At a Wednesday morning state Senate subcommittee hearing, representatives from the California’s largest utility companies detailed how they are addressing public safety hazards associated with downed power lines, underground infrastructure and other risk factors.
According to data provided by the California Public Utilities Commission (CPUC), during the past decade about a dozen people (utility workers and the public combined) on average have been killed each year due to electric incidents in the service area of PG&E, Southern California Edison and San Diego Gas & Electric, which together serve 11.5 million customers.
Pat Hogan, vice president of asset management for Pacific Gas and Electric Co., said the utility is taking a variety of measures to address the safety of underground components, such as conducting detailed annual inspections, pursuing new transformer designs, and deploying software and hardware that monitors performance of the underground network in real time. PG&E also is using infrared to inspect vaults to find hot spots on cables that could indicate a failure point, he said.
In 2005 a woman was badly burned when an underground transformer exploded in an underground vault while she was walking in the San Francisco’s financial district, a tragic accident that Hogan said PG&E never wants to happen again.
"When an underground component fails. Because it’s in a confined space, it can produce hot gases that can rapidly increase pressure, and this increased pressure can displace manholes," Hogan said.
In its service area PG&E has installed 2,500 manhole covers that lock and lift, allowing gases to vent, he added.
Don Neal, director of corporate environmental, health and safety for Southern California Edison, said it’s a big job to detect downed power lines in SCE’s service area amid 1.5 million power poles, 725,000 transformers and 90,000 miles of lines. One area he said the utility is looking at is high-impetus faults.
"Due to the high impetus of some events, such as when conductors fall on dry asphalt, the fault current is significantly lower than minimum detection setting of a relay, which prevents the fault from being detected and the line to remain live," Neal explained. The utility been working with major relay manufacturers on new detection technologies for this type of fault and has completed four pilot installations, he added.
Neal noted that some electric incidents are started by "outside agencies," such as Mylar balloons, which can come in contact with a power line and cause a short.
"Mylar balloons are a lot more prevalent in causing these system failures than I would’ve ever believed until I got into this business," Neal said.
Elizaveta Malashenko, deputy director of the Office of Utility Safety and Reliability within the California Public Utilities Commission, said smart meters, conditions-based monitoring of smart meters, line sensors, distribution automation and other technologies could alter the landscape.
"I think it’s really something that can drastically change how we approach some of the safety issues that have been in the industry for a long time," she said.
State Sen. Jerry Hill (D-San Mateo), chair of the Senate Energy, Utilities and Communication Subcommittee on Gas and Electric Infrastructure Safety, said he hopes California’s electric utilities can do a better job of collecting and coordinating their safety data.
"With the wave of impending smartness coming toward us, it should be surprising we know relatively little about the safety of that grid," Hill said. "The states don’t collect much data and what they do isn’t published. Industry collects some data across state lines but it’s unclear how much communication occurs among the nation’s utilities."
