Mitigation and wavelet analysis for power swing in IEEE 9 bus system

Power oscillations occur in a transmission line due to various transients affect distance relay characteristics and may result in relay mal-operation. This paper presents new approach to damp out the power oscillation as early as possible by using power system stabilizer. Due to early damp out oscillations, no much variation is seen in the measured apparent impedance at relay location and it could not enter the relay tripping zone and prevent the distance relay mal-operation during power swing. To explain the affectivity of the proposed scheme, the simulation was conducted on IEEE 9 bus system using PSCAD/EMTDC software. The results shows comparison between change in load angle, speed and power swing with and without PSS when 3 phase fault is created in bus number 5 of IEEE 9 bus system. In addition to that multi-resolution based haar wavelet transform is used to decompose the analyzed signal into different frequency band and analysis the energy level in both cases. The technique includes separation and reformation of the faulted signal to extract the low - frequency component of the signals. With this new feature, make numerical relay more effective and more reliable in case of power swing.