In this paper a new numerical algorithm for medium voltage overhead line protection and autoreclosure is presented. It is based on one terminal data processing and it is derived in the time domain. In the algorithm, the fault location and fault nature (arcing or arcless fault) are estimated using the linear least error squares estimation technique. An arc occurring on the fault point during arcing faults on overhead lines is included in the consideration of the problem. Additionally, by introducing the pre-fault load current in the existing model, better algorithm performances are achieved. The algorithm is derived for the case of a three-phase symmetrical fault. The computer simulation results of the algorithm testing are presented and, in particular, the algorithm sensitivity to arc elongation effects and processing of the signals in the presence of harmonics is tested and analysed.