A Quick Trip To The Islands

More commentary on the Blackout

Stressed? Over-worked? Need to get a way from it all? When the going gets tough on the transmission grid, sometimes a quick trip to the islands is just what is needed.

One way of making the grid work better is to figure out how it can fall apart more gracefully. The ability of a subregion to cut itself off from the surrounding grid ? islanding ? can help limit the cascading failures that constitute wide-spread blackouts. This was one of the lessons drawn from the 1965 blackout.

But islanding can cause problems of its own, too, if not done well. If the subregion that separates is itself not already in approximate balance between generation and load, it may fail anyway. In addition, the system left behind by the islanders may become more difficult to manage.

If you follow the details of the cascade in Chapter 6 of the Task Force final report, you learn that at 4:10:39 PM tripping of protective relays isolated Cleveland and Toledo from the rest of the grid. The island was unstable because there was insufficient generation inside the island, the island dropped load but couldn?t stabilize and blacked out. At the same time, Detroit suddenly had a lot of excess power because the Cleveland and Toledo load separated from the system, and this excess power bounced back through the system tripping additional relays and leading to the separation of much of the Northeastern U.S. and Eastern Canada from the rest of the Eastern interconnection.

On the other hand, most of New England and the Maritimes separated from the rest of the grid and kept operating, as did small regions in New York, Ontario, and Quebec.

The islanding was result of individual relay trips, not coordinated responses, and the results didn?t do much to stabilize the system. Research into dynamic islanding has looked for ways for the system to fall apart more gracefully. The idea behind dynamic islanding is that the system could be intentionally separated into self-sustaining parts ? based upon current system operating conditions ? rather than allowing haphazard islanding to result from individual equipment trips. (Research was done at EPRI; Some of the works is carried forward by CEIDS.)

The exploration of dynamic islanding is just part of the process of understanding how the transmission grid is changing. The partial restructuring of the industry that we have gone through over the past few years has lead to changes in the use of the grid. In the regions in which restructuring has most advanced, use of generation and transmission resources are carefully coordinated so as to avoid placing the system at risk. In principle, the markets and operating systems that the Midwest ISO is putting into place should gain them similar protection once their markets start up. But much of the country operates outside of such regional operations and even within these regions, operating reliably requires a constant effort to understand the more active, vibrant transmission grid we now have.

Interesting research on cascading in networks has been conducted by Benjamin Carreras, Ian Dobson and others. Statistical examination of blackout frequency showed that larger blackouts were more frequent that expected. After some additional research, one of their surprising insights was that local efforts to prevent small blackouts may cause the system to become more susceptible to big blackouts. (Several papers here. Some of this work supported by DOE?s current transmission research effort.)

Current contingency planning practices will also need to change to keep up with the times. The blackout report describes the standard N-1 planning criteria: seek to operate the system so that it could the survive the loss of any single component. Some parts of the system are operated under more stringent N-2 criteria. These criteria have been designed primarily to guard the system against component failure, but the prospect of terrorist or other malicious acts suggests the need for some new thinking.

Component failures are often modelled as more-or-less random events, but a planned attack would produce a quite different profile of component failures. Likely, no amount of building up additional supply-side generation and transmission reserves will get us the level of reliability that we want from our bulk power grid. ?Hardening the target? by increasing physical measures at power plants and transmission stations will only provide modest improvements in security against attack. The grid is by nature exposed to the world. The grid needs to become smarter in responding to changing operating conditions.

The blackout report did make some related recommendations. It seeks additional support for research, and suggests a number of physical and cyber security changes.

As we take up the recommendations, let us ensure we are developing ways of working with our increasingly dynamic grid in the face of changing uses and newly apparent risks, not trying to go backward. Part of the answer is to reach out to the demand-side, through approaches like those we discussed Tuesday. Another part of the solution is through better understanding of complex networks.

And when all else fails, and it is time to head to the islands, let?s figure out how to do that intelligently, too.