Direct or indirect lightning: why is the distinction essential?
Moreover, when talking about protection against lightning , a confusion arises very often:
👉 all lightning is “a direct impact” .
In reality, we can distinguish two very different phenomena :
- direct lightning , which physically strikes a structure,
- indirect lightning , whose effects propagate over a distance.
👉 This distinction is fundamental because the dangers, the damage and the protection solutions are not the same .
⚡ Direct lightning: definition, mechanism and dangers
What is direct lightning?
Direct lightning refers to a lightning strike on a structure :
- industrial or commercial building
- silo, water tower, pylon
- church, monument, sensitive site
- reservoir, antenna, wind turbine
The lightning current then flows:
- by the point of impact,
- within the structure,
- towards the downpipe network,
- up to the grounding point .
Intensity of the phenomenon
- Lightning current: 30 to 200 kA
- Rise time: a few microseconds
- Extremely high thermal and electrodynamic energy
Risks associated with direct lightning
- 🔥 Fire in the structure
- 💥 Spalling of concrete or masonry
- ⚡ Internal power surges
- ⚠️ Serious danger to people
👉 Without a capture device , the impact is random.
🌩️ Indirect lightning: the most frequent danger
Definition of indirect lightning
Indirect lightning refers to the electromagnetic effects of a lightning strike located nearby , without direct contact with the protected structure.
A lightning strike generates:
- an intense electromagnetic field ,
- inductive and capacitive couplings ,
- differences in soil potential .
distance of influence
📌 According to the IEC 62305 ,
the electromagnetic effects of lightning can be felt up to about 1 km around the point of impact.
Main dangers
- 💻 destruction of electronic equipment
- 🔌 Power surges on electrical and telecom networks
- 🧠 Intermittent faults that are difficult to diagnose
- ⚠️ Dangerous step and contact forces for people
👉 Statistically , indirect lightning is the leading cause of damage in modern installations.
🔍 Difference between direct and indirect lightning
🛡️ Lightning protection: a comprehensive approach is essential
Common mirod
Installing just a lightning rod protects the building.
❌ False.
A lightning rod:
- protects against direct lightning ,
- does not eliminate the electromagnetic effects of indirect lightning.
Standards-compliant approach
Note that effective protection against lightning relies on:
1️⃣ External protection
- lightning rod (capture),
- current descents,
- appropriately sized grounding connections.
2️⃣ Internal protection
- equipotentialities,
- limitation of potential differences,
- coordinated surge protection.
3️⃣ Lightning risk analysis
- site exhibition,
- environment,
- activity,
- economic and human consequences.
👉 This is exactly the logic imposed by IEC 62305 and NF C 17-102 .
🧠 Explanatory diagram: direct lightning vs. indirect lightning
It should be noted that the LPS France diagram above clearly illustrates:
- On the left: direct lightning , its impact and destructive effects.
- On the right: indirect lightning , its electromagnetic fields and its invisible damage.
- at the bottom: the need for external + internal protection .
🎯 Conclusion
- Direct lightning strikes are rare but spectacular.
- Indirect lightning is frequent, invisible, and often more costly.
- A serious protection system must address both phenomena simultaneously .
- International standards require a comprehensive approach , not just a product.
👉 Ignoring indirect lightning leaves the door open to breakdowns, operational losses, and human risks.