AS 1768:2021 risk assessment, from inputs to least protection
Lumex runs the AS 1768:2021 risk method on Voltrace™, the way the calculation tool sold with the standard runs it: four types of loss, each judged on its own, then the smallest set of measures that brings all four within their tolerable values.
AS 1768:2021 is the Australian lightning protection standard from Standards Australia. It replaced AS/NZS 1768:2007 and applies in Australia only. Its risk method is a trimmed down form of the 2010 IEC approach, with fewer inputs and assumptions set for Australian conditions.
The printed standard gives the shape of the method. The collection areas, event counts and fixed constants live in version 5.0 of the calculation tool Standards Australia sells with it, so that tool is what Lumex reproduces. Voltrace is checked against the standard's own worked examples in Appendix C and against cases the tool computed itself. You enter the same answers the tool asks for, and every figure you get back names the clause or tool cell it came from.
What you tell Lumex about the structure
Five groups of answers, the same panels the tool itself uses. Each dropdown is a choice the standard defines, written in plain words.
The structure
Its length, width and height, how readily it catches fire, how sensitive it is to sparking, and the kind of internal wiring. You also say whether it stores explosives.
The location
The ground flash density Ng, read from Figure C.1 or a better local source, the environmental factor Cd for what surrounds the site, and how dense the service lines are around it.
The service lines
The power supply, overhead or underground, its cable and whether a transformer sits at the structure, plus how many other conductive services arrive overhead and underground.
The protection in place
The lightning protection level, from none through LPL IV to LPL I, the fire protection fitted, and whether surge protection sits at the point of entry, on the equipment, or both.
What a strike would cost
How hard the building is to evacuate, where people and systems sit, what a fire or an overvoltage would take from the public, from heritage and from the owner, and whether animals could be hurt by step and touch voltages.
Answers held to the rules
Lumex refuses a value the standard does not offer and only asks for a line's cable when that line exists, so the assessment you save is one the method can actually compute.
Four types of loss, each against its own tolerable value
The four risks are never added into one number. Each is compared with its own tolerable value, and the structure needs protection if any one of them is over its line.
R1 · human life
Loss of human life
Judged against Ra1 of 10⁻⁵ per year, the strictest of the four, and the headline figure Lumex leads with on an AS 1768 assessment.
R2 · service to the public
Loss of service to the public
The chance that a strike takes away a service people rely on, judged against Ra2 of 10⁻³ per year.
R3 · cultural heritage
Loss of cultural heritage
Table 2.1 prints 10⁻⁴ per year here, while the standard's tool and its worked Figure C.2 apply 10⁻³. Lumex applies 10⁻³ so your figures match the tool, and the report states both values.
R4 · economic
Economic loss
The one tolerable value you pick yourself. Choose the loss the owner can accept about once a decade, once a century or once a millennium, which is 10⁻¹, 10⁻² or 10⁻³ per year.
Eight components, direct and indirect
Each component is a count of dangerous events times the chance of damage times the size of the loss. The first three make up the direct risk Rd, the other five the indirect risk Ri.
| Component | Where the strike lands, and what it does | Counts toward |
|---|---|---|
| Rh | On the structure, with step and touch voltages that can harm people or animals | R1, R4 |
| Rs | On the structure, starting a fire or other physical damage | R1 to R4 |
| Rw | On the structure, failing its electrical and electronic systems | R1, R2, R4 |
| Rg | On a connected service, carrying a dangerous voltage indoors | R1, R4 |
| Rc | On a connected service, bringing a fire in with it | R1 to R4 |
| Rm | Near the structure, inducing overvoltages in its systems | R1, R2, R4 |
| Re | On a connected service, failing the systems it feeds | R1, R2, R4 |
| Rl | Near a connected service, inducing overvoltages it carries inside | R1, R2, R4 |
Section 2 names the same eight in IEC letters, RA to RZ, and Appendix B uses the older letters above. Lumex follows Appendix B, as the tool does, and Lumi understands either set of letters. Every collection area and yearly event count behind these components, for the structure and for each overhead and underground line, is printed in the report.
The least protection that clears all four
Lumex works up from no protection and stops at the first package that brings every risk within its tolerable value. Fire protection stays as you entered it, because the standard's worked examples leave that choice to the engineer.
Protection level, then surge protection
It tries each lightning protection level from LPL IV up to LPL I, then adds surge protection at the point of entry, on the equipment alone, and finally both.
Lowest cost first, an alternative beside it
The standard does not say whether a lower protection level beats fewer surge devices. Lumex lists the lowest level first as the likely cheaper package and, where the two orders differ, shows the fewer surge devices option too. That ordering is a Lumex choice, not a rule of the standard.
