Resources
Lightning risk assessment guides
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Check the spelling, try a shorter word such as a symbol (RT, ND) or a clause, or look it up in the glossary. You can also ask us for a guide.
New to lightning risk? Start here
Five guides, in the order an engineer learns the method.
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Step 1
What a lightning risk assessment decides
Who needs one, where its numbers come from, and what the report must hold.
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Step 3
How a risk is calculated
One example building, from the inputs to the pass or fail verdict.
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Step 4
Protection levels and zones
What the verdict asks of the protection you design.
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Step 5
Designing the protection
Air terminals, down conductors, earthing and surge protection, in order.
IEC 62305
International. The risk method used across most of the world.
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What is IEC 62305?
The international lightning protection standard, its four parts, who needs it, and what the 2024 third edition changed. -
The IEC 62305-2 risk method
How the combined risk R (injury to people and physical damage) and the frequency of damage F, and the nine risk components, are computed and compared against the tolerable values. -
How an IEC 62305 risk is calculated
A plain-English worked walkthrough of one risk calculation, from the inputs to the pass or fail verdict, on an example building. -
Lightning protection levels (LPL I to IV)
What LPL I to IV mean, how the risk assessment decides the level, and how it maps to the LPS class. -
Lightning protection zones (LPZ)
How IEC 62305 zones step the threat down from outside to equipment, plus the separation distance and bonding. -
What changed in IEC 62305-2:2024
Every third-edition change explained one by one, from the density term to warning system credit, and why the edition you compute on is part of the verdict. -
ESE air terminals and IEC 62305
IEC 62305 specifies conventional air terminations, not ESE devices; the ESE method lives in NF C 17-102, a separate national standard.
NFPA 780
United States. Annex L, from the simplified risk assessment to R1 to R4.
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What is NFPA 780?
NFPA 780 is the US standard for installing lightning protection systems. What the 2026 edition covers, chapter by chapter, and when it applies to you. -
NFPA 780 Annex L, section by section
NFPA 780 Annex L is the informative lightning risk assessment of NFPA 780-2026: a quick N_D against N_C screen, then a detailed R1 to R4 method. -
Is lightning protection required by code?
Is lightning protection required by code in the US? Only when a code, the AHJ, an insurer or a contract asks for it. What NFPA 780, IBC and the NEC say. -
What changed in NFPA 780-2026
NFPA 780-2026 is the current edition. What changed from 2020, chapter by chapter: renumbered clauses, new surge rules, N_SG in Annex L, yearly inspection. -
NFPA 780 zone of protection
The NFPA 780 zone of protection comes from roof device placement, the 1:1 and 1:2 angle rules or a rolling sphere of up to 150 ft. Radii, limits, mistakes. -
NFPA 780 air terminal spacing
NFPA 780 air terminal spacing: 20 ft on ridges and roof edges, 25 ft for 24 in terminals, 50 ft across wide flat roofs, and a 10 in minimum height. -
NFPA 780 grounding and bonding
NFPA 780 grounding, 2026 edition: electrode types and depths, the ground ring, bonding to the NEC service ground, bonding distance and the 10 ohm myth. -
NFPA 780 surge protection
NFPA 780 surge protection, Section 4.19: SPDs at every power service rated 20 kA, protectors on data lines, VPR limits, and the link to NEC Article 242. -
NFPA 780 inspection checklist
NFPA 780 inspection explained: yearly checks under Section 1.7, complete testing every 3 to 5 years per Annex D, a cited checklist and the records to keep.
AS 1768
Australia. Four losses, and the least protection that clears them.
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What is AS 1768?
AS 1768 is the Australian standard for lightning protection. What AS 1768:2021 covers, section by section: risk, air terminals, earthing, surges, safety. -
AS/NZS 1768:2007 vs AS 1768:2021
AS/NZS 1768:2007 was superseded in Australia by AS 1768:2021 but is still current in New Zealand. What the 2021 edition changed, and which applies to you. -
AS 1768 air terminal placement
AS 1768 air terminal placement uses the Appendix D rolling sphere: a 20 to 60 m radius set by the LPL, a doubled radius on flat roofs, and spacing rules. -
AS 1768 earthing
AS 1768 earthing explained: what AS 1768:2021 asks of the earth termination network, the 10 ohm target, electrode choices, bonding and how to measure it. -
AS 1768 surge protection
AS 1768 surge protection explained: when AS 1768:2021 Section 4 requires SPDs, where primary and secondary SPDs go, the zone ratings and Appendix F rules.
