Modern day protection systems require easy implementation of detection and classification algorithms. Analysis of three phase voltages can impart substantial information regarding the detection and type of the faults. These signals vary with several factors like fault location, inception angle and impedance. In this study, the detection and classification of high impedance faults in a transmission line is proposed using alienation coefficients which are obtained by juxtaposing half cycles of absolute voltage signals using the moving window technique. The alienation coefficients obtained are compared with the corresponding threshold values to detect and classify the faults. Case studies undertaken by the variation of fault locations and fault inception angles have successfully validated the proposed algorithm. © 2018 IEEE.