It seems far-fetched: A high-voltage line sags near a tree and cuts power to millions across the American West. But it happened this summer - twice - and utility watchdogs warn it could happen again.
Soaring demand, industry deregulation and complex trades of electricity across the West are making the nation’s biggest power grid more prone to widespread failure, the watchdogs say.
“Under no circumstance should this happen, let alone twice in one summer,” said Bob Jenks, executive director of the Citizens Utility Board in Portland. “A tree shouldn’t be able to cause the power system across the American West to go down.”
The first blackout occurred July 2, when hot weather made a 345,000-volt power line in Idaho droop too close to a cottonwood tree. An electrical arc short-circuited the line, and during the next 35 seconds, one line after another went out across the West, cutting power to 2 million customers in 14 states.
Last Saturday’s outage was even bigger, affecting 4 million homes and businesses throughout the West. It also started with a line sagging toward trees, this time in Oregon. The resulting short circuit triggered a chain reaction that shut down the main Pacific connection between the Northwest and California.
In both cases, the blackouts might have been smaller if not for the power grid that lets utilities trade electricity around the region, moving it from where supply is the cheapest to where demand is the greatest.
The West’s interconnected system, with 88 member utilities and more than 112,000 miles of transmission lines across 14 states, covers the most territory of any of the continent’s nine regional grids.
In the July 2 outage, sweltering residents of Utah, Idaho and California were turning on air conditioners and drawing huge amounts of electricity supplied by dams in the Northwest and coal-fired plants in Wyoming and Utah.
Last Saturday’s outage still is under investigation, but what officials do know is that it was a case study in the domino effect:
At 2:01 p.m. Saturday, a sagging transmission line sent an arc of electricity into the trees 60 miles east of Portland. The line short-circuited, and the resulting surge of electricity knocked out two other lines in Oregon during the next 50 minutes.
At 3:42, another sagging line short-circuited over a filbert orchard just west of Portland. Five minutes later, two units at the McNary hydropower dam on the Columbia River sensed the system’s instability and shut down automatically. One minute after that, voltage fluctuations shut down the main connection from Oregon to California.
Utility officials defended the system as an efficient way to balance supply and demand - especially as the West, the nation’s fastest-growing region, continues to demand more electricity.
“If each part of the region had to build power plants to meet peak demand, we’d have power plants that were idle most of the time,” said Dulcy Mahar, spokeswoman for the Bonneville Power Administration, which markets Columbia River hydropower.
But watchdog groups are concerned that power outages may become more common as deregulation increases the number of energy suppliers using the grid to transmit power.
The reality, if not monitored closely, could be messy, said Bob Finkelstein, attorney for a San Francisco-based consumer group called Toward Utility Rate Normalization.
“The system that’s been unusually taxed twice this summer is going to be facing even heavier traffic in the next few years,” Finkelstein said.
Mahar, conceding “there’s a brittleness in the system,” said utilities this week are taking steps to head off more blackouts.
“They may no longer be aberrations because of high power use and the complexity of the system,” Mahar said. “It’s clear there’s a bug in the system, and we’re going to track it down.”