Lightning Protection System (LPS) Design for Pakistani Buildings 2026 — IEC 62305 Guide
How do I design a lightning protection system for a Pakistani building?
A complete LPS has three parts per IEC 62305: (1) an external system — air terminals (rods/mesh) on the roof, down-conductors to ground, and a dedicated earth termination network; (2) equipotential bonding tying all metalwork + the LPS earth together to stop side-flashing; and (3) an internal/SPD system — coordinated Type 1 + Type 2 surge protectors at the main and sub-DBs to stop the surge energy that the external LPS lets through. Pakistani monsoon zones (Lahore, Islamabad, Faisalabad, Multan) see 5-15 ground-flashes/km²/yr, so an LPS plus SPDs is essential for factories, rooftop solar, telecom towers and high-rise. Start with an IEC 62305-2 risk assessment to pick the protection level (LPL I-IV).
The 3 layers of protection
| Layer | Components | Job |
|---|---|---|
| External LPS | Air terminals, down-conductors, earth termination | Intercept the strike + carry it safely to ground |
| Bonding | Equipotential bonding bars, bonding conductors | Stop dangerous side-flashing between metal parts |
| Internal / SPD | Type 1 + Type 2 SPDs, coordinated | Clamp the surge that gets through, protect electronics |
Protection levels (LPL) from IEC 62305-2 risk assessment
- LPL I — highest protection (hospitals, fuel depots, explosives, data centres)
- LPL II — factories, large commercial, telecom
- LPL III — typical commercial/residential high-rise
- LPL IV — low-risk structures
- The LPL sets the air-terminal mesh size, rolling-sphere radius and down-conductor spacing.
SPD coordination (the part most Pakistani installs skip)
- Type 1 SPD at the main incomer — handles direct/partial lightning current (10/350 µs waveform).
- Type 2 SPD at sub-DBs — handles induced surges (8/20 µs).
- Type 3 at sensitive equipment if the cable run is long.
- SPDs must be coordinated (energy-matched) and earthed to the same equipotential network as the LPS — an SPD on a separate earth is useless.
Common Pakistani LPS mistakes
- Air terminal but no SPDs — the strike is grounded but the induced surge still fries every PCB in the building.
- LPS earth separate from electrical earth — creates a huge potential difference and side-flashing. Bond them.
- Single down-conductor — needs multiple, spaced per LPL, for a large roof.
- Rooftop solar with no LPS — the array is the highest metal object; mandatory air-terminal + DC SPD coordination.
- No re-test of earth resistance — LPS earth must stay low (<10Ω, ideally <5Ω); re-test annually.
Related
SPD Installation Guide · Earthing Systems · Surge/Lightning Arrester Guide