No transmission line outages were caused by vegetation growing into the lines from within the rights-of-way between the months of July and September 2009, a first in the six years the North American Electric Reliability Corp. has tracked this data, the organization reported. The majority of vegetation-related transmission line outages typically occur over the summer months due to seasonal tree and shrub growth. In comparison, five such transmission outages were reported in the third quarter of 2008.

“Managing vegetation around North America’s 350,000 miles of transmission lines is a challenge that never ends,” commented Rick Sergel, president and CEO of NERC. “I commend transmission owners and operators for this achievement, which clearly demonstrates the industry’s dedication to improving performance in this area. Our goal now is to produce consecutive quarters with no vegetation-related transmission outages or violations.”

Vegetation contact with multiple transmission lines was a primary cause of the Aug. 14, 2003, blackout that affected 50 million people in the United States and Canada. The blackout was a driver in the move to make bulk power system reliability standards mandatory and enforceable in North America. Compliance with NERC’s reliability standard on vegetation management (FAC-003-1) became mandatory in the United States on June 18, 2007, and is also mandatory throughout much of Canada. U.S. entities found in violation of this standard can be subject to penalties under Section 215 of the Federal Power Act.

NERC’s Third Quarter 2009 Vegetation-Related Transmission Outage Report, can be found online at: