Voltage Insulation Level UG Cable

[ePOWEReng]

Hello. What is the proper voltage insulation level for a NEC application running a 6.6kV motor? Using the utility theory, you go by the line-line voltage so we would probably need to buy 15kV cable. Right? But do the same criteria apply to a single 3-phase UG feed to a pump? Does the insulation level still need to be based on line-line do to faults?

Thanks for the help!

 

[dpc]

Yes, you should insulate based on line-to-line voltage. I believe you can buy 8 kV cable.

 

[cuky2000]

Cable insulation is based not only on the line-to-line voltage but also the thickness of the insulation is related with the clearing time of the protection system such as 100% Insulation for t<1min, 133% thickness for t<1hr and occasionally 173% for t> 1 hr.

For system voltage line-to-line >5 kV, most cabling systems are also shielded.
See the enclose reference sample:
a) Single rated: 8kV Unshielded 100% Insulation up to 90o C:

http://www.okonite.com/Product_Catalog/section2/sheet3.html

b) Double rated: 5/8 kV shielded 133%/100% insulation 105 o C:

http://www.okonite.com/Product_Catalog/section2/sheet4.html

c)Single rating: 8 kV shielded 133% insulation 105 oC

http://www.okonite.com/Product_Catalog/section2/sheet7.html