Retail block — 3 storeys (sample) — Lightning Risk Report

Assumptions for missing inputs — the engine filled in the following defaults; verify each before relying on this assessment:

The entered lines (power, telecom) are taken as the complete set of connected services. Any further metallic service — a second power feed, a data line between buildings — adds S3/S4 risk and would need its own line entry.
No structure was modelled at the far end of any line (N_DJ = 0, §A.2.5) — each line is assumed to come directly from the network. Where a line arrives from an adjacent structure (e.g. a plant building housing the transformer), flashes to that structure add dangerous events on the line.

Methodology notes (Ed. 3:2024)

Risk is computed and judged per zone against R_T (§8.5.3). The 2010 edition's n_z/n_t population scaling no longer exists — a zone's risk is not diluted by its share of the structure's occupants.
Loss values follow Table C.2; the former h_z hazard factor is absorbed into its rows. Physical-damage losses (R_B2, R_V2, …) carry no time-of-presence weighting — property is at risk whether or not people are present. Results therefore differ from 2010-edition worked examples by design.
Scope: risk R per Clause 8. The Clause 9 frequency-of-damage procedure (F vs F_T, internal-system availability) is not part of this assessment.

Risk zones

Risk is assessed for each risk zone and compared with the tolerable risk in that zone; protection is required unless every zone complies.

Risk component breakdown — governing zone

Recommended protection measures

Zone	Risk R	R_L1 (injury)	R_L2 (damage)	Tolerable R_T	Verdict
Sales floor	3.7e-05	9.76e-06	2.72e-05	1e-05	Exceeds
Storeroom	7.39e-05	1.76e-06	7.21e-05	1e-05	Exceeds

Component	Value	Description
R_AT	8.78e-08	Touch and step voltages — flash to the structure (S1)
R_B1	1.1e-06	Fire or explosion — injury to persons (S1)
R_B2	4.81e-05	Fire or explosion — physical damage (S1)
R_U	2.19e-08	Touch voltage via a connected line — injury to persons (S3)
R_V1	5.48e-07	Fire or explosion via a connected line — injury to persons (S3)
R_V2	2.4e-05	Fire or explosion via a connected line — physical damage (S3)

With the recommended measures every risk zone satisfies R <= R_T (projected governing-zone risk 5.42e-06/yr).

Detailed calculation steps

The derivation chain shared by every risk zone, with the substituted values and the clause each step implements — check any step against the standard.

#	Step	Working	Result
1	Lightning ground strike-point density IEC 62305-2:2024, §A.1, eq. A.1	`N_SG = k × N_G` k = 2, N_G = 4 /km²/yr	N_SG = 8 /km²/yr
2	Collection area of the structure IEC 62305-2:2024, §A.2.1.2, eq. A.3	`A_D = L·W + 2·(3H)·(L+W) + π·(3H)²` L = 30 m, W = 20 m, H = 8 m	A_D = 4,809.56 m²
3	Flashes to the structure IEC 62305-2:2024, §A.2.4, eq. A.5; Table A.1	`N_D = N_SG · A_D · C_D · 10⁻⁶` N_SG = 8, A_D = 4,809.56 m², C_D = 1 (isolated)	N_D = 0.0384765 /yr
4	Flashes near the structure IEC 62305-2:2024, §A.3, eqs. A.7/A.8	`r_M = 350/U_W ; A_M = 2·r_M·(L+W) + π·r_M² ; N_M = (1/k)·N_SG·A_M·10⁻⁶` U_W(min) = 1.5 kV → r_M = 233.333 m, A_M = 194,376 m², k = 2	N_M = 0.777502 /yr
5	Flashes to line 'power' IEC 62305-2:2024, §A.4, eqs. A.9/A.10; Tables A.2–A.4	`A_L = 40 · L_L ; N_L = N_SG · A_L · C_I · C_E · C_T · 10⁻⁶` L_L = 200 m → A_L = 8,000 m²; C_I = 0.3, C_E = 0.5, C_T = 1	N_L = 0.0096 /yr
6	Flashes near line 'power' IEC 62305-2:2024, §A.5, eqs. A.11/A.12	`r_I = 2000/U_W^1.8 ; A_I = 2·r_I·L_L ; N_I = (1/k)·N_SG·A_I·C_I·C_E·C_T·10⁻⁶` U_W = 2.5 kV, L_L = 200 m → A_I = 153,744 m²; k = 2	N_I = 0.0922464 /yr
7	Flashes to line 'telecom' IEC 62305-2:2024, §A.4, eqs. A.9/A.10; Tables A.2–A.4	`A_L = 40 · L_L ; N_L = N_SG · A_L · C_I · C_E · C_T · 10⁻⁶` L_L = 500 m → A_L = 20,000 m²; C_I = 1, C_E = 0.5, C_T = 1	N_L = 0.08 /yr
8	Flashes near line 'telecom' IEC 62305-2:2024, §A.5, eqs. A.11/A.12	`r_I = 2000/U_W^1.8 ; A_I = 2·r_I·L_L ; N_I = (1/k)·N_SG·A_I·C_I·C_E·C_T·10⁻⁶` U_W = 1.5 kV, L_L = 500 m → A_I = 963,975 m²; k = 2	N_I = 1.92795 /yr
9	Per-zone risk and verdict IEC 62305-2:2024, eqs. 6–9, Table 3, §7.3	`R = R_L1 + R_L2 ; each R_X = N_X · P_X · L_X (with P_P/P_e per Table 3)` per-zone components and resolved factors in the tables below	protection required unless R ≤ R_T = 1e-05 /yr in every zone

