Increasing frequency of black-outs in the U.S.

       

The trend over recent decades is clear

The frequency of large power blackouts in the U.S. has not decreased. In fact, there has even been a slight increase during the period from 1984 to 2006. That is the main conclusion of a working paper, published last January, by the Carnegie Mellon Electricity Industry Centre, based on analysing data from the North-American Electric Reliability Council (NERC). This increase in blackouts occurred in spite of substantial investments by the electricity industry to improve system-wide reliability.

Although the data alone do not provide enough information to deduce the exact causes, the authors discuss four plausible explanations:

1. The restructuring of the electricity industry in the U.S., starting with FERC Order 888. This restructuring allowed open access to transmission capacity, resulting in additional use of transmission resources for long distance transfers. This might have decreased availability of the lines and in this way increased blackout risk.
2. Inadequate investments in transmission network infrastructure. Although investments in the transmission grid have increased fairly steadily since 1999, they are still insufficient. This is borne out by the fact that availability of transmission capacity continues to decrease. The authors of the paper stress that building new lines is not the only way of enhancing the availability of the grid. Other measures are also possible. These include such things as composite conductors to increase thermal ratings of lines and phase-shifting transformers to relieve bottleneck constraints.
3. Insufficient system-wide management of the electricity network. A systems approach to risk mitigation is lacking, as are enforceable reliability rules.
4. Poor alignment of protective systems design. The design of protection systems in electrical power networks is poorly aligned with the main objective of the system: delivering energy to customers. It is mainly designed to minimise equipment damage, which may often result in sub-optimal performance with respect to reliability of supply.

Those issues are not restricted just to the situation in North America. In fact, they sound all too familiar to European energy professionals.

Reference

Article 'Trends in the History of Large Blackouts in the United States' by The Carnegie Mellon Electricity Industry Center.