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Calculation No.: Calc-001
Revision: A
Description:
Created By: Engineer Name
Project: Project Name
Project No.: P001
Client: Client Name

Lightning Risk Assessment (IEC 62305-2)

Risk assessment for R1 (loss of human life) per IEC 62305-2.

1. Input Parameters

Structure and environmental parameters for lightning risk assessment:
Parameter Symbol Value Notes
Structure Length L 40 m
Structure Width W 20 m
Structure Height H 10 m
Flash Density N_g 2 fl/km²/yr Lightning flash density
Location Factor C_d 0.5 Location: flat
Structure Type PB P_B 100 m Type: non_metal_roof
Touch/Step PA P_A 1 Protection: none
Internal Systems PC P_C 1 Systems: low_voltage (1 line(s)), SPD: none
Loss Factor LA L_A 0.01 Occupancy: occupied
Loss Factor LB L_B 0.1 Fire risk: ordinary
Loss Factor LC L_C 0.01 Consequence: standard

2.1 Collection Area (Ad)

Equivalent collection area per IEC 62305-2 eq. A.2:

Formula: $$ \begin{aligned} A_d &= L \times W + 2 \times 3H \times (L + W) + \pi \times (3H)^2 \\ &= 40 \times 20 + 2 \times 30 \times (40 + 20) + \pi \times 30^2 \\ &= 7227 \; \text{m}^2 \end{aligned} $$

2.2 Expected Strikes (Nd)

Expected number of dangerous lightning events per year:

Formula: $$ \begin{aligned} N_d &= N_g \times A_d \times C_d \times 10^{-6} \\ &= 2 \times 7227 \times 0.5 \times 10^{-6} \\ &= 0.00723 \end{aligned} $$

3. Risk Factor Lookups

PA = 1.0 (touch/step protection: none) PB = 0.1 (structure type: non_metal_roof) PC = 1 (internal systems: low_voltage, 1 line(s), C_LD = 1.0; P_SPD = 1.0 for surge protection none, IEC 62305-2 Tables B.3/B.4) LA = 0.01 (occupancy: occupied) LB = 0.1 (fire risk: ordinary) LC = 0.01 (consequence: standard)

4.1 Risk Component RA (Touch/Step Voltage)

Risk of injury from touch and step voltages:

Formula: $$ \begin{aligned} R_A &= N_d \times P_A \times L_A \\ &= 0.00723 \times 1 \times 0.01 \\ &= 0.0000723 \end{aligned} $$

4.2 Risk Component RB (Physical Damage)

Risk of physical damage (fire, explosion, mechanical):

Formula: $$ \begin{aligned} R_B &= N_d \times P_B^{eff} \times L_B \\ &= 0.00723 \times 0.1 \times 0.1 \\ &= 0.0000723 \end{aligned} $$

4.3 Probability PC (Internal Systems)

Probability of failure of internal systems over the n connected lines (IEC 62305-2 B.4; unshielded lines C_LD = 1, no connected line C_LD = 0; P_SPD per Table B.3):

Formula: $$ \begin{aligned} P_C &= 1 - (1 - P_{SPD} \times C_{LD})^{n} \\ &= 1 - (1 - 1 \times 1)^{1} \\ &= 1 \end{aligned} $$

4.4 Risk Component RC (Internal Systems)

Risk from failure of internal systems:

Formula: $$ \begin{aligned} R_C &= N_d \times P_C \times L_C \\ &= 0.00723 \times 1 \times 0.01 \\ &= 0.0000723 \end{aligned} $$

5. Total Risk R1

Total risk for loss of human life:

Formula: $$ \begin{aligned} R_1 &= R_A + R_B + R_C \\ &= 0.0000723 + 0.0000723 + 0.0000723 \\ &= 0.000217 \end{aligned} $$

6. Risk Comparison

Compare calculated risk against tolerable risk (RT = 10⁻⁵): Result: FAIL - Protection required

Formula: $$ R_1 = 0.000217 \quad > \quad R_T = 0.00001 $$

7. Required Protection Level

Lightning Protection Level: LPL I Rolling Sphere Radius: 20 m Mesh Size: 5 x 5 m Minimum Lightning Current: 3 kA Efficiency: 0.98

8. Summary

Total Risk R1: 2.17e-04 Tolerable Risk RT: 1e-05 OVERALL: FAIL - Protection Required Required Protection: LPL I

Approval:

This calculation has been reviewed and approved by:
Created By
Engineer Name
Date: ..........................
Checked
By: .............................
Date: ..........................
Approved
By: .............................
Date: ..........................
Client Approved
By: .............................
Date: ..........................

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