Power ‘protector’ was culprit: Con Ed

A system meant to prevent electric outages helped cause the big one that hit Manhattan over the weekend, Con Edison said.

It began when a 13,000-volt distribution cable failed at W. 64th St. and West End Ave. about 6:47 p.m. Saturday, the company said in a statement on Monday.

But the cable failure was just the beginning of the problem.

A series of relay switches about a block away, at the company’s W.

65th St. substation, should have automatically diverted power around the failed cable, the company says. Those relays failed. “While the cable fault was an initiating event, the customer outages were the result of the failure of the protective relay systems,” Con Ed explained in a statement.

The failure cascaded through the company’s cables and switching systems to a substation at W. 49th St. — where relays prevented the outage from spreading further.

But by then the damage was done — power was gone on a swath of Manhattan’s West Side, roughly from W. 72nd St. south to W. 30th St. The approximate eastern boundary of the blackout was Fifth Ave.

Con Ed initially believed the failure of the 13,000-volt cable at W. 64th St. was “unrelated to the transmission disturbance” — but further investigation proved that it was the blackout’s triggering event, the company said.

More than half the 72,000 Con Ed customers affected by the blackout had power back in about three hours, the company said. Everyone affected had power back by around midnight.

Mayor de Blasio — who was pursuing his long-shot presidential candidacy in Iowa when the blackout hit — challenged the judgment of the company’s engineers.

“I am troubled that one of the few factors Con Edison initially ruled out, the 13,000-volt cable, has been determined to be the catalyst of the outage,” de Blasio said.

“Thankfully, as a result of the quick work of our first responders, no one was injured and there was no spike in crime in the five hours the incident lasted.”