Surge protection with every LPS
Where a service line comes in, Section 4 wants surge protection at the point of entry whenever an LPS is fitted, so the search never offers an LPS without it. If the protection you declared breaks this, the result warns you.
Explosives stores
A structure holding explosives needs LPL I with surge protection at the point of entry whatever its risks (J.5.1, J.5.2). Lumex searches only those packages, and marks a store that falls short as not compliant even when all four risks pass.
If LPL I with both surge measures still leaves a risk over its line, Lumex shows that strongest package with the risk it leaves, so you can see which components need other measures (B.4.2, B.4.3). Wherever an LPS is in play, the result also reminds you to bond metallic services such as gas and water pipes at the point of entry (3.6.2(c)), which the tool has no input for.
Australia also adopts the IEC series as AS/NZS IEC 62305, which Lumex runs as an IEC 62305-2 assessment, so both Australian routes are covered. New Zealand uses AS/NZS IEC 62305 only. Final responsibility for every result rests with the signing engineer, and Lumex does not replace professional judgement or the published standard.
An office building, four risks judged apart
An illustrative building, computed by Voltrace. The same inputs give the same four figures in version 5.0 of the Standards Australia tool.
20 m by 15 m, 10 m high, used as offices
- Ground flash density Ng of 0.1 per km² per year, among objects of similar height
- An overhead power line and one other overhead service, both unscreened
- Protection in place: LPL II with automated fire protection, no surge protection
- Medium occupancy, with the economic line set at one loss in a hundred years
All four within their tolerable values
- R1, human life: 2.9 × 10⁻⁶ per year, against 10⁻⁵
- R2, service to the public: 4.8 × 10⁻⁵ per year, against 10⁻³
- R3, cultural heritage: not relevant here, 0 against 10⁻³
- R4, economic: 3.5 × 10⁻⁸ per year, against 10⁻²
Each risk is the sum of its Appendix B components, compared with its own tolerable value, never added to the others. With LPL II already in place, no further protection is needed for this building. The values are illustrative; your figures depend on your own site and answers.
What goes into the document you sign
The full report opens with the verdict for each type of loss and a chart of all four risks, then lists every answer you gave with its reference, the collection areas and yearly events for the structure and its lines, the components behind each risk, and a calculation trace that shows how each figure was reached. It closes with the recommended protection and the risks that protection leaves, a conclusion, and a table of abbreviations. A short report carries the verdict, a summary of what was assessed and your site photographs.
You can also propose protection of your own, and Lumex works the assessment again with it in place, shown beside the protection as it stands. The proposal is a Lumex feature, not a step of AS 1768:2021, and it never changes the verdict, which always follows the protection actually in place. If the saved figures no longer match a fresh calculation, Lumex asks you to recompute before it will print the report, so the trace always explains the numbers beside it.
Every clause, table and figure the report cites is AS 1768:2021, and a reference to the tool names the tool cell instead. Lumex is an independent product and is not affiliated with or endorsed by Standards Australia. The authoritative method is set out in AS 1768:2021, available from Standards Australia.
Periodic inspection reports
Once the protection is installed, it has to be inspected over its life. Periodic inspection reports for AS 1768:2021 are in development and not yet available. Today every assessment carries a review date, with an email reminder a month before it falls due.
Lumi speeds the routine. Voltrace still owns every number
Lumi answers from your saved assessment through Voltrace itself. The signing engineer stays in control at every step.
Any figure, explained
Ask about a symbol such as Nd or Rs and get the working behind it, with the clause or tool cell it rests on.
A different size of building
Change the length, width or height and see how each of R1 to R4 moves, without touching the saved assessment.
The same recommendation as the report
Ask what protection is needed and get the C.3.4.2 search the report prints, so the two can never disagree.
A drafted narrative
A plain summary of the four risks and what they mean for the structure, shown beside your result and carried into the report summary.
AS 1768:2021 in Lumex, questions answered
Which edition of AS 1768 does Lumex run?
Does Lumex give the same answer as the Standards Australia tool?
Are the four risks added into one number?
Which tolerable value does Lumex use for cultural heritage?
How does Lumex choose the protection?
Can I use it for a site in New Zealand?
What goes into the AS 1768 report?
What does Lumi do on an AS 1768 assessment?
Working to a different standard?
Each standard runs by its own method, and a figure from one is never mixed with another. Compare all three.
Lumex computes the method of the standard you choose, IEC 62305-2:2024, AS 1768:2021 or NFPA 780-2026, and shows the working. It does not certify a structure. You may not issue or submit a Lumex output until a competent person, qualified where the structure is located, has reviewed the inputs and the result and signed it.
AS 1768:2021 Table 2.1 sets a tolerable value for each type of loss, and the owner chooses the one for economic loss. Every AS 1768 assessment in Lumex states the values that applied.
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