Every standard
Guides that apply whichever standard your project follows.
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Lightning risk assessment
What the assessment decides, who it applies to, where its input numbers come from, and what a report needs to contain to survive review. -
What is a lightning protection system?
The complete LPS: its parts, how IEC 62305, NFPA 780 and AS 1768 each specify one, and whether lightning protection really works. -
Lightning protection glossary
Plain definitions of the symbols and terms in a lightning risk assessment, from R and N_D to LPL, LPZ and SPD, each cited to its clause. -
Air terminal placement methods
The rolling sphere, mesh and protection angle methods for placing air terminals, and how NFPA 780 and AS 1768 differ. -
Separation distance calculation
How to work out the IEC 62305-3 separation distance s from k_i, k_c, k_m and l, with a worked example and the NFPA 780 and AS 1768 equivalents. -
Earthing for lightning protection
How the earth termination dissipates a strike: IEC Type A and B electrodes, NFPA 780 grounding and AS 1768 earthing, and how each is tested. -
Lightning protection inspection
How often to inspect under IEC 62305-3, NFPA 780 and AS 1768, what each inspection checks and what to record. -
SPD Types 1, 2 and 3 explained
Surge protective devices under IEC 62305, NFPA 780 Section 4.19 and AS 1768: the types, where each goes and how they coordinate. -
Audit-ready risk reports
What an auditor, insurer or authority needs to see in a lightning risk report, under IEC 62305, NFPA 780 or AS 1768. -
NFPA 780 vs IEC 62305 vs AS 1768
The three lightning standards side by side: where each applies, how their risk methods differ, and which one governs your project. -
Lightning protection system design
The IEC 62305 design sequence step by step, with how NFPA 780 and AS 1768 order the same design decisions. -
Lightning risk assessment software
What to compare when you choose a tool: the edition, the working behind each figure, the report and the jurisdiction.
Guides by country
How each country adopts the standard, and the national rules that change the numbers.
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IEC 62305 around the world
How IEC 62305 is adopted as a national standard, often word for word, across most of the world, and where the US differs. -
BS EN 62305 in the UK
What the British Standard is, how it relates to the IEC original, what the national annexes add, and what the March 2025 corrigendum changed. -
Lightning protection standards in Australia
Lightning protection standards Australia uses: AS 1768:2021 leads, and it points to AS/NZS 3000, AS/NZS 5033 and others. See which one governs your job. -
Lightning protection in New Zealand
Lightning protection in New Zealand still follows AS/NZS 1768:2007, as AS 1768:2021 is Australian only. What NZ law requires, and when IEC 62305 applies. -
IEC 62305 in Germany
Germany's recorded departure: r_p = 1 for all cases, so fire provisions earn no reduction in P_B or P_V. -
IEC 62305 in Greece
Greece's recorded departure: P_TWS = 1 for all cases, so a thunderstorm warning system earns no reduction in six components. -
IEC 62305 in Italy
Italy compares R_L1 and R_L2 with the tolerable risk separately, rather than their sum, and that is more permissive. -
Annex D and Annex E in national practice
The Netherlands and South Africa do not apply Annex D or Annex E for usual studies. What each annex contributes. -
SS 555 in Singapore
Part 2 is identical to IEC 62305-2:2010 and Part 1 is modified. The four Annex ZA deviations, and the Class III floor the risk assessment cannot go below. -
CTE DB SUA 8 in Spain
Spain's building code decides the protection question with its own Ne and Na formulas. IEC 62305 is not cited anywhere in the Documento Basico. -
MS IEC 62305 in Malaysia
Enforced under the Electricity Supply Act with a criminal penalty, phased across existing buildings from 2021, and mandated on the 2006 first edition.
Guides by sector
Why the risk changes with what the building is for, under each standard.
