Con Ed identifies ‘flawed connection’ as cause of Manhattan’s major blackout

Two weeks after a blackout crippled part of Manhattan for five hours, Con Edison has identified a “flawed connection” within its system as the culprit behind the July 13 outage.

An issue with the utility company’s relay protection system, which in theory should trigger a circuit breaker to prevent equipment from frying the system, led to the outage. A damaged 13,000-volt distribution cable at West 64th Street and West End Avenue was the “initiating event” that systems did not kick in to isolate, according to Con Ed’s preliminary findings.

On Monday, the utility giant released new details on the incident, explaining that the relay system did not work as expected because of “a flawed connection between some of the sensors and protective relays at the substation,” the company said in a statement. The defective connection served as the “root cause” of the outage and has been corrected, according to Con Ed.

Since the outage that left some 72,000 Con Ed customers in the dark, the company’s engineers have poured over the system and reviewed 15 years of operating data. Equipment was taken out of service at the 65th Street substation to conduct diagnostic testing, which allowed crews to simulate the incident. “Preventive measures” to isolate similar outage-inducing relay equipment were also taken, according to the company. That equipment will be tested and analyzed before it is put back into service.

Yet the news comes as little comfort as outages continue to pound the city this summer. Eight days after the Manhattan blackout, 50,000 customers in Brooklyn and Queens lost power as the mercury rose to above 90 degrees amid a brutal heat wave. More than 30,000 customers had their juice deliberately cut by Con Ed “thereby avoiding a much longer outage,” Con Ed spokesperson Allen Drury told Curbed at the time.

But thousands were forced to go days without power as crews scrambled to restore service. To complicate matters, the utility company is five years late delivering a state-mandated study that could have helped Con Ed better prepare for the heat wave-triggered outages.

Severe thunderstorm only made the situation worse, knocking out power for an additional 11,000 customers just after the heat wave. Whipping winds launched debris that downed power lines and damaged utility poles. Some New Yorkers who had their power restored only hours earlier lost it again during the powerful storms.

Elected officials were quick to decry the debacle. Mayor Bill de Blasio said he was “extremely disappointed” in the utility company and Gov. Andrew Cuomo chided Con Ed, charging that “they should have been better prepared—period.”

City and state investigations of the blackouts are ongoing.