Lightning Protection & Earthing, Explained

What is IEC 62305 and does it apply to my facility?

IEC 62305 is the international standard for protection against lightning. It is published in parts covering general principles, risk management, physical damage to structures, and protection of electrical and electronic systems. It applies to most structures where lightning could cause loss of life, service interruption, or significant damage, which covers the great majority of commercial, industrial, and critical infrastructure facilities.

In New Zealand and Australia, the equivalent regional standard is AS/NZS 1768:2021. Whether and how the standard applies to a specific facility is exactly what a risk assessment determines.

What changed in the 2024 edition of IEC 62305-2?

The third edition of IEC 62305-2, published in 2024, replaced the 2010 edition and introduced several significant changes to how lightning risk is assessed. These include a single combined risk concept covering loss of human life and loss due to fire, a new treatment of damage frequency affecting the availability of internal systems, and the introduction of ground strike-point density (N_SG) in place of flash density (N_G) for counting dangerous events. The edition also recognises thunderstorm warning systems compliant with IEC 62793 as a protection measure.

If your last risk assessment predates this edition, it may be built on a superseded method. We explain the changes in more detail in our news section.

Is lightning protection a legal requirement?

It depends on your jurisdiction, sector, and the outcome of a risk assessment. In many cases lightning protection is not mandated outright, but demonstrating that lightning risk has been formally assessed and managed is expected as part of due diligence, safety management systems, insurance requirements, and asset integrity programmes. For regulated industries and critical infrastructure operators, a documented assessment to IEC 62305-2 or AS/NZS 1768:2021 is often the practical baseline.

We are not lawyers, and we do not give legal advice. What we provide is the engineering assessment and documentation that supports your compliance position.

How do I know if my facility actually needs lightning protection?

The honest answer is that you find out through a risk assessment rather than a rule of thumb. A quantitative assessment weighs your structure's characteristics, location, connected services, internal systems, and the consequences of a strike against a tolerable risk threshold. If the calculated risk sits below that threshold, you may need little or nothing. If it sits above, the assessment tells you specifically where protection is justified.

That approach avoids two common and costly mistakes: protecting against risks you do not have, and leaving real exposure unaddressed.

What is a lightning risk assessment, and what does it involve?

A lightning risk assessment is a structured calculation of the risk a facility faces from lightning, carried out to IEC 62305-2 or AS/NZS 1768:2021. It accounts for the structure, its location and local lightning activity, the services connected to it, the systems inside it, and the consequences of damage spanning safety, continuity, and economic loss. The result is a defensible figure you can compare against a tolerable limit, along with guidance on which protection measures reduce the risk most effectively.

Aetheric carries out assessments using the Skytree Scientific LRAplus® platform, which applies real-time lightning location data rather than dated regional estimates.

Why does the source of lightning data matter?

Under the current edition of the standard, the count of dangerous events depends on ground strike-point density (N_SG) for the facility's location. A regional average or an old keraunic-level estimate can misrepresent the actual exposure at a specific site. Using measured lightning location data for the facility vicinity produces a more accurate and more defensible assessment, which matters when the result has to stand up to an auditor, an insurer, or a board.

What is the difference between lightning protection and earthing?

They are related but distinct. Lightning protection is the broader system that intercepts a strike, conducts it safely down a defined path, and manages the surges it produces. Earthing, sometimes called grounding, is the part that disperses that energy safely into the ground and provides a common reference for bonding and surge protection. Good earthing is essential to lightning protection, but earthing also serves wider electrical safety functions. A complete protection strategy addresses both, along with surge protection for connected systems.

What does earthing testing measure?

Earthing testing measures how effectively a system disperses current into the ground. The core measurements include earth resistance, typically by the fall-of-potential method, and soil resistivity, which influences how an earthing system should be designed. These methods are set out in IEEE 81. A single passing number is not the whole story, though: testing tells you the condition of the system at the time of measurement, which is why earthing performance is best understood alongside design intent and, where warranted, modelling.

What are surge protective devices, and do I need them?

Surge protective devices, or SPDs, limit transient overvoltages so that a lightning surge does not destroy connected equipment. A lightning strike does not have to hit a building directly to damage what is inside it; surges can arrive through power, data, and signal lines. For facilities with sensitive or continuity-critical electronics, coordinated surge protection across the relevant zones is usually a necessary part of the protection strategy, specified to IEC 61643 / AS/NZS 61643. A single device at the service entrance is rarely sufficient on its own.

Which standards does Aetheric work to?

Our work is anchored on the current international and regional standards for lightning protection and earthing, including IEC 62305 (all parts), AS/NZS 1768:2021, IEC 61643 / AS/NZS 61643 for surge protection, IEEE 81 for earthing measurement, IEC 62793 for thunderstorm warning systems, and sector-specific standards such as API RP 2003 for petroleum facilities and IEC 61400-24 for wind turbines. We work across multiple jurisdictions and align each engagement with the standards and local authority requirements that apply to it.

Do you only work in New Zealand?

No. Aetheric is New Zealand-based and serves clients across APAC, the Middle East, and West Africa. Each region has its own standards landscape and regulatory requirements, and we align each engagement accordingly. If your facilities span more than one jurisdiction, that multi-standard fluency is part of what we bring.

What types of facilities do you work with?

We focus on critical and high-value infrastructure where the consequences of a lightning event are serious: data centres, energy and renewable assets, critical infrastructure, and oil and gas facilities. These are environments where downtime, safety, or asset loss carry a high cost, and where expert lightning protection is worth doing properly.