Overhead line design considerations for conductor creep. Calculate the sag of conductors using matlab file exchange. Take note that because of the complexity of the creep in a conductor, it is not a factor in these calculations. Pls caddultralite is a streamlined version of plscadd for quick modeling of a single span of conductor or wire. There are many factors associated with determining sag including stringing tension, ambient temperature, average temperature of the coldest month in the line location, surrounding terrain, etc. The cable in a single span of a transmission line can be described by a set of hyperbolic functions which describe catenary curves 1. Transmission line loading 3 in any overhead transmission line, there will be multiple support structures. Apr 17, 2018 sag is defined as the different in level between points of supports and the lowest point on the conductor. Similarly, if the sag is low, then when the line contracts in the winter, low sag will indicate a high tension, and as a result of this contraction, the line may snap. These standards ensure meeting of ergon energys requirements. External companies should not use these standards to construct nonergon energy assets. In this article, the generic term overhead line is used, as used by the international union of railways. Excessive sag, on the other hand, requires more raw material.
How to determine the sag in transmission lines sciencing. Utility line design has over twentyfive planned calculations that will be added to the website at no added charge in the coming months. Standard for distribution line design overhead these standards created and made available are for the construction of ergon energy infrastructure. In addition, the permanent mechanical forces everyday stress elongate. A free, internet licensed, version of plscaddultralite is available for download. May 23, 2017 similarly, if the sag is low, then when the line contracts in the winter, low sag will indicate a high tension, and as a result of this contraction, the line may snap. The calculation of conductor at an equal level shown below. A heavy ice storm may occur the day after the line is built or may never occur over the life of the line. Conductor weight sag of the conductor is directly proportional to its weight. The live script presents calculations of the sag for power lines. 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. Overhead transmission line sag estimation using a simple. Download rulingspansaglite and enjoy it on your iphone, ipad, and ipod. Sagtension calculation program for wood pole overhead lines.
Feb 06, 20 the reason for this unpredictability is that the occurrence of heavy ice and wind is random. The tightness of the wire can be input as horizontal tension, catenary, sag, or slack. As shown in the figure above, a transmission line is supported at two points a and b of two different transmission towers. As promised, you can download for free my sag tension spreadsheet calculator. This bulletin presents the methodology and equations required to calculate distribution line ruling spans and conductor sags and tensions. Using this methodology, conventional programs calculate the conductors sagtension characteristics. The sag equation dx, which is usable for the sag calculation at any point of.
It is the proportional ratio of the temperature and depth of sag. The energized conductors of transmission and distribution lines must be placed to totally calculation of overhead line sags. A method for the sagtension calculation in electrical. April 2016 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. Cable length calculator from sag, span find conductor length.
Wo2008097458a1 powerline sag calculation by way of power. Sag in overhead transmission line and its calculation. Cable length in any transmission line between two point will always be larger than the original length between the two points as there will be certain sag involved. 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. A sag calculator 122 computes sag for a span of a section of a power line based at least in part upon a temperature of. Sag depends on tower distance, wire weight and tension.
The ruling span concept is widely used to calculate sags and tensions for new overhead transmission lines and for upgrading existing lines. Sag10 software, a play on words for sag ten tension, is widely recognized as the industry standard for overhead conductor sag tension calculations, utilizing the alcoa graphic method. It is assumed that points a and b are at the same level from the ground. A method for the sagtension calculation in electrical overhead lines i. Fernandez 1 abstract the sag and tension values of overhead conductors are influenced by. It provides satisfactory results for a level line with relatively uniform spans at any temperature, or for any span length of a level line at low temperature. It develops a sagtension report as well as stringing charts for a user definable range of span lengths and stringing temperatures. The sag of a transmission line will increase by increasing conductor temperature caused by the electrical load and spec ific environmental conditions or additional rope forces e. 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. Utilities are continuously investigating methods to economically reinforce their overhead line ohl networks by reconductoring with larger conductors or with novel hightemperature low sag htls conductor technologies. The distance between any two structures is called a span.
