Abstract: This paper proposes a symmetrical short circuit current calculation algorithm in power systems transmission lines. The method consists of adding a fictitious node in the power system, located at the point where it is required to calculate the fault in the transmission line, and is defined as a percentage taking as a reference the line sending node. Once the fault point is specified, the systematic fault analysis of the power system is carried out using the Z-bar matrix. The algorithms reliability and accuracy are demonstrated through a case study with a 5-node test power system and a real equivalent system of 39 nodes. The results of the study cases show that the proposed algorithm is reliable and accurate for calculating or simulating symmetrical faults in power systems transmission lines.