This paper presents a real-time condition assessment procedure for high-voltage circuit breakers (CBs). The simulation of CBs can be fulfilled using the existing arc models. These models can be used to characterize the transient behavior of CB after each operation. The transient signals originated by electric arcs contain several harmonics. Arc voltages can be effectively utilized to detect anomalies of CBs. Here, the total harmonic distortion (THD) index is considered in diagnosing the CB operating mechanism. The CB modeling and simulation are performed in the electro-magnetic transient program (EMTP) and the corresponding signal analyses are carried out in the MATLAB programming environment.