Understanding NEC Article 694: Wind Electric Systems

NEC Article 694 outlines safety and operational standards for wind electric systems, encompassing one or more wind turbines along with their associated equipment such as generators, inverters, controllers, and storage devices. These systems may operate as standalone units or interact with other power sources.

Scope of Article 694

This article applies to:

• Wind electric systems used to supply buildings or structures.
• Systems with alternating current (AC) or direct current (DC) outputs, including those with energy storage like batteries.

Examples:

• Onshore and offshore wind farms.
• Residential or commercial wind turbine installations.

Key Requirements for Wind Electric Systems

1. Construction and Maintenance (694.7)
   • Installations must be performed by qualified persons trained to manage the unique hazards of wind systems, such as confined spaces and elevated work areas.
2. Overvoltage Protection (694.10, 694.12)
   • Surge Protective Devices (SPDs) are required to protect systems from lightning and power surges.
   • Conductors and overcurrent devices must handle at least 125% of the maximum circuit current.
3. Disconnecting Means (694.20, 694.22)
   • Means to disconnect all conductors must be installed at accessible locations.
   • Disconnect switches must display warning labels to prevent accidental contact with live parts.
4. Grounding and Bonding (694.40)
   • All non–current-carrying parts, such as towers and nacelles, must be bonded to the grounding system.
   • Galvanized grounding electrodes are recommended to prevent corrosion in specific soil conditions.
5. Working Clearances and Safety (694.7(G))
   • Clearances for electrical cabinets and turbine components must meet or exceed NEC requirements.
   • Flexible cords and cables used for moving turbine parts must be extra-hard usage, sunlight resistant, and suitable for outdoor environments.
6. Energy Storage and Overcurrent Protection (694.52, 694.15)
   • Systems with batteries must be clearly marked with operating voltages and polarity.
   • Overcurrent protection devices must be listed for DC use where applicable.

Additional Features and Marking

1. Manual Shutdown (694.23)
   • Turbines with a swept area exceeding 50 m² require manual shutdown switches.
   • Shutdown instructions must be posted near turbine controllers or disconnects.
2. Connection to Other Power Sources (694.60, 694.62)
   • Only listed interactive inverters may be used for grid-tied systems.
   • Wind systems interacting with other sources must comply with Article 705.

Applications

NEC Article 694 supports the safe deployment of wind electric systems in:

• Utility-Scale Wind Farms: Power generation for grids.
• Commercial Use: Supplementary or primary power for businesses.
• Residential Installations: Wind turbines for homes or small communities.

Conclusion

NEC Article 694 provides a robust framework for the safe installation and operation of wind electric systems. By addressing grounding, overcurrent protection, disconnecting means, and marking requirements, the article ensures these renewable energy systems operate efficiently and safely.