Switches are simple elements that in most cases work on a mechanical principle. In this final work he is introduced to the concept of the switch and its types. The appearance of an electric arc and the method for extinguishing it are described. A detailed description is given different principles of operation and explains the difference between switches and disassemblies. The main criteria for selecting switches are rated current, rated break power and rated voltage of the electricity network. When selecting a switch, it is necessary to calculate the values of the short-circuit current after and before the switch. Formulas for obtaining the specified values are displayed and several examples of different switch selection are shown. Continuous monitoring of the state of the switch as well as diagnostic techniques this benefit operators may be of great benefit to operators, irrelevantly they were a medium voltage or high voltage installation. Various methods and techniques are listed and explained, primarily for anticipating maintenance procedures, preventing active monitoring, improvement of test methods and very accurate prediction of the end of life of the switchgea. As technology progresses every day, more economical switches with better characteristics and smaller dimensions are expected.