Best Practices
small wind and the 2011 national electric code
Article 694 has been published. It’s time to learn about it. By MICK SAGRILLo
mick sagrillo (msagrillo
@ wizunwired.net) of
sagrillo Power & light is
a small-wind consultant
and educator.
While the National Electric Code (NEC) applies to any electric equipment, wiring or device that is connected to the national electric grid, it wasn’t
until 2010 that an article specific to the unique characteristics
of grid-interconnected and battery-charging small wind turbines was adopted. The development of Article 694 began in
March 2008 and it was finally accepted in June 2010 by the
National Fire Protection Association, the folks who update
and publish the NEC as an ANSI Standard.
Over that time, 50 stakeholders from across the country and representing many more disciplines than small
wind provided input and guidance for the draft document.
Dr. Rob Wills, PE, of WindMonitoring.com and Rob-
ert Preus, PE, of
Advanced Renew-
able Technology
LLC, co-chaired
the Wind-NEC
code-writing com-
mittee. For their
efforts, they were
recognized last
June by Wind Pow-
ering America with
the Small Wind
Advocacy Award
at the 2010 Small
Wind Conference
in Wisconsin.
Like other sec-
tions of the NEC, you will likely need to review Article
694 many times before you are able to absorb all of its
ramifications. Briefly, the sections of Article 694 encom-
pass the following:
•;Section I covers definitions and the scope of Article
694. “Small wind turbines” are defined as those up to and
including 100 kilowatts in nameplate capacity at 11 meters
per second ( 24. 6 mph) wind speed. All wind turbines that
generate electricity, regardless of blade orientation, tower
style or where they are mounted, are covered by Article
694.
• Section II elaborates on circuit requirements,
including voltage and current limitations as well as conductor and over-current protection sizing. As Article 240
focuses on over-current protection requirements, that
article is referenced.
•;Section III goes over the details of disconnecting
the wind turbine from the electrical system. Some wind
turbines are designed to never be disconnected from their
load, lest rotor rpm increase uncontrollably. This section
seth masia
Patterned very roughly
on Article 690, the new
code has important
differences. For instance,
over-current protection is
scaled for continuous at-capacity operation.
44 March 2011 SOLAR TODAY solartoday.org
Copyright © 2011 by the American Solar Energy Society Inc. All rights reserved.
recognizes that unique feature of small-wind technology,
with an exception for turbines that would be deleteriously
affected by the incorporation of a “disconnecting means.”
•;Section IV reviews allowable wiring methods for
small wind turbines.
