Arrangement and method for protecting an electric power system

The present invention is concerned with the protection of an electric power system (1) by means of protective relays (2, 2', 2") comprising each a phasor measurement facility (20) for measuring synchronized current and/or voltage phasor values at a location (11, 11', 11") of the respective protective relay (2, 2', 2") as well as a data communication module (21) for transmitting and/or receiving measured phasor values to and/or from other protective relays via a communication link (3). A system protection facility (23) for performing a plurality of protection functions (Line differential protection (LDP), Line thermal monitoring (LTM), Phase angle monitoring (PAM), Power Oscillation Monitoring (POM), Voltage stability monitoring (VSM)) based on synchronized phasor values measured at the locations (11", 11') of two distinct protective relays (2", 2') is integrated in one of the protective relays (2", 2').