The subject of this paper are switchgears that are applied to medium voltage power plants. This paper is divided into six main chapters: „Introduction“, „The teory of electric arc“, „Interupting current“, „Circuit breakers“, „Switchers and contactors“ i „Disconnectors and earthing relays“ Each chapter is made to match a certain part of the default task. All these chapters explain the basic notions related to the topic and also define the advantages and disadvantages. The frist part is: „Introduction“ where the reader gets introduced to the mid-range voltage network and importance of some switching devices. The electric arc is mentioned as the greatest danger to the switchgear and all elements connected to the circuit. The second part is: "The theory of electric arc". The purpose of this unit is to answer the next part of the task: "Show the occurrences in the background of the electric arc". Various types of outbreaks in gas are displayed and an electric arc is illustrated as a whole. The molecular movements of the electrical arc are explained and described with formulas. The third part is: „Interupting current“. This unit is intended to respond to the next part of the task: "Theorize circuit breaking techniques". The main differences between the interruption of DC and AC are described. The alternating current, by its nature of motion, comes alone to zero (sinus), while the DC power must be forced, for which it is necessary to invest more energy. Techniques of current interruptions in different media are described and the advantages and disadvantages explained. The best medias are vacuum and SF6 gas. The fourth part is: „Circuit breakers“. This whole part is closely related to the past because the circuit breakers are the most important element when interupting the current. They are the only element in the power system that can interupt high current currents. There are a lot of media used for interupting the current with circuit breakers. Throughout the whole part most of them are described and characterized. The fifth part is: „Switches and contactors". Two essential elements are introduced. The switch is an element that can set up and cut down the working current to a certain value. Contactors are mechanical switching devices that have a stable contact position that returns when no more power is supplied. In most cases switches are combined with fuses to replace disconnector combined with the circuit breakers to a certain voltage. The advantages of these elements and their disadvantages and various performances are mentioned. The sixth part is: "Disconnectors and earthing relays", which are the simplest switchgear design. Disconnectors serve to visually disconnect the current circuit that is not energized by the one being energized. This part is about the various disassembler performances and their advantages and disadvantages. Earthwalls are used to rent elements and/or parts of the plant and the network. They can conduct short-circuit current for short time but they can not normally conduct the current in normal mode of work for longer time. Fast earthing relays are used in APU systems and its advantages and disadvantages are mentioned. Usually, most of the manufacturers are tapping the disconnector along with earthing relays.