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.
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