conductor is sagged with a given tensile force between points a and b representing the attachments of the conductor at the supports, a curve, the sagging curve or catenary figure 14. Belt conveyors for bulk materials practical calculations metric and us systems jurandir primo, pe 2009. If we run a sag tension program for each of the diff erent span lengths using the initial tensions from the above ruling span printout, we would fi nd that spans shorter than the ruling span have less sag and higher tension than the ruling span and spans longer than the ruling have greater sag and less tension than the ruling span.
Ab w is the weight per unit length of the conductor t is the tension in the conductor. These factors enable the program to calculate regular sags and tensions of ruling spans, in addition to providing users with access to new output on structural. Sag and tension calculation free download as excel spreadsheet. The sag of an overhead line is directly proportional to the weight of the conductor. The guidelines for preparing or selecting sagtension. Calculations of maximum sag of a transmission line. Pdf sagtension calculations a tutorial developed for. Calculations of maximum sag of a transmission line with an.
Sag and tension of transmission and distribution lines. This paper presents a method for the sag tension calculation of. Most sag tension programs do not model this effect and thus underestimate the sags. The linemans pocket reference conductor tension calculator. Sagtension calculation methods for overhead lines ecigre.
The horizontal component of tension remains constant throughout the span of conductor. Belt conveyors for bulk materials practical calculations. For a small span up to 300 meters parabolic method and large span like river crossings catenary method is used for the calculation of sag and tension. Creep is not considered as a factor in final sag in this calculation. The sag to tension option allows a user to enter a measured sag value, to calculate a spans tension. Span having equal level supports is called level span, whereas when the level of the supports is not at an equal level is known as unequal level span. Sag calculation in overhead line sag in overhead line. Too little tension and the sag of the line can be excessive. Tension calculations valid for any line geometry brian mcdonald. Plscadd can model your line both with and without the compression effect so you can see how severe it is. 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. The document is organized by first describing the underlying.
The overhead transmission line conductors sagtension calculations are. In the previous post, we calculated the sag and tension of a transmission line given that the conductors supports are at the same elevation. In an overhead line, the sag should be so adjusted that tension in the conductors is within safe limits. An electric power line of length 140 m and mass per unit length of 3 kgm is to be suspended between two towers 120 m apart and of the same height. Sag in overhead transmission line and its calculation. Tension force physics problems, two ropes or cables on hanging mass with angles, static equilibrium duration. These standards ensure meeting of ergon energys requirements. The sag equation dx, which is usable for the sag calculation at any point of. Span having equal level supports is called level span, whereas when. The vertical distance of the conductor to the line connecting both attachment points a and b is called the.
The conductors connected between the tower structures must not be connected too tight or too loose. It is also assumed the conductor length does not change with changes in temperature or stress. The sag and tension values of overhead conductors are influenced by the creep developed during the line lifetime. It is critical that utility personnel apply the appropriate tension to overhead conductors. Calculations of sag and tension in transmission line depend on the span of the conductor. Fernandez1 abstract the sag and tension values of overhead conductors are influenced by the creep developed during the line lifetime. Engineering aerial facilities ota technical conference september 4, 2014. Determine the sag and maximum tension in the power line.
The tension is generally decided by many factors like wind speed, ice loading, temperature variations etc. Sample calculation of sag and tension in transmission line uneven elevation posted by admin in the previous post, we calculated the sag and tension of a transmission line given that the conductors supports are at the same elevation. Stepbystep sag and tension computation using ruling span. Fernandez 1 abstract the sag and tension values of overhead conductors are influenced by. The calculation of conductor at an equal level shown below. A method for the sagtension calculation in electrical. Abstract this paper presents new equations for conductor height calculation based on the known maximal sag. A novel affine arithmetic aa based transmission line sag, tension and conductor length calculation for parabolic curve is proposed and the proposed method is tested for different test cases. As discussed earlier in this post, enough sag shall be provided in overhead transmission line to keep the tension within the safe limit.
Southwire has improved the calculation algorithms to reduce the occurrence of these failures. A method for the sag tension calculation in electrical overhead lines i. During the erection of overhead transmission line, the conductors are connected between two tower structures. The sag in overhead line is a length in between support point of conductor and the lowest point on the conductor of. Too much tension and the conductor can snap in cold weather.
By refining the input used in this equation, and augmenting. Pdf sag and tension of conductor sead saric academia. Jacques hamian and yair berenstein abstract sag tension programs have traditionally calculated the conductors sag tension characteristics using the alcoa graphic method. Conductor weight sag of the conductor is directly proportional to its weight. Examples are included that provide comparisons to traditional analysis methods. Sample calculation of sag and tension in transmission line. You will know how to calculate sag and sag formula. Sag and tension calculation strength of materials electrical. This paper presents a method for the sagtension calculation of overhead conductors that is characterised by the creep sequential calculation. As designers push conductors further out in the loading curves, root failures during the sag tension calculation can become a problem. It is because low sag means a tight wire and high tension, whereas a low tension means a loose wire and increased sag. Standard for distribution line design overhead these standards created and made available are for the construction of ergon energy infrastructure.
A pdf or a csv file can be generated, and the mode can be either sag to tension, or tension to sag. The shape of sag increases with the increase in the length of the span. We generally see a lot of overhead lines on our way. The effects of ruling span on sag and tension iaei magazine. Sag tension calculation methods for overhead lines. Because, low sag means a tight wire and high tension, whereas low tension means a loose wire and increased sag. Let, l length of the span, w weight per unit length of the conductor, t tension in the conductor. Pdf the sag and tension values of overhead conductors are influenced by the creep developed during the line lifetime. The minimum tension to prevent belt sag between two rolls, t s is. The equations needed to calculate ruling spans and conductor sags and tensions. The following calculations are included in the website, requires minimal training and take seconds to perform.
Catenary curve, calculation of sag tension, effect of. Sag in general words can be said that distance between the highest point of electric poles or towers and the lowest point of a conductor connected between two poles or towers. Most conductor sag and tension calculations are theoretically based on a simple deadend span of conductor supported at equal elevations. This is because the weight of any body acts vertically downwards.
Abstract the sag and tension values of overhead conductors are influenced by the creep developed during the line lifetime. Like most line design programs, plscadd uses ruling span approximations in its sag tension calculations. Alcoa graphic method for sag and tension calculations for acsr and other conductors sag and tension with creep elevated temperature creep inclined span calculation stringing sag calculation graphic output of galloping ellipses and sag curves offset clipping calculation. Refinements and enhancements made by trimble energy solutions by. Southwires sag10 software combines more than 90 years of sagtension calculating experience with over 65 years of conductor design and modeling expertise to. Overhead transmission line sag estimation using a simple. A new version of southwires sag10 software for calculating sag and tension in overhead conductors is now available with. In order to find the maximum tension is necessary to calculate the effective tension, that is, the force. Parabola and catenary equations for conductor height calculation alen hatibovic. The conductor 304al149st1a acsr 30050 is installed with initial horizontal tension of 17685 n at 10 o c. Module 7 1 calculate tension in a rope given sag youtube. The equations can be directly applied for plotting the conductor curve after a completed sag tension calculation for planning and designing overhead lines.
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