The power outage that knocked out train service on Metro-North’s New Haven line last month was caused by workers using liquid nitrogen to do repairs — and authorities are trying to figure out what went wrong.
Workers had taken a power feeder line out of service in Mount Vernon on Sept. 25 in order to upgrade it, and used liquid nitrogen to freeze the oil in the spot where they were working, according to Con Edison.
Only in this instance, the ground in a nearby spot also froze, causing the power outage on the cable that powered the New Haven line.
“That’s a phenomenon we’ve never seen before,” said spokesman Michael Clenendin. “It’s very, very unusual. We will find out the cause.”
He noted that Con Edison does about 20 freeze operations a year and has been doing so for decades.
The utility company plans to analyze the damaged cable, as well as the area around it to figure out what happened.
Full service on the New Haven line was restored Monday, after several tests were done at a new electrical substation in Mount Vernon.
The customers who were affected by the outage can seek a credit for future weekly and monthly ticket purchases.
The state’s Public Service Commission, which regulates utilities, is also investigating the outage.