The Three Components
A complete lightning protection system (LPS) is not a single device. It is a system of three coordinated components, each with a distinct function. Remove or compromise any one of them and the system fails — sometimes catastrophically.
Component 1 — Air Termination System: The air terminals (rods, ESE lightning rods, or mesh conductors) define the preferred attachment point for the lightning strike. Their job is to ensure the lightning terminates at a controlled, known location rather than at a random point on the structure.
Component 2 — Down Conductor System: The down conductors carry the intercepted lightning current from the air termination to the earth. They must be sized to handle the full peak current (100–200 kA depending on protection level), routed to minimise inductance, and bonded to any metallic structural elements they pass near — to prevent side flashes.
Component 3 — Earth Termination System: The earthing electrodes dissipate the lightning current into the soil. A low earthing resistance — ≤10 Ω per IEC 62305-3 — is essential. High earthing resistance creates high ground potential rise during a strike event, which is itself a significant hazard to personnel and equipment inside the structure.
Critical point: Without a designated path to earth, lightning does not simply disappear. It will find a path — through structural steel, water pipes, electrical wiring, or through the building materials themselves. The resulting fire risk, side flash hazards and equipment damage are often worse than a direct strike would have been with no system installed at all.
Why the Earthing System Matters Most
Ask most people what a lightning protection system consists of and they will describe the rod on the roof. But the earthing system is arguably the most important — and most frequently under-specified — component of the entire installation.
When a 30 kA lightning current is injected into an earthing electrode with a resistance of 100 Ω, the ground potential at that electrode rises by 3,000,000 V above the remote earth reference. That 3 MV potential difference appears across any service cable entering the building — power, data, telecommunications — and is the primary cause of equipment destruction from nearby lightning events.
Achieving the IEC 62305-3 target of ≤10 Ω requires careful electrode design. ORBITAL's earthing product range covers all soil conditions: solid copper earth rods for standard soils, copper-bonded rods for cost-sensitive applications, and ORBetter® Earthing Enhancement Solution for high-resistivity rocky or sandy soils where standard rods cannot achieve the target resistance.
What Happens Without Proper Down Conductors
Down conductors carry not just current but thermal and mechanical energy. A 100 kA strike depositing its specific energy into a conductor that is undersized, sharply bent, or in close proximity to structural steel can cause explosive vaporisation of the conductor, ignition of adjacent materials, or damaging side flashes to metallic objects nearby.
IEC 62305-3 requires a minimum conductor cross-section of 50mm² for copper, 70mm² for aluminium. Conductors must be routed as vertically as possible — a horizontal run of more than 0.5m creates a significant inductive voltage drop that can cause a flashover to the nearest earthed metalwork.
The Complete System — External and Internal LPS
The external LPS (air termination + down conductors + earthing) stops direct strikes. But a nearby strike — even one that hits a tree or open ground 200m away — induces voltages in all conductive loops inside the structure. Those induced voltages destroy unprotected electronic equipment.
The internal LPS — comprising equipotential bonding and coordinated surge protection devices (SPDs) — is the defence against this threat. Our Type 2 range — OSPD 101 (single-phase) and OSPD 4011-3P (three-phase intelligent) — is aligned with the earthing system to limit dangerous potential differences; service-entry Type 1 coordination is specified per project via consultancy. See the SPD overview and our full system design guide.