The MBTA said yesterday it's identified the overhead power-line issues that have led to a recent spate of dead trolleys from the new Green Line Extension to the ancient tracks near Copley and on Beacon Street. The T also said it's working to keep them from happening again.
The first sudden end of service occurred Oct. 20 on the tracks between Science Park and Lechmere - leaving some riders trapped in a trolley for 90 minutes - on one of the MBTA's brand-spanking-newest lines. The T reports:
We found a broken OCS [overhead catenary system] cutout near Lechmere. Green Line Extension is a new "constant tension" system, using cables, pulleys, & weights to maintain the right amount of tension on the OCS power lines. We suspect this cutout failed prematurely & is an isolated case.
The other three failures - near Copley, also near Copley and on Beacon Street in Audubon Circle - were due to the fact that, hey, we have the nation's oldest subway system:
These were older parts in our legacy system - a "static tension" system that cannot self-adjust to tighten wires. We suspect the recent severe temperature swings caused the [wire system] to sag, wear, & break.
The T continues:
To avoid future power problems with our legacy system, we're looking into upgrading our inspection technology to new cameras & sensors to detect defects better. For now, our Power Dept is further inspecting our most sensitive Green Line sections & has replaced ~200ft of OCS wire.