Power Line Systems, Inc. 610 N. Whitney Way, Suite 160
Madison, WI 53705, U.S.A.
Phone: (608) 238-2171, Fax: (608) 238-9241
Email: info@powline.com
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Determining Structure and Wire Clearances

The advantage of using true 3-D software such as PLS-CADD is that the designer can see what will be built before the first structure is ordered. Clearances between conductors, conductors and structures, and even between conductors and communications cables can easily be checked for a variety of conditions to eliminate problems before they occur. This TechNote will briefly discuss how to use PLS-CADD and PLS-CADD/Lite to check clearances in a 3-D environment.

Wire Clearances

First, let's cover wire clearances. Wire clearances can be used in both the full PLS-CADD as well as PLS-CADD/Lite to check the clearances between any wires in a project, such as:

Many of these clearances need to be checked under a variety of possible line conditions. For example, that distribution underbuild or crossing may not always be energized when the transmission line is operating at its maximum temperature. The upper phase of a vertical circuit may have full ice on it while the middle phase may not. What could happen when one phase sheds the ice on it and then "jumps"? How do you check the NESC requirement that you must have different (larger) clearances at midspan? Or the different required clearances depending on whether or not the cables are attached to the same structures or different structures? PLS-CADD and PLS-CADD/Lite can check all of these conditions automatically for you.

Substation Slack-Span Roll Clearances - Click to see larger image.

Structure Clearances

Structure clearances are critical for obvious reasons. PLS-CADD or PLS-CADD/Lite can automatically check many different types of structure clearances for you. Would you rather catch an "overlooked" clearance with PLS-CADD while your project is still in the office or have it found by a lineman in the field? Clearances that can (and should) be checked are phase to:

See a video showing how PLS-CADD can be used to check structure and guy clearances.

Conductor to Substation Structures and Bus Clearances - Click to see larger image.

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