In the introductory part, we defined overvoltages. We consider overvoltages on devices to be unwanted and dangerous phenomena because they endanger the safety of personnel, damage or completely destroy devices and cause malfunctions of devices. We can effectively protect a device from overvoltages if we know the characteristics of overvoltages well. One of the basic characteristics of overvoltages is the place and method of occurrence of overvoltages, i.e. the source of overvoltages. Overvoltages on LV installations are caused by: direct lightning strikes, indirect lightning strikes, switching on and off in the power system, switching on and off in LV installations themselves, etc. Knowing the source of overvoltages, we design a system for protection against lightning and overvoltages. The task of overvoltage protection is to conduct all excess energy caused by overvoltages past the protected equipment to the grounding system in the shortest possible time. In addition to the electrical characteristics of the arrester, the response speed is also an important feature for selecting protection. Since fast protective elements cannot meet the energy requirements, multi-stage protection is resorted to, and combinations of fast and slower, but more energy-efficient protective elements are used. In the end, we determined the method of choosing the appropriate surge protection device for low-voltage systems, which is based on a probabilistic approach.