Performs an IEC 62305-2 lightning risk assessment and risk management measures evaluation for a structure: collection area and expected annual flash frequency, the structure's own risk components (touch/step voltage risk RA, physical damage risk RB), a pass/fail check against the standard's tolerable risk threshold, and \u2014 if risk is too high \u2014 the minimum LPS (Lightning Protection System) class needed to bring it into compliance, with the resulting rolling-sphere radius, mesh size and down-conductor spacing.
Standards followed
IEC 62305-1 (general principles)IEC 62305-2 (risk management)IEC 62305-3 (physical damage & LPS design)
What it can do
- Collection area and flash frequency from structure dimensions and ground flash density.
- Structure risk R1 = RA (touch/step voltage) + RB (physical damage), checked against the standard tolerable risk RT = 1×10⁻⁵.
- Searches for the minimum LPS class (I-IV) that brings a failing structure into compliance, with rolling-sphere/mesh/down-conductor design values.
- Advanced: connected-line risk (RU/RV from power & telecom line data) added into R1, and SPD/LEMP protection coordination.
Example problem
This calculator's default scenario is modelled on the IEC 62305-2 Annex E 'country house' example.
- Compute collection area Ad from the structure's L, W, H and Cd.
- Compute expected flash frequency Nd = Ng × Ad × Cd × 10⁻⁶.
- Compute RA (touch/step voltage risk) and RB (physical damage risk) from the entered loss factors.
- Sum R1 = RA + RB (plus RU/RV connected-line risk on the advanced) and compare to the tolerable risk RT = 1×10⁻⁵.
R1 ≈ 2.5056×10⁻⁵ with connected-line risk included, above the tolerable risk RT = 10⁻⁵, so protection measures are needed.
Want the full step-by-step version?
The core computes structure-only risk (RA+RB); connected-line risk (RU/RV) and SPD/LEMP protection coordination are advanced features.