A Novel Approach to Detect Symmetrical Faults Occurring During Power Swings by Using Frequency Components of Instantaneous Three-Phase Active Power

Since distance relays are prone to interpret a power swing as a three-phase fault, they should be blocked during the power swing to prevent undesired trips. On the other hand, if any fault occurs during a power swing, they should be fast and reliably unblocked. Although unblocking the relay is straightforward in the case of asymmetrical faults by using the zero-sequence and/or negative-sequence component of current, detecting symmetrical faults during a power swing is still a challenge. This paper presents a novel method for detecting symmetrical faults occurring during a power swing. Based on the damping frequency component of 50 (or 60) Hz created on instantaneous three-phase active power profile after inception of a symmetrical fault, the proposed method will be able to detect the fault in less than one power cycle. This detection method can be readily implemented, and is immune to the power swing slip frequency, fault inception time, and fault location. To test the proposed method, several power swings and faults are numerically simulated in MATLAB/SIMULNK, and the simulation results show that the proposed method is sensitive as well as reliable.