On August 10, 1996, a massive power outage struck Western North America, knocking out power in several U.S. states, two Canadian provinces and Baja California during a heat wave. In less than two hours, five high voltage power lines came into contact with trees in Oregon and Washington and a domino effect took out dozens of critical power lines as well as large electricity generating units from British Columbia and Alberta in Canada to New Mexico and Baja California. Since the nature of electricity is to flow in the most efficient direction (or path of least resistance), a tree can give it a way to flow straight to ground, interrupting power flow and causing breakers to trip when they sense a problem on the line. One such incident can impact a relatively small area, but a series of outages such as occurred in 1996 is a serious problem.
Power was out from a few minutes to six hours in California, according to a California Energy Commission survey, and the Union of Concerned Scientists says approximately 7.5 million people overall were affected by the power failure. According to the Federal Energy Regulatory Commission, those affected were located in the Canadian provinces of British Columbia and Alberta, the states of California, Arizona, New Mexico, Oregon, Nevada, Texas, Idaho, Colorado, Montana, South Dakota, Nebraska, Utah, Wyoming and Washington, and Mexico’s Baja California.
What we and other utilities learned from this outage is that we need to proactively address hazards. We know that tree limbs cause outages, and we know that old and outdated equipment such as power poles and cross arms can fail. Trimming tree limbs before problems occur has long been part of our ongoing commitment to reliable delivery of electricity.
That’s why we encourage our customers to let us know if they see a branch that appears too close to a power line; we’ll inspect it and trim it if it’s a problem. We’ve also hired a company to accelerate our continuing replacement of power poles and cross arms, many of which are over 40 years old.
This ongoing methodical program of maintenance and system upgrades will continue for a few years, and it will increase our reliability and decrease the possibility of an unexpected power outage that can be inconvenient at best and create dangerous traffic and health facility problems at worst.