A new blocking scheme for distance protection during power swings

This paper presents a new and fast algorithm to prevent distance relay mal-operation during power swings. The algorithm blocks the relay tripping signals during power swing and unblocks the signals if a fault occurs during power swing. The proposed blocking scheme for distance protection incorporates an additional criterion into the conventional relay which is based on the derivative of the line reactive power as seen by the relay. This technique overcomes the shortcoming of conventional power swing detector (PSD) by removing the pre-defined R-X diagram. The conventional PSD has the difficulty in obtaining the timer setting at pre-defined R-X diagram due to varying cycle of power swings. To illustrate the effectiveness of the proposed algorithm, simulations were carried out on the IEEE 39 bus test system using the PSS/E software. Test results show the effectiveness of the proposed scheme in blocking the relay's false trip signals during power swing.