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vault backup: 2026-03-09 15:01:01

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Zane Meyers
2026-03-09 15:01:01 -04:00
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nfpa-70_311_mv-conductors.md
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@@ -61,12 +61,10 @@ Conductor application and insulation shall comply with Table 311.10(A).
\*Where design conditions require maximum conductor temperatures above 90°C.
#### 311.10(B) Thickness of Insulation and Jacket for Nonshielded Insulated Conductors.
Thickness of insulation and jacket for nonshielded solid dielectric insulated conductors rated 2001 volts to 5000 volts shall comply with Table 311.10(B).
##### Table 311.10(B) Thickness of Insulation and Jacket for Nonshielded Solid Dielectric Insulated Conductors
Rated 2001 Volts to 5000 Volts
@@ -167,7 +165,6 @@ Level mm mils mm mils mm mils mm mils mm mils mm mils
1 7.11 280 8.76 345 11.30 445 — — — — — —
1/0–2000 7.11 280 8.76 345 11.30 445 8.76 345 10.67 420 14.73 580
#### 311.10(C) Thickness of Insulation for Shielded Insulated Conductors.
Thickness of insulation for shielded solid dielectric insulated conductors rated 2001 volts to 35,000 volts shall comply with Table 311.10(C) and 311.10(C)(1) through (C)(3).
@@ -194,13 +191,9 @@ Cables shall be permitted to be applied under all of the following conditions:
Cables shall be permitted to be used in 100 percent or 133 percent insulation level applications where the installation requires additional insulation.
##### Table 311.10(C) Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors Rated 2001 Vol
2001–
5000
Volts 5001–8000 Volts 8001–15,000 Volts
2001–5000 Volts 5001–8000 Volts 8001–15,000 Volts
Conductor
@@ -267,8 +260,8 @@ Leve mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm m
2 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 — —
1 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 2
1/0–2000 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 2
### 311.12 Conductors.
### 311.12 Conductors.
#### 311.12(A) Minimum Size of Conductors.
@@ -400,8 +393,6 @@ Type MV cable terminated in equipment or installed in pull boxes or vaults shall
Nonshielded, ozone-resistant insulated conductors with a maximum phase-to-phase voltage of 5000 volts shall be permitted in Type MC cables in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation. For other establishments, solid dielectric insulated conductors operated above 2000 volts in permanent installations shall have ozone-resistant insulation and shall be shielded. All metallic insulation shields shall be connected to a grounding electrode conductor, a grounding busbar, an equipment grounding conductor, or a grounding electrode.
> [!info] Informational Note:
> The primary purposes of shielding are to confine the voltage stresses to the insulation, dissipate insulation leakage current, drain off the capacitive charging current, and carry ground-fault current to facilitate operation of ground-fault protective devices in the event of an electrical cable fault.