What cable standards apply to wind turbines?
As the power industry has evolved with increased use of renewable-energy, so have wind-cable industry standards and the types of cables manufactured to meet the requirements of wind applications. The first available wind-cable solutions represented innovative and customized designs to meet performance requirements for increased flexibility and resistance to high-torsion stress, vibration, oils and abrasion.
As the renewable-energy market matures, industry standards organizations are recognizing traditional cables that provide the same long-term performance and reliability as R&D intensive, application-specific, wind-cable constructions.
Early solutions were often regionalized into North America (NA) from IEC designs due to the lack of NA wire and cable standards to support a predominant European wind-turbine manufacturing and design base. For instance, wind turbine OEMs specified cross-linked 90°C rated cables for multi-conductor jacketed power-cable applications supplying auxiliary power within the nacelle. The cables selected were aligned with classifications for power cable (IEC 60502-1 or UL 44) or rubber cord (HD 22.12 or UL 62), carrying different flame ratings. An alternative class of traditional cable insulation found within NA standards (UL 83) known as Type THHN/THWN (PVC/Nylon) offers the same 90°C temperature rating and the higher wet rating available with cross-linked power cable classifications. Only single layer coverings of PVC rated up to 70°C are covered within IEC 60502-1 making this option inadequate for the application.
Currently, both copper and aluminum alloy conductors with thermoset and thermoplastic insulation are generally accepted for wind-turbine applications. But cable guidelines and standardization for renewable-energy applications are improving. Industry standards organizations such as the National Fire Protection Association (NFPA), the Canadian Standards Association (CSA) and Underwriters Laboratories (UL) are recognizing wind-farm cables in publish codes and standards guidelines.
UL 6141, for example, will require that all wiring within a wind turbine accessible to users or service personnel, or running vertically up the tower, be in a raceway and of a cable type listed below with a flame rating such as CT or FT4:
- Outline of Investigation for Flexible Motor Supply Cable and Wind Turbine Tray Cable, UL 2277
- Standard for Power-Limited Circuit Cables, UL 13
- Standard for Optical Fiber Cable, UL 1651
- Standard for Thermoplastic-Insulated Wires and Cables, UL 83, or the Standard for Thermoset-Insulated Wires and Cables, UL 44
- Standard for Medium Voltage Power Cables, UL 1072 Metallic shields will be required for these cables to be compliant with UL 1072
- Standard for Flexible Cords and Cables, UL 62
- Standard for Cables for Non-Power-Limited Fire-Alarm Circuits, UL 1425
- Standard for Metal-Clad Cables, UL 1569
Most traditional North American cable types will soon be specifically permitted within wind-turbine standards, and will effectively level the selection and performance ratings by establishing consistent flame performance.
By: Tim Clancy, Renewables Engineering Manager, General Cable