In accordance with an R&D agreement between ABB and the University of Wroclaw, Poland, a multi-criteria protective relay based on fuzzy sets and logic has been developed for use with three-phase power transformers. Twelve criteria are used tostabilize the relay. The protection scheme features internal functions and coefficients which allow off-line self-adjustment of the relay prior to installation. Three unique procedures for the settings make the relay self-organized. Results of tests showsignificant gains in sensitivity and selectivity for the self-organized relay compared with traditional approaches to the problems of protective relaying.
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