Population development is one factor that influences the amount of electricity use capacity. So that the distribution of electrical energy from the substation must also be adequate and ensure the safety of consumers. The greater the electrical energy load will cause an increase in the presentation of the disturbance so that the transformer must be protected from overloading or interference from other factors. In this case, a reliable protection system is needed. Coordination of the protection system Overcurrent Relay (OCR) and Ground Fault Relay (GFR) is needed so that when there is a short circuit or one phase interference to the ground, the interference does not extend to the system or damage the system equipment, so the process of distributing electrical energy is still running well. This study discusses the analysis and evaluation of the protection system at 150 kV Wirobrajan substation. This study also uses ETAP 12.6 Software as a simulator. This study uses a manual calculation method that is done in detail to get good evaluation results. After obtaining a good calculation result, the calculation results are simulated on ETAP software to find out whether the protection system works well or vice versa. If the results obtained are not good, the calculation is done manually again.