No abstract

Summary Disastrous effects resulting from power system security issues have been pointed out in various blackout reports. In these reports, setting of the third zone reach being large was found to be a major reason. In addition to a fault, the apparent impedance measured by the relay can also enter the third‐zone setting for different stressed events, such as load encroachment, power swing, and voltage instability, and thus be misinterpreted as a three‐phase fault, leading to relay maloperation. To improve the functionality of the relay under such dire situations, a local end information‐based technique is proposed. The scheme uses the Teager energy‐based approach for developing an index criterion. As per the proposed method, after the entry of the impedance into the relay zone‐3 characteristic, the index is checked. If both the impedance and the index cross their respective thresholds, the disturbance event will be detected as a fault. Otherwise, it will be a no‐fault condition and undesired relay operation avoided. Reliability of the proposed technique is tested for various power system events by simulation on the New England 39‐bus, 10 machine test system.