Q261 : Subdivision in SESCAD

Question
When running MALZ, I get a message about short conductors in the network that "violate the thin wire assumption". On the other hand, when I use SESCAD's diagnostic tool, it doesn't report any short conductors. Why is that?


Answer
Presently, SESCAD and the engineering modules use different approaches to carry out conductor subdivision. The main reason for this is that SESCAD requires algorithms that detect conductor intersections in several contexts (such as Auto-Snap, Power Tools, etc...). The engineering programs are optimized to carry out subdivision for the entire network; the algorithms they use are very difficult to adapt for the more interactive and context-sensitive tasks in SESCAD. Therefore, an independent algorithm was developed for Auto-Snap in SESCAD. To maintain internal consistency, this same algorithm has to be used when subdividing the entire network. This results in some discrepancies. For instance, SESCAD generally doesn't generate very short conductors when subdividing since this would violate the Auto-Snap condition. Other differences come from the fact that SESCAD does not (yet) take into account the soil model and the user-specified conductor subdivision number when subdividing.

To get rid of the problems caused by those short conductors, one possibility is to leave the short conductors in and adjust the engineering program's tolerances so that it accepts them. If there aren't many short conductors, this should not affect the computation accuracy significantly. To change the tolerance, go to the System / Advanced screen in MALZ or HIFREQ and enter a very small value for the Thin-Wire Approximation Ratio. In MALT, this parameter can be accessed by clicking the Advanced button on the main screen.

If you would prefer to remove the short conductors (perhaps because there are so many of them that it could affect the computation accuracy or increase the run-time), you can still proceed as above and run the engineering software once with all the short conductors. Once the run is complete, the program produces a file that lists the conductor segments after subdivision and that can be imported in SESCAD. The file is called mt_JobID.F07, mz_JobID.f17 or hi_JobID.f17 for MALT, MALZ and HIFREQ, respectively. Those files only contain the conductor information; to preserve the complete data of your input file, you should:

1. Open your original input file in SESCAD
2. Delete all conductors.
3. Import (File / Import) the corresponding F17 (or F07) file.

At that point, you can use SESCAD's diagnostic tools to clean-up the network.


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  • Created on 02/03/2000
  • Last Modified on 12/06/2004
  • Last Modified by Administrator.
  • Article has been viewed 9332 times.