The paper is developed in tripping mechanism for three phase supply in power system. The output of project resets after a brief interruption in event temporary fault while remains tripping condition the case of permanent fault. The electrical grid substation which supply power to the many consumers failures due to some faults which is temporary or permanent. The fault damage to the power system equipment, In India it is common, The faults is LG (Line to Ground), LL (Line to Line), 3L (Three lines) in the supply of power systems and the faults in three phase system affect the whole power system. To overcome the problem the system is make, which is sense the faults and automatic disconnect the supply of power system to avoid large scale damage in control gears in the sub-stations. This system is make using three single phase transformers and they are wired in star input, star output, and 3 transformers are connect in delta connection, in have input 220 V and output is 12 volt. In the project 555 timers are used for handle. The short duration and long time duration fault condition. A set of switch used create the LL, LG and 3L fault in low voltage side, for activating the trip mechanism. The Short time duration fault returns supply to load immediately called temporary trip while long duration result called permanent trip.