Research of fault phase selection on UHV transmission lines based on wavelet analysis

To meet the requirements of ultra-high speed protection on UHV transmission lines, this paper proposes a fault phase selection based on wavelet analysis theory, which can detect the mutations' time and size of singular signal in fault signal. Firstly, this algorithm transforms the transient fault current into model fault current to eliminate the impact of the various phases' coupling. Then modulus maximum is extracted from model fault current using discrete wavelet transform (DWT) and is treated as the criterion factors after normalizing. Finally, the relationship among criterion factors is summarized according to the characteristics of mode fault current, while constructing a new UHV fault phase selection algorithm. Through simulation studies by PSCAD and MATLAB, this method is proved that it is disturbed less by amplitude of the transient fault signal, and it has a good adaptive capacity and a strong ability for fault resistance. Also its speed is fast and accurate, so the proposed algorithm can be implemented simply and effectively.