The electrical fire at BART’s San Leandro station last month exposed potential systemwide vulnerabilities that BART engineers are currently assessing to prevent future incidents, agency officials said Thursday.
According to a memo written Wednesday by BART’s deputy general manager, Michael Jones, to the transit agency’s governing board, the May 20 incident began when insulation around a 1,000-volt cable – used to provide power to the trackway – became so frayed that bare cable contacted the ground, creating a so-called ground fault.
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WATCH HEREAt 4:55 a.m., the ensuing power surge created arcing fire and what Jones called “cascading failures.” The fire ended up damaging the main, 34,500-volt cable that feeds power to the substation network, triggering a systemwide shutdown.
Jones had initially blamed a decades-old circuit-breaker for failing to cut off power immediately when the ground fault surge occurred. But BART engineers have since explained that the surge created by the May 20 fault wouldn’t have been substantial enough to activate the substation’s 20,000-amp breaker.
The breaker is set to handle 20,000 amps, they say, so as to safely handle the surge of power needed to start up multiple 10-car trains at once. Because the surge wouldn’t be enough to trip the breaker, it means power continued to flow for several minutes, fueling the fire.
Making matters worse for BART, the fire damaged equipment BART engineers would normally rely on to shut off the power remotely. BART officials have said they had to go to each station to turn off the power.
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In his memo to the board, Jones said engineers are currently evaluating improvements to “enhance electrical fault detection and isolation” as well as upgrading system alarms “to ensure reliability of future event detection."
“We take this event very seriously, this is a review that we want to make sure is thorough, so we cover all the bases,” said Chris Filippi, a BART spokesman. “We’re looking at several things – including components for power systems, communication cables, conduits, and that effort is in progress right now.”
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