This standard is the first part of the IS/IEC 62305 series, establishing the general principles for protecting structures, their contents, and occupants from lightning. It introduces the concepts of risk assessment to determine the need for protection, defines Lightning Protection Levels (LPL), and provides the framework for the subsequent parts of the series.
Establishes general principles for the protection of structures and services against lightning, covering risk assessment and protection methods.
Quick Reference Values
Tolerable risk for loss of human life (R T)1 x 10^-5 per year
Tolerable risk for loss of service to public (R T)1 x 10^-3 per year
Tolerable risk for loss of cultural heritage (R T)1 x 10^-4 per year
Lightning Protection Level I (max current)200 kA
Lightning Protection Level III/IV (max current)100 kA
Key Formulas
R ≤ R_T — The fundamental condition where Risk (R) must be less than or equal to the Tolerable Risk (R_T)
R = N × P × L — The general risk formula, where N is the number of dangerous events, P is the probability of damage, and L is the consequent loss.
Practical Notes
This part does not provide design rules; it helps you decide IF protection is needed and to WHAT level (LPL). The actual system design is detailed in Part 3 and Part 4.
A full risk assessment as per Annex A is the mandatory first step before designing a lightning protection system. This is a complex calculation often requiring specialized software.
Understanding the difference between an external LPS (lightning rods, conductors, earthing) and an internal LPS (Surge Protection Devices - SPDs) is a fundamental concept introduced here.