Using relays for unbalanced faults on generators

THE REVISION OF THE STANDARD describing “Short-Circuit Requirements” for synchronous rotating machines is of considerable interest to the relay engineer. The quantitative statement of current-time capability of the generator makes available a basis for coordination of system and machine relaying on unbalanced faults. The permissible time duration of unbalanced faults is expressed as a variable based on if I2²t being constant, where I2 is the negative-sequence component of generator armature current and t is the time in seconds.