Consolidated Edison of New York continues to investigate the cause of a June 27 transmission disturbance, which interrupted service to 136,700 customers (approximately 385,000 people) in the southwest Bronx and sections of the Upper East Side of Manhattan.

The company is examining data and equipment to help determine what caused the outage. In addition, engineers are examining possible links between the outage and lightning strikes in the area. It appears that there were several strikes near a transmission substation in Queens at, or near, the time of the event.

Con Edison’s initial findings show that the event occurred quickly -- in less than 10 seconds -- and involved multiple transmission lines. Protective devices operated quickly to isolate the trouble area from the rest of the system, thus preventing equipment damage and additional service impact. These devices also enabled the rapid restoration of electrical service.

The outage affected two electrical networks. The company’s transmission and distribution systems are designed to protect themselves from damage during such disturbances. These systems performed as designed; the outage did not spread to other areas.

The company was prepared for the heat wave, with several thousand employees on duty to respond to any emergency. In response to this event, Con Edison personnel operated more than 80 circuit breakers in order to restore customers in 48 minutes.