In recent years, the most emphasis has been focused on the radiated thereat. Conducted disturbances should not be neglected also. Short-circuits and overvoltages have the most important effects in the field of conducted disturbances in the main electrical network. The paper describes the impact of electrical disturbances on power equipment and presents a protection device with a microcontroller. The device measures the main network voltage and the consumed current through the analog digital conversion channels and reduces the voltage in the case of overvoltage.