Abstract
In this paper rough-set-based data mining strategy is formulated to analyze the relay trip assertion, impedance element activation, and fault characteristics of a distance relay decision system. Using rough set theory, the uncertainty and vagueness in the relay event report can be resolved using the concepts of discernibility, elementary sets and set approximations. Nowadays protection engineers are suffering from very complex implementations of protection system analysis due to massive quantities of data coming from diverse points of intelligent electronic devices. To help the protection engineers deal with the crucial necessity and benefit of protection system analysis without the arduous handling of overwhelming data, using recorded data resident in digital protective relays alone in an automated approach called knowledge discovery in database is certainly of an immense help. The rough set approach adopts an individually-event-based paradigm in which detailed time tracking analysis of relay operation has been successfully performed.