Too much cable, coiled in Switchboard 2

[NSee]

Thought I would post this for general comments. Yesterday I inspected a 4000A, 480/277V, 3ph, 4 wire switchboard installation. The day-before, the cables (13 sets 500kcmil) had been pulled out to a utility company, pad-mount xfrmer and also terminated at the landing lugs of the board.

Problem is, the contractor pulled what looks to be 20 to 25feet of extra cable and just had it all coiled up in the bottom of the switchboard section. 13 sets x all the footage....Its a mess.

Anyone ever see anybody do that? In over 25 years of consulting practice, I've never seen that. Besides some additional voltage drop, it looks like a big AC choke, inductance, not to mention a rat's nest.

I'm writing the report now and directing them to not energize the transformer until this is undone, cut to a reasonable length, assure same distance on all parallels, and then reconnect.

 

[racookpe1978]

I actually saw that used on some feeders that were 12 inches too short. Many years ago at the start of my career, you don't want the details!! We didn't have the regulation "Left Handed Cable Stretcher".

Be very careful..

On some of today's newer jobs, you have to specify the "Metric Left Handed Cable Stretcher".

(Always be sure to double-check the calibration date on any cable stretcher before you issue it to the apprentice. They go out of date faster than you'd think. Just like those calibrated Metric Counter-clockwise Crescent Hammers the millwrights need to use to quickly round off bolt heads.)

 

[Skogsgurra]

PLS for you, racoo.

There are no fixed limits for when to use and not to use. It all depends on total cable length, if level differences are present, ambient temperature - especially if there's load and/or temperature cycling - and several other factors that an experienced cable team intuitively knows about.

In general, though, it is wise not to stretch more than about one foot. We agree there.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[controltechnician]

jraef (Electrical) said "I have had issues with coiled conductors acting as inductors and causing serious voltage drop. But they were hundreds of feet left on a reel (cheap user wanted to return it un-cut when the temp job was over). I don't think 4 or 5 loops in air would add significant inductance. "

a little inductance during normal operation is not a problem, but under fault conditions it could delay the opening of the circuit protectors, and allow a dangerous situation to linger a few moments longer.