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Lightning protection for data centers
Why continuity of service, not the building, drives the lightning risk in a data center, under IEC 62305, NFPA 780 and AS 1768. -
Risk assessment for hospitals
Why hospitals carry exceptional life-safety risk, and how IEC 62305, NFPA 780 and AS 1768 each treat a healthcare campus. -
Lightning protection for telecom
Why telecom towers are struck so often, and how IEC 62305, NFPA 780 and AS 1768 protect the electronics that keep a network on the air. -
Protection for heritage buildings
Why historic buildings need protection, how each standard weighs the loss of heritage, and how to fit it without harming the fabric. -
Oil, gas and storage tanks
Why a flammable atmosphere makes lightning a high-consequence threat, and how IEC 62305, NFPA 780 and AS 1768 protect tanks and process areas. -
Risk assessment for renewable energy
Why solar farms, wind sites and substations need a lightning risk assessment, and what IEC 62305, NFPA 780 and AS 1768 each ask for. -
Lightning risk assessment for solar farms
Which structures to assess on a solar farm under IEC 62305-2:2024, why the cables usually carry more risk than the structures, and what lowers it. -
NFPA 780 tanks and flammable vapors
NFPA 780 tanks under the 2026 edition: when a metal tank protects itself, floating roof shunts and bypass conductors, tank grounding and nonmetallic tanks. -
NFPA 780 solar arrays and wind
NFPA 780 solar rules in Chapter 12: strike termination devices on rooftop and ground-mounted arrays, PV surge devices, grounding and wind turbines. -
Lightning risk in Australian mines
Lightning protection for mines in Australia: AS 1768:2021 Appendix M advice, Appendix J rules for magazines, and what Queensland and WA regulators expect. -
Solar PV lightning protection in Australia
Lightning protection for solar PV in Australia: what AS 1768:2021 Appendix N says, where AS/NZS 5033 fits, where SPDs go, and how solar farms are assessed.
Free tools
Calculators built on the standard's own equations, each citing the clause behind its result.
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Rolling sphere method calculator
A free calculator for the protected radius of a single mast, with IEC 62305, NFPA 780 and AS 1768 sphere radii in feet or metres. -
NFPA 780 risk assessment calculator
A free Annex L screen: compare the yearly strikes to the structure, N_D, with the tolerable frequency N_C, with every step cited to NFPA 780-2026. -
IEC 62305 collection area and N_D calculator
A free calculator for the collection area A_D, a roof protrusion's A_D' and the yearly strike count N_D under IEC 62305-2:2024 Annex A. -
Lightning protection level selector
Enter the risk components from an IEC 62305-2:2024 assessment and see the weakest class of LPS that brings R within R_T, with its design values. -
Separation distance calculator
A free IEC 62305-3:2024 calculator for the separation distance s: pick the class of LPS, the material and the down conductors, enter l and check the gap.
How Lumex™ works
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Traceable, reproducible risk
Why every risk figure, under IEC 62305, NFPA 780 or AS 1768, must come from the standard's own method and trace back to its inputs. -
The engineer signs, a reviewer checks
Why the person who prepares a risk figure should not be its only checker, what a reviewer looks at, and what the sign off record holds. -
How Lumex™ verifies its risk enginesThe worked examples printed in each standard that the Lumex™ engines are tested against, the tolerance each check allows, and what is not yet covered. -
The edition is part of the answer
Why every risk figure names the standard and edition it was computed on, because two editions of one standard are different risk models. -
An activity record that is only added to
What Lumex™ records about each assessment, why entries are only ever added, and where the record stops. -
Independent of protection products
Why the assessment recommends the least protection the standard needs, named as measures, and why Lumex™ sells no protection hardware.
Want to see the method run end to end? Read how an assessment works, clause by clause.
The tolerable risk in IEC 62305-2 is not a fixed constant.
Clause 7.3 NOTE 1 gives RT = 1 × 10⁻⁵ per year as a
representative value of tolerable risk and adds that another value may be set once
the case has been investigated in detail. The standard's introduction then lets national or local regulations fix
RT, the tolerable frequency of damage FT
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