Outdoor Overhead Conductors over 1000 Volts
- Scope. This article covers the use and installation for outdoor overhead conductors over 1000 volts, nominal.
- ARTICLE 399 — OUTDOOR OVERHEAD CONDUCTORS OVER 1000 VOLTS
Outdoor Overhead Conductors. Single conductors, insulated, covered, or bare, installed outdoors on support structures in free air.
399.10 Uses Permitted. Outdoor overhead conductors over 1000 volts, nominal, shall be permitted only for systems rated over 1000 volts, nominal, as follows:
- Outdoors in free air
- For service conductors, feeders, or branch circuits
Informational Note: For additional information on outdoor overhead conductors over 1000 volts, see IEEE C2-2012, National Electrical Safety Code, and ANSI/IEEE 3001.2, Recommended Practice for Evaluating the Electrical Service Requirements of Industrial and Commercial Power Systems.
- Conductors. Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems for the spacing between conductors shall be available upon request of the authority having jurisdic‐ tion and shall include consideration of the following:
- Applied voltage
- Conductor size
- Distance between support structures
- Type of structure
- Wind/ice loading
- Surge protection
- Structures. Structures of wood, metal, concrete, or combi‐ nations of those materials, shall be provided for support of overhead conductors over 1000 volts, nominal. Documentation of the engineered design by a licensed professional engineer engaged primarily in the design of such systems and the instal‐ lation of each support structure shall be available upon request of the authority having jurisdiction and shall include considera‐ tion of the following:
- Soil conditions
- Foundations and structure settings
- Weight of all supported conductors and equipment
- Weather loading and other conditions such as, but not limited to, ice, wind, temperature, and lightning
- Angle where change of direction occurs
- Spans between adjacent structures
- Effect of dead-end structures
- Strength of guys and guy anchors
- Structure size and material(s)
- Insulators. Insulators used to support conductors shall be rated for all of the following:
- Applied phase-to-phase voltage
- Mechanical strength required for each individual installa‐ tion
- Impulse withstand BIL in accordance with Table 490.24
Informational Note: 399.30(A), (B), and (C) are not all- inclusive lists.