Photo credit: Dominion
The 2013 sniper attack on Pacific Gas & Electric Company’s Metcalf transmission substation was a wake-up call for the electric power industry. A team of riflemen knocked out the facility near San Jose, Calif., by firing upon and severely damaging 17 transformers. Thanks to redundancy in the grid, PG&E was able to prevent blackouts by re-routing electrical power. But the incident drove home how vulnerable the electric grid is to sabotage.
“The next day,” recalls Mike Lamb, manager of operations engineering for Dominion Energy Virginia, “we started brainstorming about what resiliency improvements we needed.”
As part of a multi-pronged strategy to bolster resiliency of its 6,500-mile electric transmission lines, 57,000 miles of distribution lines, 900 substations and 66,000 transformers, Dominion procured mobile transmission equipment designed by manufacturers in Europe, Asia and North America. The mobile equipment provides a “plug and play” design that allows it to connect with high-voltage cables in a fraction of set-up time required by conventional technology.
Most of the equipment held in resiliency reserves sits idle until needed in the aftermath of a hurricane, earthquake, or human-caused event. As it turned out, has Dominion found a use for the trailer-borne transmission outside of an emergency situation.
Temporary substation on the job in the Cartersville transmission line rebuild.
The company had a “wreck-and-rebuild” job on an older transmission line between the Bremo Power Station and a substation in Cartersville. Typically, says Lamb, a temporary transmission line would be constructed to carry load to customers while the old line was being rebuilt. In this particular case, a five-mile section had poor access.
Besides saving the $4 million expense of stringing a temporary line, says Lamb, the company was able to conduct a “proof of concept.” Workers proceeded slowly and deliberately over four months in order to work out set-up processes and develop checklists.
“We accomplished a lot of things with this one installation,” Lamb says. “If we have an unplanned situation in the future, we could hopefully make it within five to seven days.”
Nationally, the electric grid is aging. Most transformers in the United States were installed between 1950 and 1970, and have far exceeded their expected 40-year life span. U.S. utilities, some fear, may be forced to contend with an increasing number of breakdowns. Thus the grid is growing more fragile even as the threat of sabotage, cyber attacks and natural disaster looms ever larger.
While Dominion says that it has been proactively replacing older transformers, substation equipment, and transmission lines in order to improve reliability, the mobile transmission equipment gives it an added safeguard against an extended outage.
“The installation of the mobile transmission substation in Cartersville was a first in North America, and the equipment operated as designed,” says Lamb. “Dominion will definitely be better equipped and prepared in the future to respond to unplanned events.”