It’s an unexpected sight.
A helicopter appears over the horizon and heads for a line of electrical transmission towers that stretch across the oak woodlands and cattle ranches east of Santa Margarita. It approaches one of the towers and a 30-foot boom swings out from its side and begins squirting high-pressure water on columns of ceramic discs hanging between the electrical lines.
The process only takes a couple of minutes and then the helicopter moves on to the next tower. In a typical day’s work, the chopper will hose down 150 Pacific Gas and Electric Co. transmission towers.
“They don’t wash the entire line,” explained Blair Jones, PG&E spokesman. “They just wash off the insulators between the lines.”
It’s all part of an annual maintenance effort by PG&E to reduce power outages. This week, the utility is washing all the towers that stretch from San Luis Obispo to Interstate 5 in the Central Valley.
When most people think of power outages they think of storms or fallen tree limbs, but outages can happen any time of the year for a variety of reasons. Throughout the year, salt and dust collect on the insulators — which look like disks or balls suspended from the tower to support the electrical lines and prevent the current from flowing through the tower to the ground.
Dirt on the insulators forms sludge that, when moistened by fog or rain, drips onto the lines. This can short out the line, causing brief outages, and damage the lines and insulators.
“The annual cost for line washing is approximately $1.5 million,” Jones said. “The cost to repair equipment damage caused by this type of contamination is several times that amount. So it’s a good investment as it helps ensure a steady flow of electricity to our customers.”
The company has been washing its lines for 20 years and targets the ones that have a history of salt and dust buildup. The effort appears to be paying off.
“In 2013, we had the fewest number of outages and the shortest duration of outages in the company’s history,” Jones said.
PG&E conducts line washing from June to October. It contracts for the work with PJ Helicopters, a commercial helicopter service in Red Bluff.