Best practices quiz: answers for question page 5

Answer page 5 (of 5)

In the questions and answers below, "transmission" refers to installations on lines >100 kV and "distribution" refers to installation on lines < 100 kV. NESC refers to the National Electrical Safety Code which governs all electric utility installations in the U.S. (and any other jurisdictions that adopt it).

You can work through the questions on all 5 pages, then look at the answers; take the questions one page at a time followed by their corresponding answer page; or hop back and forth by following the shortcuts at the end of every question or answer. Finally, if, like many people, you get sick of all the clicking, you can just go to one long page with all the questions and answers.

#41. (Transmission) Is your ADSS cable at or above the elevation of any conductors at any point on any span? If so did you do blow-out checks at your local worst case windstorm and worst case ice storm to ensure the ADSS would not collide with the conductors (and possibly wrap around them)? Did you do these checks at intermediate wind speeds and ice loads? Did you do icestorm blowout checks with both ice on and ice-off conditions for your conductors? (Note, these questions don't apply to OPGW in the normal high position; they do apply if you underbuilt with OPGW or a similar metallic cable) (Shortcut back to question page 5)

See our page on transmission design page for more information -- all of these checks have to be made for each span to ensure cable to conductor collisions and entanglements do not occur as they have at some utilities.

#42. (Transmission) If you built with OPGW above your conductors, did you do OPGW to conductor clash studies for both ice on and ice off the conductors? (Shortcut back to question page 5)

See our transmission design page for more information -- both conductor icing scenarios have to be checked since resistive heating may or may not keep the conductors warm enough to be ice free.

#43. (Transmission - ADSS only) Did you perform an electric field analysis on all ADSS installations over 100 kV to ensure you won't have dry band arcing problems? If so, did you use isovolt plots or jacket current models or both? Did you correct the isovolt plots for tower line angle and insulator swing angles? Did you use the correct phasing in your model? If it was on a double circuit transmission line, did you run studies with one side de-energized? If another transmission runs parallel to this one in the same corridor, did you check to see if it had an effect on your transmission line? (Shortcut back to question page 5)

See our transmission design page. Isovolt plots at a minimum are required for all these scenarios and with the proper insulator and tower angle correction factors. Jacket current analysis is a new analytical technique we also use.

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