Re: Metro-North Restoration Update/Initial Findings of Feeder Failure
Over this past weekend, Con Edison successfully constructed alternate power sources to the Metro-North New Haven line, which allowed some electric trains to begin running this morning. We continue to work around-the-clock to reconnect the 138kV feeder that had been removed from service several weeks ago to accommodate Metro-North's system upgrade work. The reconnection is expected to be completed by October 7th and will provide full service to the line.
Our primary focus has been on establishing temporary feeders in Harrison, reconnecting the 138kV feeder that was taken out to accommodate Metro-North's upgrade work, and repairing the second 138kV feeder that faulted on Wednesday morning. Given this focus, we do not know with certainty the cause of the feeder failure at this time. A preliminary review indicates that the feeder fault is likely related to work that was performed to disconnect the feeder for Metro-North's upgrade work.
High-voltage transmission feeders are housed in oil-filled pipes. Removing these feeders from service is a complex process, which involves freezing the insulating oil in the pipe within a "freeze pit." These freezing operations are conducted routinely while working with high voltage transmission lines, and we perform numerous operations each year without incident.
In this case, we have confirmed that the fault is located just outside of the "freeze pit" work area. In addition, the ground surrounding the work area was found to be frozen, and this unusual condition likely contributed to the feeder failure. We cannot recall a condition of this nature developing during any of our previous freeze operations.
We will be conducting a thorough review of the cause of the feeder failure once restoration activities are completed. The review will include a thorough examination of the failed cable once it is removed from the pipe as part of the restoration process, and will focus on understanding how this incident occurred to avoid future such incidents.
We also plan to have extensive discussions with the MTA regarding contingency planning.