rmullin
Electrical
- Nov 2, 2006
- 4
I am sizing cables to NEC for an LNG Facility in Peru, following the rules from Article 310 of NFPA 70. The cables must be direct buried. From the main 13.8kV Switchboard there are 28 feeders to transformers (14 from bus A and 14 from bus B). Here, the probelm arises. From NEC Figure 310.60, it stipulates that there must be a 24 inch (600mm) centre-to-centre spacing between circuits. For this application we have numerous feeders in the same trench, and having to separate each circuit by 24 inches creates a huge problem in terms of trench size. Typically how would this problem be overcome? Is it possible to have multiple layers of MV cables, whilst complying with NEC? (Im used to sizing cables to British Standads or IEC, therefore I think I may be missing something in my interpretation of the NEC, as these standards do not require such a large separation distance). Thanks in advance.