About the LPS & SPD Coverage
Lightning protection (LPS) and surge protective device (SPD) design shields a solar plant from direct strikes and the surges they induce. The LPS air-termination layout is set by the IEC 62305 rolling-sphere method for the chosen protection level, and SPDs are placed at each DC/AC boundary to clamp transient over-voltages.
Formula
Rolling-sphere radius R by protection level (LPL)
- LPL I
- R = 20 m (highest protection)
- LPL II
- R = 30 m
- LPL III
- R = 45 m
- LPL IV
- R = 60 m (lowest protection)
How to calculate it
- 1Run a risk assessment per IEC 62305-2 to select the protection level (LPL I–IV) for the site.
- 2Apply the rolling-sphere method: any point the sphere of the chosen radius can touch needs air-termination (masts/mesh) coverage.
- 3Bond and down-conduct to a low-impedance earthing system.
- 4Place SPDs at the boundaries: Type 1 at the service entrance (direct-strike energy), Type 2 at inverter DC inputs and AC outputs (induced surges).
Worked example
For an LPL III site (rolling-sphere radius 45 m), air-termination masts are positioned so the 45 m sphere never touches a module or the inverter; Type 2 SPDs guard the inverter DC and AC terminals, with a Type 1 SPD at the incoming service.
What you can calculate
- IEC 62305
- Rolling sphere
- Air terminals
- Type 1/2/3 SPD
Standards & references
Frequently asked questions
Do solar plants really need lightning protection?
Yes. Arrays sit in open, elevated, conductive locations that attract strikes, and even a nearby strike induces damaging surges on DC strings and inverters. An LPS plus coordinated SPDs is standard practice and is often required by the DISCOM connection agreement and insurer.
What is the difference between a Type 1 and Type 2 SPD?
Type 1 SPDs handle the high-energy partial lightning current from a direct strike and go at the service entrance/main incomer. Type 2 SPDs handle lower-energy induced/switching surges and protect equipment — placed at inverter DC and AC terminals. They are used together in a coordinated cascade.
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