Appendix E

Examples of Large Outages

NORTHEAST BLACKOUT AFFECTING UNITED STATES AND SOUTHEAST CANADA (AUGUST 13, 2003)

Pre-Event

Due to the minimal amount of warning time before this event, no significant preparations were taken.

Event

High electricity demand in central Ohio combined with scheduled maintenance of several generators resulted in low voltage around the Cleveland-Akron area. Computer and alarm systems failed to warn operators due to software bugs in both the power company’s and regulating authority’s computer systems. Three 345 kV lines feeding central Ohio tripped due to contact with trees. Cascading failures resulted throughout the region as lower-voltage lines attempted and failed to take on the redistributed load from tripped lines. The blackout affected at least 50,000,000 customers, caused a loss of 70,000 MW, cost $4–10 billion, and contributed to 11 deaths.

Recovery

Most areas were restored to full power within hours, but some areas in the United States were without power for 4 days. Parts of Ontario experienced rotating blackouts for up to 2 weeks. Physical damage was limited, making recovery much faster than other types of events.

Lessons Learned

Improvements in system protection to slow or limit cascading failures should be made. Improvements in operator training, emergency response plans, communication between reliability coordinators and utilities, and sensor usage should also be made. Managing and pruning of vegetation and vegetation-caused bulk incidents should be reported to the North American Electric Reliability Corporation (NERC) and regional reliability coordinators (NERC, 2004).

WEST COAST BLACKOUT (AUGUST 10, 1996)

Pre-Event

Due to the minimal amount of warning time before this event, no significant preparations were taken.

Event

Heavy loading on 500 kV transmission lines and the western interconnect system was caused by good hydro conditions in the northwest region and high demand in California resulting from high summer temperatures. The 500 kV Big Eddy-Ostrander line arced to a tree, followed by four more 500 kV lines over 100 minutes. Several smaller lines also arced and closed. Systems protections removed 1,180 MW of generation from the system, creating an unstable power oscillation and ultimately causing islanding of the Western Electricity Coordinating Council into four distinct islands: Island 1, Alberta, Canada; Island 2, Colorado to British Columbia; Island 3, Central to Northern California; and Island 4, Southern California to New Mexico to Northern Mexico. The outage affected approximately 7,500,000 customers and caused a loss of 33,024 MW.

Recovery

Physical damage was limited, making recovery much faster than other types of events. Islands 1 and 2 had power restored within 2 hours. Island 3 was restored within 9 hours. Island 4 was restored within 6 hours.

Lessons Learned

Limiting certain high-voltage lines would prevent cascading failures. Insuring coordination between power producers and transmission operators is imperative (NERC, 2002).

GEOMAGNETIC DISTURBANCE AFFECTING EASTERN CANADA (MARCH 13, 1989)

Pre-Event

Due to the small amount of warning time before this event, no significant preparations were taken. However, forecasts for solar storm events may enable preparation in the future.

Event

At 2:45 a.m., a solar magnetic storm resulting from a solar flare tripped five lines in Eastern Canada by inducing a quasi-direct current. The land surrounding the Hudson Bay rests on an igneous rock shield, making the region more susceptible to ground-induced currents that result from solar storms. Higher latitudes also determine a location’s magnetic storm vulnerability. The outage affected approximately 6,000,000 customers and caused a loss of 19,400 MW.

Recovery

Forty-eight percent of power was restored after 5 hours. Eighty-three percent of power was restored after 9 hours. Some strategic equipment and two major step-up transformers were damaged and required repair due to overvoltage.

Lessons Learned

NERC urged the National Oceanic and Atmospheric Administration for the capabilities and coordination for at least 1 hour of notice of solar storms. Forecasting remains less precise compared to meteorological events but still has potential to give minutes to hours of warning to grid operators for the approach of strong solar storms. Current standards require systems to withstand benchmark geomagnetic disturbance events, particularly to prevent high-voltage transformers from overheating (NERC, 1989).

ICE STORM AFFECTING SOUTHERN CANADA AND THE NORTHEAST UNITED STATES (JANUARY 10, 1998)

Pre-Event

The severity of the ice storm was poorly predicted since icing conditions depend critically on the vertical atmospheric temperature profile. As a result, officials did not make any significant preparations for this event.

Event

During a series of severe ice storms beginning on January 5, heavy ice and snow loads caused the destruction of trees and high-voltage towers. Thirty thousand wooden utility poles collapsed, leaving millions without power. Two major generating stations were disconnected from the rest of the grid due to line tripping, causing the area to blackout. The bulk transmission grid remained mostly intact, keeping the outage from spreading too far outside of the Québec area. The outage affected 2,800,000 customers and caused a loss of 18,500 MW.

Recovery

Hundreds of utility crews from outside the area were brought in, along with 16,000 Canadian military personnel, making this the largest deployment of Canadian military since the Korean War. American military also assisted in recovery efforts. Northern New York and New England had their power returned within 3 weeks. Québec had its power back online within 4 weeks.

Lessons Learned

Disruptions of telephone, cellular, and fiber-optic cables made communication difficult. The most reliable means of communications were found to be the utility-owned and operated microwave and mobile radio systems. More accurate temperature profiling and precautions around temperatures where ice storms are possible would be beneficial for preparing for any outage that results from these types of storms. Building towers and lines to withstand greater weights from icing would also result in greater resilience (NERC, 2001).

HURRICANE SANDY AFFECTING THE NORTHEAST UNITED STATES (OCTOBER 29, 2012)

Pre-Event

Unlike unexpected cascading failures or solar storms, hurricanes typically offer days of warning before outages occur. In the days leading up to landfall, extensive communication was made between utilities and generating facilities to prepare for abnormal operation, including preparing black-start units with enough fuel for emergency use. Additional field operation crews were made available for response. Sandbags and other barriers were put around vulnerable substations. In the minutes and hours leading up to outages, flood-prone areas were de-energized.

Event

Superstorm Sandy made landfall over New Jersey, New York, and the northern mid-Atlantic with wind speeds of

about 80 mph at landfall and a storm surge that flooded low-lying assets, causing more than 260 transmission trips and loss of roughly 20,000 MW of generation capacity. High winds and flooding were the major causes of outages, with some snow and icing contributing as well. More than 5,770,000 customers were affected.

Recovery

Ninety-five percent of customers’ power was restored between November 1, 2012, and November 9, 2012.

Lessons Learned

Pre-staging equipment for recovery and de-energizing facilities in flood-prone areas can mitigate losses and hasten recovery. Implementing flood-protected facilities that include water-tight doors and barricades would prevent some stations from tripping (NERC, 2014).

REFERENCES