GENERATOR PROTECTING RELAY

A protective relay having an operational boundary matched substantially to the output performance limit characteristics of a generator to enhance the protection. The protective relay generates a signal representative of a discriminating impedance based on measurements of the generator's terminal voltage and current. The relay utilizes two pairs of predetermined values which characterize in part the generator's output performance limit curves. Two corresponding pairs of vector signals are generated by the relay based on their respectively corresponding pairs of predetermined values and the generated discriminating impedance signal. The angles between the vector pairs are measured by the relay and are compared with predetermined angle values which also represent in part the generator's output performance limitations. Leading and lagging conditions of at least one of the vector pairs affects the selection of the predetermined angle value used in the comparison with the measured angle associated therewith. Should the results of the comparisons indicate that the measured angles are beyond their respective predetermined angle values, then the protective relay signifies that an unsafe generator operating condition exists.