Cable
Designs to Meet Wind Turbine Industry Standards
Over the last several decades, wind
turbine installations have dramatically increased. As their use has become more
widespread, they have evolved in both efficiency and complexity. Today’s wind
turbines are comprised of a vast array
of sophisticated components that are
subject to damage from the harsh environments in which they operate. Among the
most critical and overlooked components in turbine systems are the cables that
handle the power and data transmission.
Because they can fail when exposed to
the temperature extremes, chemicals and electromagnetic interference (EMI) found
on wind turbines, cables for the wind energy applications must be selected very
carefully. They must also be tested rigorously to make sure they meet industry
standards.
Here’s an update on the current state
of standards for wind turbines in North America, as well as a more in-depth
look at the factors design engineers should consider when selecting cabling for
wind turbine applications.
INDUSTRY CODE CHANGES
IN NORTH AMERICA
As the use of wind turbines in
industry and commercial applications becomes more prevalent, there is a growing
need to ensure their proper installation
and safe operation, which has prompted mandates to provide clearly written
safety standards. While utility companies are monitored by government agencies,
non-utility applications are guided by the National Electrical Code (NEC). In
2011, a new section called Article 694 was added to the NEC to ensure
installation safety of small wind electric systems. NEC Article 694 covers
small wind power single turbines that are rated for 100 Kilowatts (0.1KW).
There is no limit to the number of wind turbines that can be installed in a
given location. When several of these machines populate the same location, it
is referred to as a “wind turbine farm” which can cover an area of several
hundred square miles.
To establish consistency and to
prevent confusion, UL has drafted several subjects corresponding to wind
turbine generating systems: UL Subject 6141: Large Wind Turbine Systems (WT)
and Electrical Subassemblies, and UL Subject 6142: Small Wind Turbine Systems
(WT) and Electrical Subassemblies. Wind turbines with entrance access are defined
as “large” per UL 6141. They are grid-connected and are used for “utility”
applications. Wind turbines without entrance access are defined as “small” per
UL 6142. They are not connected to the grid and are considered “non-utility.”
As the industry grows and the emphasis towards revision of standards continues,
UL 6141 and 6142 will be upgraded to include new requirements.
In addition, there are corresponding
UL Standards that focus on specific internal components within the wind
turbine. For example, Rotating Electrical Machines must meet UL Standard 1004–1.
Electric Generators have to meet UL Standard 1004–4, and so forth. In UL
Standard 1004–1 AWM, cables are permitted, but only with exceptions. Section
20.2 allows the use of either standard building wire or appliance wiring
material (AWM). Section 20.4 permits AWM, provided it has an insulation thickness
appropriate for the insulation material type and meets stringent cable
construction requirements. As UL Standard 1004–1 allows for the AWM option,
building wire is a “listed” product, automatically qualifying it as an NEC
compliant wiring method. It’s worth noting, however, that AWM is not an NEC
acceptable wiring method, so it may be
subject to potential acceptance issues during an inspection.
Within the construction of the wind
turbine, cable trays or raceways route and support cables to accommodate power for the various operating systems. To
address safety concerns about performance of these cables under operating
conditions inside the wind turbine, UL released an outline of investigation for
“Flexible Motor Supply Cable and Wind Turbine Tray Cable.” This Outline,
referred to as UL 2277, permits a 1,000 Volt rating and specifies safety and
performance requirements for cable intended to be installed within a tray or
raceway in the wind turbine. UL 2277 mandates that cables used in a cable tray
or raceway in the wind turbine must also meet all performance criteria of UL
1277, known as the “Tray Cable” standard.
Download the full version of the Whitepaper
Visit our website
Like us on Facebook
Join our Linkedin Network
Watch us on Youtube
There is a chance you're eligible for a new government sponsored solar energy program.
ReplyDeleteClick here to discover if you qualify now!