6.2.3 Changes in length of metal wires as a function of ambient temperature

The thermal linear expansion of metals is a fundamental physical phenomenon that must be taken into account in the design and installation of lightning protection systems. Particularly in the case of long cable runs and changing weather conditions, linear expansion can lead to mechanical stress and material fatigue if it is not taken into account in the design.
Knowledge of thermal expansion coefficients and the effects of climatic conditions is crucial for the professional implementation of structural measures in lightning protection construction. Incorrect measurements or a lack of compensation options for changes in length can lead to mechanical stress, cracks, malfunctions and ultimately to failure of the lightning protection system.
Thermal expansion depends directly on the climate and temperature conditions at the installation site. In Germany, average annual temperatures range from approximately –15°C (winter minimum) to +40°C (summer maximum). With increasing climate change, extreme values are being observed more frequently. For planning purposes in lightning protection construction, it is therefore common to assume temperature ranges between -20°C and +80°C, whereby particular attention should be paid to roofs or façades exposed to strong solar radiation. Periodic temperature changes, such as those that occur over the course of a day or year, lead to cyclical changes in the length of metallic conductors. This repetition can also influence the long-term behaviour and fatigue strength of the materials.