In the Cable Chronicles series, we have already talked about the history of solar power as a renewable energy source and the progression of solar cable standards. This time we are going to breeze through another green energy source with a long history— wind power! Let's take a look at the wind cable standards that have come along with it.
A Brief History
There are records of humans harnessing wind energy to propel their boats as early as 5000 B.C. Windmills got their start pumping water and grinding grain by 200 B.C. Even electricity-producing windmills have been around for some time, the first ones popping up in Denmark in the late 1800s. Wind turbine cable standards, on the other hand, have seen most of their development over the past decade.
Developing Wind-Specific Cables
Not too long ago, there was no such thing as a dedicated “wind turbine cable.” Wind turbine designs called for other common cables, like welding cable, DLO Cable, SOOW, and SJOOW portable cord, XHHW cable, and RHH/RHW cable, but wind applications demanded more than these products could provide.
Wind developers began to engineer wind turbine cables with qualities that enhance efficiency and longevity: strong torsional and bending flexibility and resistance to electromagnetic interference, high winds, extreme temperatures, UV light, chemicals, oils, and even salt spray in some applications.
Now we have all kinds of wind farm cable available from many manufacturers. Instead of using TC-ER cable rated to only 600 volts, wind farmers can use WTTC rated cable, good to 1000 volts. There are wind turbine cables with various flex levels: Standard, Premium, and MegaFlex. You can also get WTTC rated Servo cable and VFD cable, designed to withstand the particular challenges of the wind power industry.
With new wind cable products on the market, new standards became increasingly necessary. For some time, one of the only wind turbine component-specific ratings out there was UL 2277 for Wind Turbine Tray Cable (WTTC Cable). Many other common cables used in wind turbines, like those listed above, have been subject only to the generic provisions of the National Electric Code (NEC). A few regulations pertinent to wind turbine systems were lumped in with Article 705 of the NEC, a section mostly applicable to photovoltaic systems.
In 2011, the NEC added Article 694, which pertained mostly to small wind turbine systems. The 2014 version expanded to include large systems as well. The UL covers Wind Turbine Generating Systems (WTGS), smaller Wind Turbines (WT), and their components under UL 6140, 6141, 6142, and 6171.
These standards will continue to evolve rapidly as new components and methods are adopted. For example, in the last few years, there has been some experimentation with fiber optic cables in almost all components of a wind turbine generation system. If that takes off, maybe we will see something addressing it more specifically in the 2017 NEC! Until then, you can learn more about WTTC rated wind cables here.