All of TriMet's MAX light rail trains were idled Monday, after a power outage on Portland's Steel Bridge.
A brand new surge arrestor on the Steel Bridge was the start of the MAX problems. It failed, and caused the outage. TriMet spokeswoman Roberta Altstadt says it's like when a surge protector in a home fails.
"It's a part of the electrical system that allows the power to go through to the overhead wires," Altstadt says. "So when that fails, the power can't get there."
When a surge arrestor goes out, the only way TriMet can fix it is to replace it. The outage can spread because the power load shifts to nearby substations.
Monday's outage spread downtown and to the Gateway substation. Altstadt says the outage was an anomaly. TriMet is investing $53 million this year to replace old equipment and make the MAX system more reliable.
This story originally appeared on Oregon Public Broadcasting.