Life expectancy of underground wire

[ChillerGuy]

Any data on expected life expectancy on underground cable? (460/3/60)

 

[dpc]

At that voltage, life expectancy is probably much longer than yours provided it wasn't damaged during installation and isn't overloaded too drastically. There isn't enough voltage to create the dielectric failures that plague high-voltage cables.

Should easily be 50 years.

 

[DRWeig]

dpc's answer is a good one. We have a bunch of buried 480/3 that's a lot older than I am. It seems that the only real life-shorteners for such installations involves backhoes.

Old Dave

 

[aolalde]

The life expectancies will be linked to the operating temperature rise.
If the circuit is not abused (overloaded) it will last those fifty or more years.

 

[dpc]

Yes, I should have mentioned that dig-ins are probably the biggest threat. Thanks DRWeig.

 

[rbulsara]

Also how it is buried also affects life-expectancy of the cables.

A cable in a underground ductbank, concrete encased would afford greater protection to phycial damage than the direct burial ones.

Also cable buried deeper (at least code recommended depths), and below frost lines would last longer than shallow ones.

Cable buried in more hostile enviornmnet like desert may not last as long as ones in cooler (but not wet) terrains.

In short, too many variables. But if installed properly, opinions stated above are as good as any.

 

[mc5w]

Also depends on the Tree Root Circuit Breaker Method and the Rock Circuit Breakers Method. Summit County, Ohio Building Department outlawed direct burial electrical services in 2002 because too many failure occurred.

Sure, National Electrical Code allows direct burial but by the time I remove rocks from the trench and the backfill it is easier to stick in a conduit (preferably oversize) and put direct burial cable in it.

Also, 2-legged gophers never ever see the warning ribbons that we install. When that happens we make the 2-legged gophers pay through the nose for repairs.

 

[Marke]

Buried cables need to be rated for the conditions where they are buried. There was an instance not too long ago where major buried cables failed because the ground was so dry that it did not offer any thermal conductivity and the cables overheated.
Provided that the burial site is very stable so that no mechanical damage will occur to the insulation, the major factor influencing the life of the cable is thermal and it must be rated to the worst case thermal conditions of the ground in which it is buried.
Best regards,

Mark Empson

http://www.lmphotonics.com

 

[mc5w]

Also, if you bury your cable TOO deep it will not be able to dissipate heat. Also, unless you have a way to level the bottom of the trench you may have to lay in a direct burial cable that is 1.5 to 2 times the length of the trench so that the cable can conform to the bottom of the trench.

The last time that I changed out an underground electrical service Verizon's technician paid out a length of underground telephone cable about 1.5 times the length of the trench.