Resolved factors — zone Sales floor

Factor	Value	Derivation
P_P	0.342466	= t_z / 8760 (eq. B.14)
P_e	1	= 1 — time of exposure unknown (§B.12 NOTE 1)
P_am	1	Table B.1 (touch/step-voltage measures)
r_t	0.001	Table B.2 (surface of soil or floor)
r_f	0.01	Table B.6 (fire/explosion risk)
r_p	0.5	Table B.5 (fire-reducing provisions)
P_S	0.5	Table B.4 (construction material)
P_LPS	1	Table B.3 (class of LPS)
P_AT	0.001	= P_LPS · P_am · r_t (eq. B.2)
P_B	0.0025	= P_S · P_LPS · r_f · r_p (eq. B.4)
L_T	0.01	Table C.2 typical value
L_F1	0.05	Table C.2 typical value
L_F2	0.05	Table C.2 typical value
K_S2	1	zone shielding screen (§B.6, eq. B.9)
P_C	1	= 1 − Π(1 − P_SPD·C_LD) over internal systems (eq. 10; eq. B.5)
P_M	1	= 1 − Π(1 − P_SPD·(K_S1·K_S2·K_S3)²) (eq. 11; eqs. B.6/B.7)
C_LD (power)	1	Table B.9 (line shielding/grounding/isolation)
C_LI (power)	1	Table B.9 (line shielding/grounding/isolation)
P_EB (power)	1	Table B.13 (line-entrance bonding SPDs)
P_LD (power)	1	Tables B.11/B.12 (line shielding vs U_W)
P_U (power)	0.001	= P_am · P_EB · P_LD · C_LD · r_t (eq. B.10)
P_V (power)	0.005	= P_EB · P_LD · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · C_LI (eq. B.13)
C_LD (telecom)	1	Table B.9 (line shielding/grounding/isolation)
C_LI (telecom)	1	Table B.9 (line shielding/grounding/isolation)
P_EB (telecom)	1	Table B.13 (line-entrance bonding SPDs)
P_LD (telecom)	1	Tables B.11/B.12 (line shielding vs U_W)
P_U (telecom)	0.001	= P_am · P_EB · P_LD · C_LD · r_t (eq. B.10)
P_V (telecom)	0.005	= P_EB · P_LD · C_LD · r_f · r_p (eq. B.11)
P_W (telecom)	1	= P_SPD · P_LD · C_LD (eq. B.12)
P_Z (telecom)	1	= P_SPD · C_LI (eq. B.13)

Resolved factors — zone Storeroom

Factor	Value	Derivation
P_P	0.0228311	= t_z / 8760 (eq. B.14)
P_e	1	= 1 — time of exposure unknown (§B.12 NOTE 1)
P_am	1	Table B.1 (touch/step-voltage measures)
r_t	0.01	Table B.2 (surface of soil or floor)
r_f	0.1	Table B.6 (fire/explosion risk)
r_p	0.5	Table B.5 (fire-reducing provisions)
P_S	0.5	Table B.4 (construction material)
P_LPS	1	Table B.3 (class of LPS)
P_AT	0.01	= P_LPS · P_am · r_t (eq. B.2)
P_B	0.025	= P_S · P_LPS · r_f · r_p (eq. B.4)
L_T	0.01	Table C.2 typical value
L_F1	0.05	Table C.2 typical value
L_F2	0.05	Table C.2 typical value
K_S2	1	zone shielding screen (§B.6, eq. B.9)
P_C	1	= 1 − Π(1 − P_SPD·C_LD) over internal systems (eq. 10; eq. B.5)
P_M	1	= 1 − Π(1 − P_SPD·(K_S1·K_S2·K_S3)²) (eq. 11; eqs. B.6/B.7)
C_LD (power)	1	Table B.9 (line shielding/grounding/isolation)
C_LI (power)	1	Table B.9 (line shielding/grounding/isolation)
P_EB (power)	1	Table B.13 (line-entrance bonding SPDs)
P_LD (power)	1	Tables B.11/B.12 (line shielding vs U_W)
P_U (power)	0.01	= P_am · P_EB · P_LD · C_LD · r_t (eq. B.10)
P_V (power)	0.05	= P_EB · P_LD · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · C_LI (eq. B.13)

Projected outcome with the recommended measures

The same assessment re-run with the recommended protection measures applied. The projected figures are reproducible from the post-measure factors below, exactly as the unprotected result is from the tables above.

