Lightning current arresters with low protection level - chance and challenge

The risk of fire due to a flashover between electrical and metal installation in a building is still given without lightning protection equipotential bonding also when a lightning protection system (LPS) is installed in this building. Therefore the potential equalisation between the LPS and the electrical installation is a basic requirement in lightning protection of buildings. Lightning current arresters (LCAs) are important components to ensure the potential equalisation between the lightning protection systems (LPS) and the electrical installation. Their application is required in IEC62305-3 (Protection against lightning - Part 3) and their selection and coordination is described in IEC62305-4 (Protection against lightning - Part 4). The steadily increasing number of electronic devices and their growing sensitivity against overvoltages require surge protective devices (SPDs), with a high lightning current carrying capability as well as a low protection level. The low protection level may cause a huge number of possible operations of the LCAs with possible follow currents driven by the low-voltage mains. The number of incoming surges, their energy content as well as the number and the amplitude of power-frequency follow currents determine the life cycle of the SPD. Today the assessment of risk becomes more and more important for the design of electrical and electronic systems also in the field of lightning protection (IEC62305-2 (Protection against lightning - Part 2)). The assessment of risk demands the specification of an expected life time of the installed devices. Also manufactures of SPDs have to specify the expected life time of their devices since an increasing number of projects are placed under the aspect of risk assessment.