Damaged electric distribution lines were the major cause of the widespread Northeastern customer outages during the October 2011 snowstorm, but utilities can apply lessons learned from the storm to improve performance and enhance reliability of their transmission lines in advance of the next storm, staff of the Federal Energy Regulatory Commission (FERC) and North American Electric Reliability Corporation (NERC) said last month.

Staff of both FERC and NERC issued a joint report on the transmission outages on May 30. The joint inquiry focused on determining the causes of the transmission facility outages and on the steps utilities could take to improve their performance in maintaining grid reliability during the next large snowstorm or similar weather event. The purpose of the inquiry was not to investigate whether particular companies violated FERC-approved reliability standards or other applicable statutes and regulations.

The report finds 74 transmission lines and 44 transmission substations experienced outages. These problems along the transmission system caused less than 5 percent of customer outages at the peak of the Oct. 29-30 storm, which left more than 3.2 million homes and businesses without power. Most of these transmission-caused customer outages lasted fewer than two days and none lasted more than five days. Nearly three-quarters of the transmission line outages occurred when healthy trees, most located outside of utility rights-of-way, fell onto the lines uprooted by the weight of the snow compounded by the soft, wet ground. The report offers several recommendations to help reduce the adverse impacts of future weather events on the transmission system, including:

  • Where appropriate, take targeted steps to address off-right-of-way danger trees;
  • Employ best practices in managing vegetation on full rights-of-way;
  • Lay the foundation for effective vegetation management when establishing new rights-of-way;
  • Enhance storm preparedness and response plans as needed. The joint report also recommends increasing the reporting of vegetation-caused outages and improving the content of required disturbance reports.