Substation is a power transmission channel (electrical) system that has an important role in its operation. Therefore, the design of a power system requires very careful consideration and consider the conditions in the field that may occur interference from external factors in internal factors in a power system can be minimized with the results of the analysis. In the electric power system does not close the possibility of interference from outside or from within. These interruptions include damage to the generator, broken wire, interconnect simgkat due to lightning strikes. Therefore, in the power system has a safety equipment (protection system) to secure the equipment from interference and avoid from damage. With the protection system does not inhibit the distribution of electricity to the load (consumer). From the various disturbances that occur can be in the analysis of disturbances and can be determined system of protection used in power system equipment such as determine the specification raiting circuit breaker (CB), switchgear, and determining the quantities to determine a relay work or setting a relay for protection equipment. Electrical power system equipment, among others: transformer, network generator some power system equipment is minmalisir against interference at komdisi abnormal operation of the system itself.