In this paper a novel algorithm for unblocking distance relays during power swing is described. The algorithm is based on the participation factors drawn from a variance-covariance matrix, which is built by incremental currents after a fault takes place. By modal analysis techniques, the eigenvalues and participation factors are calculated and they are used for identifying a three-phase fault condition under power swing conditions. The algorithm's performance is verified through simulation by electromagnetic transient software under different conditions. The analyzed scenarios demonstrate that the proposal algorithm correctly identifies a fault when the distance relay is blocked during a power swing.