Lightning risk assessment

One structure is assessed using common structure event frequencies. Zones have separate losses and probabilities. Each independent incoming route has its own line-event frequencies and is linked only to the affected zones. Baseline and proposed scenarios share the same physical exposure.

• Rectangular AD = LW + 6H(L + W) + π(3H)². AM = 1000(L + W) + π500². Annex A equations A.2 and A.7.
• ND = NG × AD × CD × 10⁻⁶; NM = NG × AM × 10⁻⁶. For each homogeneous line route, AL = 40LL and AI = 4000LL. NL/NI include CI × CE × CT; NDJ includes ADJ × CDJ × CT. A.4–A.11.
• RA/RB/RC use ND; RM uses NM. RU/RV/RW use NL + NDJ. RZ uses NI. Equations 6–13. Zone totals are then summed.
• PA = PTA × PB; PV = PEB × PLD × CLD; PU = PTU × PV; PW = PSPD × PLD × CLD; PZ = PSPD × PLI × CLI. Annex B.
• For each independently recorded internal system, PCi = PSPD × internal CLD. PMi = PSPD × (KS1 × KS2 × KS3 × min(1,1/UW))², or 1 for equipment not meeting its specified withstand. PC and PM combine enabled systems as 1 − ∏(1 − Pi). Standalone systems have their own records. Use manual combined PC/PM for isolation or other cases requiring a different justified model.
• For each risk, enter final normalised D1, D2 and D3 losses. They map to LA=LU, LB=LV, and LC=LM=LW=LZ respectively. R2 excludes D1; R3 includes only D2. R1 D3 is included only when life-threatening system failure is explicitly confirmed. R4 D1 is for animals.
• Annex D: CL = baseline R4 × asset value; CRL = proposed R4 × asset value; CPM = capital cost × (interest + amortisation + maintenance). Positive annual saving = CL − CRL − CPM > 0. Zero is break-even.

Use your lawful copy of Annex B to select values and confirm every condition for the measures being credited. Common reference values: PB none/IV/III/II/I = 1/0.2/0.1/0.05/0.02; PEB and PSPD none/III–IV/II/I = 1/0.05/0.02/0.01. Equipotential bonding and coordinated SPDs are separate measures. For PC reductions, check the LPS/natural-LPS, bonding and earthing conditions in B.4.

PLD depends on line shielding and equipment withstand (B.8); PLI depends on power/telecom type and withstand (B.9). Do not leave the initial 2.5 kV power-line assumptions in place for telecom lines or other equipment. Internal CLD can differ from the external line CLD under B.4.

Use Annex C to normalise losses against the whole structure. The R1 helper calculates occupancy/time, surface and fire/hazard factors using C.1–C.4. R2 uses service-user ratios (C.7–C.8); R3 uses cultural-value ratios (C.9); R4 uses animal, building, content and system-value ratios (C.10–C.13). Enter explicit zero only when the loss mechanism is inapplicable and record the reason.

• Categorical factors are validated on import and before calculation. Invalid selections are never presented as a different valid option.
• Shared protection records supply bonding, SPD, wiring and shielding factors. Standard selections are constrained; exceptional factors require a source, clause, scope and reason.
• Route/system PSPD differences require specific evidence. Perfect zero measure factors are rejected. Applicable PC reductions require an LPS or documented natural LPS.
• Engineering-input changes clear review declarations. Old external-review references are retained as superseded, user-entered records.
• Reports show assigned measures, changed loss assumptions and illustrative exposure sensitivity. The downloadable review package is a draft snapshot, not a signed issue.

• Restored the full π(3H)² term in AD; the workbook incorrectly divided this term by four.
• Separated whole-structure exposure from zone losses. Zone dimensions no longer create separate building strike frequencies.
• Replaced the workbook’s line collection areas with AL=40LL and AI=4000LL; restored CT in NDJ.
• RM now uses NM, not ND. RZ is calculated explicitly. RU, RV, RW and RZ are allocated to affected zones and relevant risk categories.
• PA is PTA×PB. PEB and PSPD are distinct; system probabilities include shielding/withstand factors and multi-system combination.
• Removed hard-coded generic losses and zero-valued R2/R3 placeholders. All selected categories require explicit zone loss schedules.
• R4 uses its own economic losses and optional Annex D evaluation; it is not built from human-life losses or given an automatic threshold pass.
• Inactive reserve rows are removed. Missing inputs block calculation, and edits invalidate previous reports.

Verified references: IEC 62305-2:2010 Annex E.2 (Tables E.5–E.8) and E.3 (Tables E.18–E.21). Exact arithmetic is retained; comparisons allow the rounding of published figures. Release 1.2 includes 100 checks: 22 original checks, 53 component/system/input checks and 25 reliability acceptance checks. These are assertions across a limited set of fixtures, not 100 independently verified engineering projects. This is authored verification, not independent third-party certification. Automated UI checks simulate controls; browser layout, print pagination and multi-user login have not been verified in this environment. Hospital examples, every protection-table combination and field designs have not been fully validated.

Automatic mode does not geometrically resolve overlapping collection areas, common line routes, mixed line sections or complex structures. Combine same-route lines using the governing case and account for overlapping areas once, per clauses 6.4–6.5. Document expert-derived areas/event frequencies using manual mode where appropriate. A single effective PLD/PLI must conservatively represent any combined route.

External-zone mode is shock-only (RA). Explosion assessment, off-site/environmental consequences, detailed LPS/SPD design and certification are outside this release. Do not use zero losses to hide excluded consequences. The tool does not implement later IEC editions.

Hosted pages and downloads use the portal’s access policy. Downloaded HTML works without login and cannot be remotely revoked. Save inputs separately as JSON; optional local drafts and revisions stay on the current device. There is no shared project database. Assessment data is not sent to a server. All reports remain draft; review names and references are user-entered records, not authenticated signatures.