The development of technology today, the electricity needs must also be fulfilled very well. The more the number of population developments in an area, the electrical energy needs will also increase, so that the electricity used is also increasing along with the increase in the load of electrical energy. When the load of electrical energy continues to increase, it will also have an impact on the workability of the transformer. Therefore the transformer used must be protected from a variety of disturbances, one of which is excessive load interference. Over Current Relay (OCR) and Ground Fault Relay (GFR) is a relay that works to detect excess current that passes through the system and gives an order to the CB (breaker) for a trip that aims to provide protection to the power transformer from existing interference. This study will analyze the ability of the Over Current Relay (OCR) and Ground Fault Relay (GFR) systems in the 150 kV Gejayan Substation and use ETAP software as a simulation media. The method used in this study is the search for data needed in the 150 kV Gejayan Substation. The data obtained is used for mathematical calculations. The results obtained from the calculation showed that the largest short circuit current is 3 phase short circuit current at the point of disturbance 0% for 12523.86 Ampere, 2 phase short circuit current at the point of fault location 0% at 10845.98 Ampere and 1 phase short circuit current to the ground at the point of disturbance 0% at 3415.29 Ampere. From the data installed with the calculation data there are differences or insignificant differences.