A simple, prompt and accurate method of fault identification and classification of faults in a long transmission system is presented here using entropy analysis of post-fault three-phase current signals, measured at the sending end only. Identification of the faulted phase is imperative for restricting unwanted outage of power through the faulted phase, as well as isolation of the same in order to retain the stability of the system. Transmission line fault classification, hence, has become one of the most vital topics of research. The high-frequency transient current oscillations, appearing immediately after the fault, are analyzed in this work. Signal entropy is computed for the modified waveform of each phase using the differentiation method to highlight the edges of oscillation. Entropy measures the randomness of a signal; hence, the sudden disturbance caused in the directly affected faulted line yields much higher entropy compared to the un-faulted lines. It is further observed that the extent of disturbance in the three phases primarily depends on the type of fault caused: ground fault or non-ground fault. An attempt has been made closely to monitor the entropy levels of the three-phase currents to distinguish between each phase in terms of the level of disturbance caused in a specific class of fault using the estimated signal entropy values, thereby aiding in the development of a threshold-based fault classifier entropy signatures. The major findings of the present work are primarily twofold: 100% accuracy of classification and requirement of only (1/20)th of post-fault signal, that is, detection within 1 ms, which is commendably fast compared to several contemporary works. Besides, the variation of fault parameters, such as fault location, fault resistance and power line noise, makes the design more practically suited.
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