Sample report — IEC 62305-2 lightning risk assessment

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.
Ground resistivity was not entered, so Table A.2's installation factor C_I is used as published for the buried line(s) — a value the table derives at ρ = 400 Ω·m. Above that, Table A.2 NOTE 3 gives a larger collection area (A_L = 0,6·√ρ·L_L: ×1,4 at 800 Ω·m, ×2,7 at 3 000 Ω·m), and N_L — with R_U, R_V, R_W and R_Z behind it — is understated in proportion. Enter the site resistivity if it may exceed 400 Ω·m.
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.
No zone was set for the Clause 9 assessment, so the frequency of damage F for loss of service was not evaluated and the verdict above is R against R_T only. §9.1 judges F separately from R: a structure providing a service — power, water, gas, telecommunications, transport — can satisfy R and still need protection under §9.3. Set the service criticality on any zone whose loss of service matters.

Methodology notes (Ed. 3.0:2024)

Risk is assembled per zone (§8.5.3) and judged against R_T by the §7.3 procedure. 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 F is assessed only for zones whose service criticality is declared, and none was declared here — see the assumptions above.

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, L = 30 m, W = 20 m, A_M = 194,376 m², k = 2 (§A.1 NOTE 1 fallback — where N_SG comes from a lightning location system, k is supplied by that provider)	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 load 'ordinary'
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 · P_TWS (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 · P_TWS · C_LD · r_t (eq. B.10)
P_V (power)	0.005	= P_EB · P_LD · P_TWS · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_TWS · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · P_TWS · 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 · P_TWS · C_LD · r_t (eq. B.10)
P_V (telecom)	0.005	= P_EB · P_LD · P_TWS · C_LD · r_f · r_p (eq. B.11)
P_W (telecom)	1	= P_SPD · P_TWS · P_LD · C_LD (eq. B.12)
P_Z (telecom)	1	= P_SPD · P_TWS · 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 load 'high'
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 · P_TWS (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 · P_TWS · C_LD · r_t (eq. B.10)
P_V (power)	0.05	= P_EB · P_LD · P_TWS · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_TWS · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · P_TWS · 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 load 'ordinary'
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 · P_TWS (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 · P_TWS · C_LD · r_t (eq. B.10)
P_V (power)	0.0001	= P_EB · P_LD · P_TWS · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_TWS · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · P_TWS · 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 · P_TWS · C_LD · r_t (eq. B.10)
P_V (telecom)	0.0001	= P_EB · P_LD · P_TWS · C_LD · r_f · r_p (eq. B.11)
P_W (telecom)	1	= P_SPD · P_TWS · P_LD · C_LD (eq. B.12)
P_Z (telecom)	1	= P_SPD · P_TWS · 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 load 'high'
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 · P_TWS (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 · P_TWS · C_LD · r_t (eq. B.10)
P_V (power)	0.001	= P_EB · P_LD · P_TWS · C_LD · r_f · r_p (eq. B.11)
P_W (power)	1	= P_SPD · P_TWS · P_LD · C_LD (eq. B.12)
P_Z (power)	1	= P_SPD · P_TWS · C_LI (eq. B.13)

What this assessment does not cover. Stated for every assessment, whether or not it applies to yours:

National deviations. This assessment follows the IEC base document. The foreword of IEC 62305-2:2024 records differing practices in four places: in Germany r_p = 1 in all cases, P_TWS = 1 for R_B, R_C, R_M, R_V, R_W and R_Z, and the highest L_F1 / L_F2 of Table C.2 should be used; in Greece P_TWS = 1 in all cases; in Italy R_L1 (eq. 7) and R_L2 (eq. 8) must each be compared with the tolerable risk separately, where this assessment judges their sum R = R_L1 + R_L2 (eq. 6) — both values are printed per zone, so the Italian comparison can be made by hand; in the Netherlands and South Africa Annex D and Annex E should not be applied to usual studies, which matches what is done here. Check the national annex that applies to the site.
Annex D — the graphical evaluation of P_SPD from the SPD's protection level and the system's withstand. P_SPD is taken from the Table B.3 lookup on the declared coordination level, and Annex D's method is not offered.
Annex E — the detailed investigation of additional losses L_E to surrounding structures and the environment. Annex E is for specific applications and E.1 says most structures need no environmental risk, but where one is needed it is not computed here.
Lines composed of several sections (different routing, shielding or installation along their length). Each line entered is taken as uniform end to end; a composite line has to be assessed section by section.
The lightning density used is a gridded climatology unless a value is entered directly. A national N_G map or a lightning location system to IEC 62858 is a better source wherever one is available, and N_SG drives every N term in the assessment.
The protection measures this assessment recommends are sized elsewhere: an LPS is designed to IEC 62305-3 and a coordinated SPD system to IEC 62305-4. This tool decides whether protection is needed and to which level, not what to install.
Economic risk. IEC 62305-2 Ed. 3.0 deleted the R4 economic-loss component and the cost-benefit annex of Ed. 2, so no cost comparison is part of this edition and none is produced here.

Structure	Retail block — 3 storeys (sample)	Basis of calculation	IEC 62305-2:2024 (Ed. 3.0)
Engine	lightning-0.18.0-iec2024	Schema	v2

Lightning Protection Risk Assessment