In order to determine the strength analysis or the time course of the deformation-stress state of the installation circuit breaker, the master's thesis presents the production of a simplified geometric-numerical model of the installation circuit breaker mechanism. The geometric-numerical model of the mechanism of the circuit breaker is made on the basis of the finite element method from the geometric model of a single-pole circuit-breaker of type C with a nominal current of 25 A. The geometric-numerical model enables simulation of the real time course of the components of the mechanism. Using the model, the time course of the deformation-stress state of the mechanism and the friction between the individual parts can be estimated. Critical parts of the mechanism will be determined in order to ensure its function and durability and the possibility of optimizing the geometry and materials of the components of the mechanism. With the help of high-speed camera recordings of real time course of motion of individual parts of the mechanism of the circuit breaker, the validation of the geometric-numerical model of the mechanism of the circuit breaker mechanism was also validated. The results of the numerical simulation of the time course of the deformation-stress state of the circuit breaker mechanism show that the shut-off mechanism of the circuit breaker is designed in such a way as to enable fast enough operation without breaking any of the parts of the mechanism.