Resolved factors with measures applied — zone Sales floor

Zone	Projected R	R_L1 (injury)	R_L2 (damage)	Tolerable R_T	Verdict
Sales floor	1.26e-06	3.31e-07	9.29e-07	1e-05	Pass
Storeroom	5.42e-06	1.26e-07	5.29e-06	1e-05	Pass

Factor	Value	Derivation
P_P	0.342466	= t_z / 8760 (eq. B.14)
P_e	1	= 1 — time of exposure unknown (§B.12 NOTE 1)
P_am	1	Table B.1 (touch/step-voltage measures)
r_t	0.001	Table B.2 (surface of soil or floor)
r_f	0.01	Table B.6 (fire/explosion risk)
r_p	0.5	Table B.5 (fire-reducing provisions)
P_S	1	= 1 with an LPS installed (Table B.4 NOTE 1)
P_LPS	0.05	Table B.3 (class of LPS)
P_AT	5e-05	= P_LPS · P_am · r_t (eq. B.2)
P_B	0.00025	= P_S · P_LPS · r_f · r_p (eq. B.4)
L_T	0.01	Table C.2 typical value
L_F1	0.05	Table C.2 typical value
L_F2	0.05	Table C.2 typical value
K_S2	1	zone shielding screen (§B.6, eq. B.9)
P_C	1	= 1 − Π(1 − P_SPD·C_LD) over internal systems (eq. 10; eq. B.5)
P_M	1	= 1 − Π(1 − P_SPD·(K_S1·K_S2·K_S3)²) (eq. 11; eqs. B.6/B.7)
C_LD (power)	1	Table B.9 (line shielding/grounding/isolation)
C_LI (power)	1	Table B.9 (line shielding/grounding/isolation)
P_EB (power)	0.02	Table B.13 (line-entrance bonding SPDs)
P_LD (power)	1	Tables B.11/B.12 (line shielding vs U_W)
P_U (power)	2e-05	= P_am · P_EB · P_LD · C_LD · r_t (eq. B.10)
P_V (power)	0.0001	= P_EB · P_LD · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · C_LI (eq. B.13)
C_LD (telecom)	1	Table B.9 (line shielding/grounding/isolation)
C_LI (telecom)	1	Table B.9 (line shielding/grounding/isolation)
P_EB (telecom)	0.02	Table B.13 (line-entrance bonding SPDs)
P_LD (telecom)	1	Tables B.11/B.12 (line shielding vs U_W)
P_U (telecom)	2e-05	= P_am · P_EB · P_LD · C_LD · r_t (eq. B.10)
P_V (telecom)	0.0001	= P_EB · P_LD · C_LD · r_f · r_p (eq. B.11)
P_W (telecom)	1	= P_SPD · P_LD · C_LD (eq. B.12)
P_Z (telecom)	1	= P_SPD · C_LI (eq. B.13)

Resolved factors with measures applied — zone Storeroom

Factor	Value	Derivation
P_P	0.0228311	= t_z / 8760 (eq. B.14)
P_e	1	= 1 — time of exposure unknown (§B.12 NOTE 1)
P_am	1	Table B.1 (touch/step-voltage measures)
r_t	0.01	Table B.2 (surface of soil or floor)
r_f	0.1	Table B.6 (fire/explosion risk)
r_p	0.5	Table B.5 (fire-reducing provisions)
P_S	1	= 1 with an LPS installed (Table B.4 NOTE 1)
P_LPS	0.05	Table B.3 (class of LPS)
P_AT	0.0005	= P_LPS · P_am · r_t (eq. B.2)
P_B	0.0025	= P_S · P_LPS · r_f · r_p (eq. B.4)
L_T	0.01	Table C.2 typical value
L_F1	0.05	Table C.2 typical value
L_F2	0.05	Table C.2 typical value
K_S2	1	zone shielding screen (§B.6, eq. B.9)
P_C	1	= 1 − Π(1 − P_SPD·C_LD) over internal systems (eq. 10; eq. B.5)
P_M	1	= 1 − Π(1 − P_SPD·(K_S1·K_S2·K_S3)²) (eq. 11; eqs. B.6/B.7)
C_LD (power)	1	Table B.9 (line shielding/grounding/isolation)
C_LI (power)	1	Table B.9 (line shielding/grounding/isolation)
P_EB (power)	0.02	Table B.13 (line-entrance bonding SPDs)
P_LD (power)	1	Tables B.11/B.12 (line shielding vs U_W)
P_U (power)	0.0002	= P_am · P_EB · P_LD · C_LD · r_t (eq. B.10)
P_V (power)	0.001	= P_EB · P_LD · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · C_LI (eq. B.13)

Structure	Retail block — 3 storeys (sample)	Basis of calculation	IEC 62305-2:2024
Engine	lightning-0.4.0-iec2024	Schema	v2