Underground Duct Bank Ampacity

[timm333]

I’m trying to find some solved examples for the underground cable in underground raceway (duct bank). It looks that these involve advanced thermal calculations done by software. Is it possible to do these calculations by hand using NEC tables? Thanks

 

[fmtjfw]

I’m trying to find some solved examples for the underground cable in underground raceway (duct bank). It looks that these involve advanced thermal calculations done by software. Is it possible to do these calculations by hand using NEC tables? Thanks

Have you looked at Annex B?

 

[timm333]

Yes Annex B has tables for underground duct bank. However books don't discuss the underground duct banks in detail. Is there a book or website which gives few solved examples for the duct bank ampacity?

 

[ron]

Google [h=1]Neher McGrath Calculation[/h]

 

[Smart $]

Also https://www.google.com/search?q=The...able+Systems+by+J.+H.+Neher+and+M.+H.+McGrath

 

[Julius Right]

See:
1) As ron said:
The Calculation of the Temperature Rise and Load Capability of Cable Systems by J.H.Neher and M.H.McGrath-October 1957
Appendix IV Calculations for Representative Cable Systems
Here it is a calculation for a 69 kV 1500 MCM single conductor oil-filled cable in duct.
2) IEC 60287-2-1 Electric cables –Calculation of the current rating
Part 2-1: Thermal resistance – Calculation of thermal resistance
2.2.7 Cables in ducts or pipes