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Substation Equipment: Duct Runs

Duct Runs
Duct runs are hollow tubes running from manhole to manhole inside a conduit (see conduits) in an underground system. They are of various sizes usually from 2 to 6 inches in diameter. Electrical cables are run through ducts and the ducts are sized accordingly. The diameter of a duct should be at least 1/2 to 3/4 inch greater than the diameter of the cable(s) installed in the duct. They can be made of plastic (PVC), fiberglass, fiber, tile, concrete, or steel. PVC and fiberglass are most commonly used. 

Figure 1. Duct run showing drainage in both directions
Figure 1. Duct run within conduit showing drainage in
both directions 		Figure 2. Duct run on a grade
Figure 2. Conduit on a grade
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