The electric power system consists of generation, transmission, and distribution components. In the process of conducting electrical energy in the transmission, disturbances can appear and one of them occurs on the power transformer. The protection system is needed to identification disturbances and decreases the damage problems by restricting the disturbed area. The protection of power transformers is using differential relays. The basic principle of this relay is Kirchoff's law where the inrush current equals the outflow. This study discusses comparing theoretical differential relay settings with the actual differential relay settings data on the Transformer IV 60 MVA Kentungan substation, also simulate it with ETAP 12.6 software. The method used by the writer is taking raw data by researching the 150-kV substation, after that all the component data are calculated manually and simulated with ETAP 12.6 software. The setting current based on theoretical calculations is 0.29 A, whereas the actual setting differential relay is 0.3 A. In the differential relay characteristic test, the differential current read on R and S phase is 0.342 A and 0.338 A in phase T. The differential relay will work if the currents that flow is greater than the current setting and if the disturbances occur in the safety area. After that, the relay will notify the circuit breaker to trip.