Dec 07, 2018 sag in overhead transmission line conductor refers to the difference in level between the point of support and the lowest point on the conductor. Another program that is used for the calculation of the parameters of overhead lines is the program line constants from atpemtp. Sag is defined as the different in level between points of supports and the lowest point on the conductor. If the sag is large, and the line becomes heavily loaded, then the sag will further increase and breach the safety clearances. Bulletin 1724e152 page 3 the mechanics of overhead distribution line conductors 1. Handle multiple overhead line spans between deadend structures.
Ab is the horizontal line and from this horizontal line to point o, s is the sag when measured vertically. The author begins with an analysis of the many and varied mechanical forces that overhead power line towers are required to withstand. Guide to the installation of overhead transmission line conductors, is to provide guidance for an optimized installation of overhead conductors. To further optimize the ohl design, conductor creep. Index termsampacity, bare conductors, conductor creep, overhead line, reconductoring, retensioning, sag, thermal rating. Pdf sagtension calculation program for wood pole overhead. You can use this spreadsheet to verify the results in my sample computation in the previous post.
The overhead line sag dependence on weather parameters and line parameters are overhead line sag, sag and tension of transmission and distribution safety. A method for the sag tension calculation in electrical overhead lines i. Sagtension calculations a tutorial developed for the ieee tpc line design subcommittee. The transmission line tool on mobile tltm ruling span sag. The shape of sag increases with the increase in the length of the span. The recommended dimensions for the stringing sheaves and bullwheel tensioner have been adapted. Calculating sag for distribution lines cr4 discussion thread. Calculations of maximum sag of a transmission line with an. Catenary calculations and sag tension analysis tools enable users to design, edit and optimize transmission lines accordingly. Line tension varies with temperature with maximum tension and minimum sag occurring at the coldest temperature and viceversa. Southwires sag10 software combines more than 90 years of sag tension calculating experience with over 65 years of conductor. It explains the guidelines used for preparing or selecting sagtension tables.
The graphic method for sagtension calculations is a system. Transmission and distribution conductor tension in overhead. If you would like to work with our high voltage overhead line calculation programme, you can download it free. Sagtension calculation methods for overhead lines ecigre. Overhead conductor installation guide general cable. As cable are not stiff object, its natural they have a parabolic shape. The overhead line sag dependence on weather parameters and. Sagging transmission lines are actually a feature of highvoltage wires, because the towers are too far apart to allow sufficient tension to keep the lines parallel to the ground. The overhead line sag dependence on weather parameters and line current elisabeth lindberg as the demand for energy increases, as well as the demand for renewable energy, vattenfall, as network owner, receives many requests to connect new wind power to the grid. Discrepancy between installed line tensions and the tension used for calculation leads to errors which touch on almost every facet of line design, including. An overhead line is designed on the principle of one or more overhead wires or rails, particularly in tunnels situated over rail tracks, raised to a high electrical potential by connection.
If the sag is too large, it may cause a short circuit between the line and objects below it or a short circuit between lines in extremely windy conditions. Electra complies with en 50423321 and en 504231 standards. Find existing calculation procedures and methods in literature. The limiting factor for how much wind power that can be connected to the. Volume 6 part 2 takes the reader through the philosophy, theory, principles and practices of the design and fabrication of overhead power line structures. The men engaged in the erection of overhead electric power transmission lines should be provided with tables or charts giving the sag or tension at different. Pdf a method for the sagtension calculation in electrical. Full text of graphical determination of sags and stresses. Electra includes build in cables library and load parameters which can be user defined and customized. Sagtension spreadsheet free calculator even elevation. Introduction he need to increase the power transfer capacity of existing distribution and transmission lines has resulted from the growth in demand for, and generation patterns of, electrical power. Sag10 software, a play on words for sagten tension, is widely recognized as the industry standard for overhead conductor sagtension calculations, utilizing the alcoa. The overhead transmission line conductors sagtension calculations are typically based on the catenary equation, which describes an entirely. Rowland, senior member, ieee, and boud boumecid abstractthe rating current ampacity of a conductor erected on a particular overhead line ohl structure installed at a speci.