JEFF MILLAR
Senior Member
Can you share your NEC. step by step instructions for sizing 15 KV. 3 core copper , shielded , 133 %. cable with a 320 amp load directly buried in the ground.
HOW TO SIZE A 15 KV 3 - 1/C. CABLE DIRECTLY BURIED IN THE GROUND
- Thread starter JEFF MILLAR
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Julius Right
Senior Member
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- Electrical Engineer Power Station Physical Design Retired
Table 310.60(C)(83) Ampacities of Three Insulated Copper Conductors Cabled Within an Overall Covering (Three- Conductor Cable), Directly Buried in Earth Based on Ambient Earth Temperature of 20°C (68°F), Arrangement per Figure 310.60(C)(3), 100 Percent Load Factor, Thermal Resistance (RHO) of 90, Conductor Temperatures of 90°C (194°F) and 105oC and 5001–35,000 Volts.
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| (1) Grounded Shields. Ampacities shown in Table 310.60(C)(69), Table 310.60(C)(70), Table 310.60(C)(81), and Table 310.60(C)(82) shall apply for cables with shields grounded at one point only. Tables other than those listed contain |
| the ampacity of cables with shields grounded at multiple points. |
| From Table 310.60(C)(83) for voltage of 5 to 35 kV 4/0 withstand 350 A at 90 oC., [one single 3 cores underground cable in 30-36 fts of 90 rho soil]. |
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