Abstract
The Norwegian system operator plans to change from (N-1) to a more flexible cost-based security criterion. The approach is illustrated using a simple example and then compared with alternative decision paradigms. The comparison shows how different paradigms may change ranking of operating alternatives and that the new cost-based criterion still tends to favor alternatives close to (N-1), provided application of a penalty factor giving additional and significant weight on interruption costs. Copyright © 2007 John Wiley & Sons, Ltd.