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Generating Ruling Span Sag-Tension Runs in PLS-CADD/Lite

PLS-CADD/Lite Screen Shot - Click to See Enlarged View

This TechNote describes how to use PLS-CADD/Lite to make stand-alone sag-tension runs. Please keep in mind that this practice is redundant as the same sag-tension routines can be used interactively in PLS-CADD to calculate sag-tension data, make required checks (such as galloping, tension limits, etc.) and produce stringing charts. However, many transmission engineers still need to create sag-tension charts, so here is how to do it.

  1. Start by opening PLS-CADD.
  2. Select File/New, and then choose the PLS-CADD/Lite menu item.
  3. You will be presented with the option to specify a folder and name of your PLS-CADD/Lite project (which should have a ".loa" extension - LOA stands for "loads" and indicates this is a PLS-CADD/Lite project).
  4. You will then see a dialog box for the wizard function.
  5. You will now be taken to the Model Setup screen, where PLS-CADD/Lite has started you off with basic information for setting up four 250' spans ahead and four 250' spans back of Drake conductor, based on a 250' ruling span. You can modify all eight rows, delete entire rows, or even add rows depending on how many sag-tension runs you want and if you need any sag coordination, phase-to-phase clearances, or galloping checks. Simply change this default information by:
  6. You will now see the screen refresh with your wires shown on the left hand side in the profile view and on the right hand side in a 3d view. All of the PLS-CADD functions such as zooming and rotating are available should you want to see these views in different perspectives.
  7. To generate a sag-tension report, simply select Sections/Sag-Tension and then click on the Next button until the desired section is selected. Then click on the report button and you will be presented with a full sag-tension report ready for printing or copying into another program such as Word or Excel.

That is all it takes to create a sag-tension report. Of course there are quite a few other options in PLS-CADD/Lite that you might want to take advantage of such as:

To make any changes to your model, simply go back into Line/Setup and make whatever modifications you need to.

Don't forget that if you first model your structure in PLS-POLE or TOWER, you can check the Use Existing Structure File option and then you will not need to input the Origin XYZ values (since they will come from the structure file). Once you OK out of this table, the geometry view is updated and you can use the Structures/Check menu item to check your PLS-POLE or TOWER structure. You will receive results in both reports and graphics views that will show you if you had any failures, where those failures occurred and how much stress was applied to each part of the structure (and insulator) for each load case. You can even click on the Structures/Generate Allowable Spans menu item and PLS-CADD/Lite will report the maximum wind and weight spans that your structure is good for given the current set of loading conditions and parameters.

Additionally, PLS-CADD/Lite allows you to string up to 60 cables with any relationship to each other and then to perform cable to cable clearance checks under varying conditions. So if you've got that ADSS cable that your cable supplier is just telling you to string up at "1% sag" and you are concerned about the clearances when your conductors are operating at high temperatures you can model both of them and check it! Better to do it now than to end up with wrapping problems in the field later.

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