Transient Directional Protection Based on the Transformation of Positive Sequence Component

This paper proposes a new current mode derived by a new modal transformation technique, the alpha mode. The mode is used to detect and distinguish between internal and external faults for power line protection, based on a new transient directional comparison technique using current alone. The technique uses the symmetrical component to replace Clark or Karrenbauer transformation to decouple the three phase transient current signals. Wavelet transform is then applied to the positive sequence component to produce the modular maximum, which are subsequently used to distinguish between internal and external faults. The modular maximum of the wavelet transform for the new alpha mode have the same polarity at both ends of the line for internal faults and opposite polarity for external faults. Theoretical analysis and extensive simulation studies show that the technique is able to give correct responses for all fault types