The US and Canadian governments have established a joint task force to investigate the causes of the power failure. The task force is headed by US energy secretary Spencer Abraham and Canada’s minister of natural resources Herb Dhaliwal, and the task force is supported by the Federal Energy Regulatory Commission (FERC), the Nuclear Regulatory Commission (NRC), and the North American Electric Reliability Council (NERC).

The task force reported on 12 September, presenting a timeline of events on transmission facilities of 230kV and greater and at large power plants. The task force has not yet reported on the linkages between these events or why the blackout happened. Determining these is the current focus of the task force, which will require intensive analysis of thousands of transmission line events that occurred on the 138kV grid system and on lower voltage lines over the several hours before and during the grid’s collapse, and the hundreds of events related to power plant interactions with the grid.

The analysis is based on event times derived from the “time stamp” that accompanied each data record, and recorded to the nearest second. A source of inaccuracy that is still to be reconciled, which will mainly be by cross-checking, stems from the fact that the time stamps from different areas are not necessarily synchronised.

Although the cause of the blackout and the reason for the cascade effect has not been identified, the starting point appears to have been the northeast Ohio power grid, owned by FirstEnergy. An initial NERC assessment focused on three power lines near Cleveland, Ohio. Unexplained voltage swings knocked out a generator at Eastlake plant. This was followed by a high-voltage power line tripping. A third power line, heated by the extra load it was carrying from the two previous failures, drooped into a tree and shorted. The intra-grid system allowed the blackout to feed into neighbouring Michigan, and from there up into Canada and back down into New York.

The multiple failures, which allowed the blackout to spread as far as it did, an ageing transmission infrastructure and chronic underfunding of the transmission system have been highlighted as contributory factors in the spreading of the blackout. According to the Electric Power Research Institute (EPRI), only $2.6 billion was invested in transmission in 2002, compared to $5.5 billion in 1997. Other sources have placed last year’s transmission investment levels at just $800 million. The article on page 46 of this issue summarises EPRI’s recent report on the Electricity Sector Framework for the Future.

The problem is exacerbated by the fact that while electricity demand grew by about 35% between 1988 and 1998, transmission capacity rose by just 17%. Between 1999 and 2009, electricity demand is expected to grow by 20%, with a forecasted capacity growth of just 4%.

Back in March 2003, FirstEnergy and American Electric Power had warned Ohio regulators that the spaghetti-like system of the US-Canadian grid would not be able to cope with sudden changes in electricity flows, regional power transfers, unexpected demands and extreme weather. The blackout took place during the summer heatwave, when the use of air conditioning pushes the system to the limit.

For example, New York faces annual warnings of blackouts during the peak of the summer heatwave.

The blackout came as the US Congress was in the middle of its first major rewrite of energy policy in a decade, part of which includes provisions requiring utilities’ systems to meet federal reliability standards. It is expected that consumers will bear the brunt of the recommended costs of updating the US power grid, estimated at about $50 billion. NERC president Michael Gent had warned Congress two years ago that $56 billion was needed to upgrade the larger electricity grids, but only $35 billion had been assigned for that purpose at the time of the blackout.