Circuit breaker and relays are being utilized for secure, reliable and convenient operation of power system. The over current protection relay is widely used in the power system for protection of short circuit or wrong setting of system to the pre-specified value. Erroneous setting of over current relay in the power system it is difficult to send the trip signal. So it is connected carefully in the power system. Therefore it is important to accredit the setting of power protection equipment. The paper represents the modeling of over current relay in MATLAB/SIMULINK. The over current relay has the types of instantaneous, definite time, inverse time and inverse definite minimum time (IDMT) according to the time characteristics. This paper most important feature is the comparison of times between ideal & calculated results of over current relay. To make the protection system of transmission line by the circuit breaker and over current relay in MATLAB/SIMULINK. To proper transmit the electric power from sending end to receiving end without suffering from any difficulty and dangerous condition. Implementation of over current relay and testing of circuit breaker & over current relay are using in MATLAB software. And show the result of operating & fault current and also trip signal time of the over current .