Blackout Watch

System Power Outages

Author: Clare Duffy, ESBI, Ireland

Analysis of system power outages can help us learn and avoiding similar events in the future. If you have information on any blackouts, please e-mail to

2 February 2011, Texas, USA
The Texas power grid operator imposed rare rolling blackouts as frigid weather swept across the state, leaving nearly 3 million homes temporarily without electricity. When the cold snap caused 7,000 MW of power plants to shut down, the grid operator declared an energy emergency and called on state energy suppliers to cut about 4,000 MW of power demand (equal to about 2.9 million homes). The grid operator reduced that call to about 3,000 MW by mid-morning as some generation returned to service.

2 February 2011, Sydney, Australia
Roughly 12,000 homes and businesses were left without power in the city’s western areas because of a fault in an underground supply cable. Power outages continued for several days in some areas as demand hit a record 14,744 MW during summer heat. Energy Australia offered $100 compensation for customers affected for more than six hours.

3 February 2011, Recife, Brazil
A defective circuit at an electrical substation was blamed for a widespread blackout, according to Brazil’s Mines and Energy Minister Lobao. The defect occurred at the Luiz Gonzaga substation, which feeds high-transmission lines leading to other energy suppliers, causing the failure to ripple across the region. It began late in the evening and continued until the following morning. Estimates put the number of residents affected at nearly 10 million.

22 March 2011, Berkeley, California
Most of downtown and the area around the University of California lost power around 11:15a.m., causing headaches for commuters. Area trains had to pass Berkeley stations that were without power for nearly two hours. Pacific Gas & Electric said that by 1p.m. power had been restored to most of the 27,000 customers that were affected. No cause has yet been announced for the outage.

5 April 2010, Hyderabad, India
Several areas experienced unscheduled blackouts ranging in duration from thirty minutes up to two hours. For units engaged in continuous processing, uninterrupted supply was being ensured with a rider that consumption should be capped at 70% of the connected load.  While the unrestricted demand for CPDCL (Central Power Distribution Company of A.P. Limited) scaled up to 5,300 MW, what the company was able to supply was only 4,700 megawatts.

7 April 2011, Caracas, Venezuela
A major blackout struck most of the country, including the Caracas metro area just before rush hour. The city’s transit system ground to a halt, forcing thousands of commuters into the streets. It is believed the cause may have been a forest fire that caused the failure of a high voltage cable and affected 6,000 MW of capacity. Power was restored in most areas soon after, but many regions would be cut off for brief periods during the evening to ration energy as the system stabilized.

26 April 2011, Green Bay, Wisconsin
The western portion of the city was hit by a blackout after problems occurred on a nearby transmission line. Wisconsin Public Service was able to quickly restore power to most of the estimated 12,000 customers affected, however several area schools closed for the day and sent their students home.

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