Lightnings: Risks, Causes and Protection Strategies
High-energy lightning strikes pose a fundamental threat to modern infrastructure. Today, there is no alternative to the continuous availability of electronic devices, telecommunications equipment, and information technology (IT) systems. Operators and users must be able to keep their systems running without interruption and continue to use them even during lightning events.
The Phenomenon of Lightning Strikes: Historical research and modern Threats
Since Benjamin Franklin’s groundbreaking physical experiments in 1749, the study of lightning strikes has been firmly established in the natural sciences. What was once regarded as a purely meteorological phenomenon has evolved, in our highly digitized society that relies on microelectronics, into a constant, life-threatening danger to sensitive networks.
The physical origins of lightnings
Lightning is a massive atmospheric spark discharge. It occurs between two oppositely charged regions in the atmosphere—typically within a thundercloud (cloud-to-cloud lightning) or between a thundercloud and the ground (cloud-to-ground lightning).
The lightning channel does not form uniformly but grows in successive, jerky leaps (stepped leader), creating a highly ionized plasma channel in the air. Only when this leader reaches the ground via the so-called spark discharge does the channel close, resulting in the actual main flash (back discharge). At that moment, a transient pulse current ranging from several tens of thousands to 200,000 amperes flows through the ionized channel.
Figure 1: Charge separation in a thundercloud. Positively charged ice crystals accumulate in the upper part of the cumulonimbus cloud, while negatively charged water droplets dominate the cloud base.
Figure 2: Initiation of the leader flash. Negative charge carriers in the leader flash gradually make their way toward the ground, where they induce a massive redistribution of charge (influence).
Figure 3: Formation of the capture discharge. A positive discharge (capture discharge) from objects near the ground or from the ground itself meets the approaching leader.
Figure 4: The main flash (backward discharge). After contact is made, the charge carriers in the high-energy main flash travel at enormous speeds between the thundercloud and the ground.
Figure 5: Charge equalization. The lightning strike has eliminated the voltage difference. After the transfer, the local soil has a more negative charge balance than it did before the event.
Direct vs. indirect effects of lightning strikes
For an effective protection concept in accordance with current standards (such as DIN VDE 0100-443 and -534), a strict distinction must be made between direct and indirect effects:
Direct effects (lightning current)
In the case of a direct strike, the lightning channel strikes the building directly (galvanic coupling). A transient impulse current flows with an extremely steep rising edge in the microsecond range and peak values of up to 200 kA. The consequences are both thermal and mechanical: building materials are shattered by the sudden vaporization of moisture, and there is an acute fire hazard.
The Protection Approach: The primary protection against fire and mechanical damage is provided by the external lightning protection system (traditional lightning rods, arresters in accordance with DIN EN 62305). These systems capture lightning in a controlled manner and safely divert the surge current into the grounding system via lightning current devices.
Indirect effects (transient overvoltages)
Damage caused by indirect coupling of an inductive or capacitive nature is far more common. Even lightning strikes occurring up to two kilometers away can introduce dangerous transient overvoltages into the power supply and data networks via galvanic, inductive, or capacitive coupling. High lightning currents in the ground also lead to a transient potential rise, which causes extreme voltage differences between conductors and immediately destroys connected electronic systems without adequate protection.
The Protection Approach: This is where internal surge protection comes into play. Through the coordinated use of surge protective devices (SPD, Types 1, 2, and 3), transient energy is gradually reduced to a level that is harmless to the end devices (residual voltage).
Why modern Surge Protection is essential!
The need for comprehensive protection strategies against transient overvoltages stems from three key factors in the modern technological world:
Increased susceptibility to interference: Highly integrated electronic components and semiconductor devices are extremely sensitive to even the slightest voltage spikes.
Economic risk: Costly operational interruptions, data loss, and production downtime caused by damage to electronic components are economically unsustainable in automated processes.
Infrastructural vulnerability: Modern data transmission networks and smart grid systems span vast geographic areas, thereby presenting an enormous target for electromagnetic interference.
Payments under Contents and Building Insurance for Damage Caused by Lightning, in millions of euros
Source: GdV, 2024 Flash Summary
