A multi-criteria fuzzy logic transformer protection

The paper describes a multi-criteria self-organized fuzzy logic based protective relay for three-phase power transformers. The employed protection criteria and the overall relay organization are presented as well as the novel algorithms for off-line pre-installation self-setting of the relay. These algorithms are based on statistical information obtained by mass-simulation using ATP-EMTP package and enable a kind of learning phase similar to that known from artificial neural network applications to power system protection. The example and results of testing demonstrate high stability and sensitivity of the presented relay which operates with average tripping time below half a cycle. Robustness of the relay has been also confirmed.