BART takes steps to end power surges

Riders and the Warm Springs BART station on first day of service, Saturday, March 25, 2017 in Fremont, CA. Riders and the Warm Springs BART station on first day of service, Saturday, March 25, 2017 in Fremont, CA. Photo: Eric Kayne, Special To The Chronicle Photo: Eric Kayne, Special To The Chronicle Image 1 of / 22 Caption Close BART takes steps to end power surges 1 / 22 Back to Gallery

BART engineers hope to avoid a recurrence of mysterious power-surge problems that forced dozens of BART rail cars out of service on the far end of the Pittsburg/Bay Point line last year and again on Friday by equipping rail maintenance vehicles with powerful magnets, temporarily halting noise-reducing rail grinding and lowering the amount of power to trains in the area.

Voltage spikes Friday knocked 22 trains out of service on a troublesome stretch between the North Concord and Pittsburg/Bay Point stations. The surges forced BART to stop direct service and force riders onto shuttle trains between the stations through the evening commute.

Engineers resolved the problem late Friday night by changing the way BART delivers power to trains traveling the uphill stretch of tracks, said Jim Allison, a BART spokesman. At the same time, power to the trains was reduced by 5 percent.

While Friday’s problems differed slightly from the mysterious power surges in the same area that knocked more than 50 cars out of service in March and April 2016, BART officials determined the causes were related.

A team of experts from inside and outside BART studied the 2016 voltage spikes for months before determining they were likely caused by metallic particles. The particles produced by rail grinding designed to reduce noise were clinging to the undersides of rail cars, interacting with ground moisture and high levels of power to cause arcing, or electrical flashes.

Since then, BART has used vacuum trucks to trail rail-grinding machines and suck up the particles inside tunnels. Engineers thought wind and rain were washing away particles from rail grinding on ground-level tracks, sweeping them into the gravel ballast underneath. But that was apparently not the case between North Concord and Pittsburg/Bay Point, where crews have been grinding rails four nights a week for the past 3½ weeks, Allison said.

BART plans to outfit some rail maintenance vehicles with powerful magnets to pick up the metallic particles on that stretch and possibly elsewhere, but not from the gravel. The magnets are expected to be in service in about a month. Until then, BART has halted rail grinding in the area.

Engineers have also reduced power to trains traveling between the two stations. Trains climbing the hill on rails in the median of Highway 4 use more power than anywhere else in the BART system, Allison said, and that’s believed to contribute to the arcing. Power has been reduced by about 5 percent, he said, but it’s not expected to slow trains or be noticeable to passengers.

While the power problems had no direct affect on Monday’s morning commute, they did cause BART to run shorter trains. To run trains with as many cars as it has promised its riders, BART needs 595 rail cars, a goal it has been unable to attain recently. On Monday morning, with its shortage worsened by Friday’s electrical troubles, just 568 were available.

“We did have some trains that were short by a car,” Allison said.

He was unable to say how long it would take to get all the damaged cars back in service.

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com Twitter: @ctuan