Measures for overvoltage protection offer safety for buildings against lightning strikes. They also protect electric and electronic devices against excessive voltages. Additional components are often installed in circuits to provide overvoltage protection for devices. These are connected in parallel to the components and take over their protective function within fractions of a second.
Examples of components used for overvoltage protection are gas and air discharge tubes, varistors, TVS diodes and thyristors. The characteristics of the different components vary. One difference lies within the intensity of the voltage at which they are activated (low, mains, medium, and high voltage). Additionally, their maximum duration of activation differs. Some varistors, for example, must be replaced after a high voltage event, as they lose some of their protective characteristics and leakage current can occur.
Overvoltage protection is usually provided for components that are particularly important, vulnerable or expensive. Circuits that can have a direct impact on the life and limb of people are also protected in a complex way. This category includes, for example, elevators, cranes, and medical equipment.
A complete concept of overvoltage protection aims at splitting the high voltage into numerous, smaller overvoltages. A distinction is made between coarse protection, medium protection and fine protection. While the overvoltages in modern systems for coarse protection are still about 1300 volts, the energy in fine overvoltage protection is already much better distributed. In this case, the overvoltage is reduced to a level that is tolerable for the connected components or devices. The correct distribution of the voltage is of great importance for the effectiveness of the entire system.