Con Edison shined more light Monday on what caused the massive blackout on July 13 that affected 72,000 Manhattan customers.
The utility said it had conducted an extensive investigation into the relay protection system at its 65th Street substation that caused the blackout that night and “identified a flawed connection between some of the sensors and protective relays” according to a statement that noted the condition has been fixed and steps have been taken to prevent a recurrence.
The statement explained that an electrical system’s relay “detects abnormal conditions on the electrical delivery system and instantly sends signals to circuit breakers to open and isolate the problem.”
Con Ed crews temporarily took equipment out of service to simulate the event in order to diagnose the “root cause” of the blackout and reviewed 15 years of operating data, the statement said.
The utility said it has isolated relay equipment at other substations and will analyze and test each piece of equipment.
Eight days after the Manhattan blackout, 50,000 customers in Brooklyn and Queens lost power as temperatures soared over the 90-degree mark. Gov. Andrew Cuomo and Mayor Bill de Blasio have blasted ConEd for its handling of both incidents.
“I’m going to do an independent investigation with power experts that we have in the state to find out exactly what happened and why and we’ll get it done as quickly as possible,” Cuomo said on Fox 5 News Sunday.
A spokeswoman for Mayor de Blasio said hizzoner met with Con Edison’s president Friday to push for the release of the findings.
““We’re happy to see Con Edison providing New Yorkers the answers they deserve,” said mayoral spokeswoman Laura Feyer. “While the issue has since been corrected, the fact that the system did not work as designed is concerning. We are continuing to conduct our own investigation into the West Side and Brooklyn blackouts to ensure public accountability.”