MV Overhead Line Ampacity

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gray.one

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I'm not clear on which table in the NEC should be used for an open wire overhead line that is medium voltage.

Table 310.15(B)(21) seems to be the only one that applies to this setup, but it is for LV according to article 310.15(B).

Since the conductor is not insulated, I don't understand why there would be any difference for LV and MV.

Thank you for your help.


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ramsy said:
According to industry standards for medium voltage:
http://www.highvoltageinfo.com/2007/07/what-is-medium-voltage_13.html

Start with NEC 310.60(B), but my preference would be under engineering supervision.
Click to expand...
The NEC breaks conductor ratings up into under 2000 V and 2001V to 35,000V. I'm working with 13.8kV.

The tables in 310.60 are at best insulated cable in free air.

Logically, 310.15(B)(21) should work, but the text seems to say otherwise.


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gray.one said:
The NEC breaks conductor ratings up into under 2000 V and 2001V to 35,000V. I'm working with 13.8kV.

The tables in 310.60 are at best insulated cable in free air.

Logically, 310.15(B)(21) should work, but the text seems to say otherwise.
Click to expand...
I agree.

According to your profile, you are an engineer. Provide engineering supervision. :D
 
gray.one said:
The tables in 310.60 are at best insulated cable in free air.

Logically, 310.15(B)(21) should work, but the text seems to say otherwise.
Click to expand...
Why bother with table complications that omit conductor temperature, if you have cable specs., and certified formulas under engineering supervision?
 
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