Sector applications · Complies to IEC 62305-3 · IEC 61643-31

Rooftop Solar PV Protection

Rooftop PV protection keeps a solar array, its inverters and the building safe from direct strikes and surges. It combines air terminals that keep the array inside the protected volume, DC and AC surge protective devices, and bonding of the module frames and mounting structure.

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LPES solution codePVR

Governing standardIEC 62305-3 · IEC 61643-31

LPES design ruleFrame bonding 6 mm² or 16 mm²; DC SPDs at inverter and array

When it applies

Commercial and industrial rooftop PV plants
Buildings that already have a lightning protection system and are adding PV
Buildings without an LPS, where the array changes the lightning risk
String and central inverter systems up to 1,500 V DC

When it does not

Ground-mounted utility plants — see the ground-mounted PV, wind and BESS solution
Arrays whose DC voltage exceeds the continuous operating voltage of the selected SPD
Module-level electronics that the manufacturer protects internally — check before adding devices

How the system works

AssessA lightning risk assessment and the sector's own standard set the protection level.
Earth and bondEvery structure, frame and cabinet is joined to one earthing system.
Protect the linesCoordinated surge protective devices are fitted on power, DC, RF and data lines.
Monitor and maintainCounters and status contacts show what happened; inspection keeps the system in service.

Coordinated surge protection

Each device takes its share. The Class I device diverts lightning current at the service entry; Class II and III devices bring the remaining voltage below what the equipment can withstand.

Design parameters

The values a consultant or contractor needs to fix before the system is drawn.

Parameter	Typical value or rule	Reference
Risk and protection level	Risk assessment for the building with the array added	IEC 62305-2
Separation distance	Array kept at distance s from the LPS where possible; if not, frames are bonded to the LPS	IEC 62305-3 Cl. 6.3
DC SPD type	Type 2 when s is kept or there is no LPS; Type 1 or Type 1+2 when the array is bonded to the LPS	IEC 61643-32
DC SPD voltage	Ucpv at least 1.2 × the array open-circuit voltage at standard test conditions	IEC 61643-32 · IEC 61643-31
SPD location	At the inverter DC input; a second set at the array when the DC cable exceeds 10 m	IEC 61643-32
AC side	Type 2, or Type 1+2 with an LPS, at the inverter AC output and at the main board	IEC 61643-11 · IEC 60364-7-712
Bonding conductor	6 mm² copper minimum; 16 mm² copper where it may carry lightning current	IEC 60364-7-712 · IEC 62305-3

Solution pack: component BOQ

Each line opens the LPES product category. Part codes and final quantities are confirmed on your quote from the drawings.

Component	Role in the system	Quantity rule
DC & PV SPDs	DC surge protection at the inverter and array	One set per MPPT input, plus one at the array end where the cable is longer than 10 m
PV String Combiner Boxes	String combiner boxes with fuses, isolator and DC SPD	One per group of strings from the single-line diagram
Inverter AC Distribution Boxes	AC distribution box with breaker and AC SPD	One per inverter or inverter group
Earthing Kits	Electrodes and conductors for the array earth, bonded to the building earth	From the earthing design; typically two electrodes per array block
Air Terminal Rods	Keep the array inside the protected volume	From the rolling-sphere layout around the array

From design to handover

Assess the lightning risk for the building with the array
Lay out air terminals and check separation distance to the frames
Select DC and AC SPDs from system voltage, LPS status and cable lengths
Bond frames and structure and connect to the building earthing
Test earth resistance and SPD installation, and record in the plant file

Services for this solution

SPD Coordination Design Earth Resistance Testing

Industries that use it

Renewable Energy Commercial Buildings Manufacturing & Process

What the standards require

Checked against the current editions held in the LPES standards library.

IEC 62305-2:2024: Risk to life and physical damage is compared with a tolerable risk of 10⁻⁵ per year; failure of internal systems is judged separately as a frequency.
IEC 62305-4:2024: A coordinated SPD system protects against conducted surges only. Radiated fields need shielding and cable routing.
IEC 62305-4:2024 Cl. 7: Where an external LPS exists, a Class I (Type 1) SPD is required at the service entry.
IEC 62305-4:2024: Earthing conductor to the SPD: 16 mm² copper for Class I, 6 mm² for Class II and 1.5 mm² for Class III.
CEA Safety Regulations 2023, Reg. 38(3): Lightning protection is addressed for multi-storeyed buildings above 15 m and listed public premises such as airports, hospitals and hotels.
IEEE 80-2013: A substation grid is judged by touch and step voltage against the tolerable limits, not by its resistance alone.

Regulation and standards cross-check

What Indian regulation and the wider standards add to this solution. Paraphrased; confirm against the current official text, amendments and state notifications before relying on a clause in a tender or inspection.

Standard	Clause	What it requires
CEA Safety Regulations 2023	Reg 121	Solar plants need lightning and overvoltage protection with lightning arresters, a surge protective device with arc-extinguishing capability in every combiner box, earth-fault protection with insulation monitoring, and earthing of all array structures, frames and enclosures with welded strip connections.
IS 3043:2026	Clause 11.3	On solar plants the a.c. side is TN or TT and never TN-C. A separate protective conductor is always required, frame bonds are at least 6 mm² copper, and separate electrodes for the d.c. side, a.c. side, inverter or lightning protection are non-compliant.
CEA Safety Regulations 2023	Reg 38(3)(vi)	Lightning protection is required for multi-storeyed buildings above 15 m and for listed premises, which include hospitals, hotels, academic buildings, industrial installations and other public buildings. The regulation names no design standard, so IS/IEC 62305 applies through Reg 14.
IS 732:2019	Clause 1, 4.5.3, 5.3.5	The wiring code covers installations up to 1,000 V a.c. or 1,500 V d.c. Its surge clauses govern whether a surge protective device is needed and how it is selected, connected and coordinated.
IEC 60364-6:2016	6.4.3.3	Surge protective devices are disconnected for the insulation resistance test. Where that is impracticable the test voltage may be reduced to 250 V d.c., and the result must still be at least 1 MΩ.
CEA Safety Regulations 2023	Reg 43(v)	Every building shall have protective equipotential bonding that interconnects exposed and extraneous conductive parts.

What we ask for before design starts

Single-line diagram with sources, operating modes and earthing arrangement
Equipment list with impulse withstand levels
Cable routes and every point where services enter
Fault levels and protection clearing times
Existing earthing and lightning protection records
Site layout with fences, pipes, rails and neighbouring installations

Engineering depth: from the LPES Knowledge Hub

Topic studies written against the current standards. Open each part for the method, the mistakes to avoid and the checklist.

IEC 62305-4:2024 · LPES Knowledge Hub H-62

Roof-mounted PV systems current sharing with a non-isolated LPS and the simplified formula

When a rooftop PV array sits inside a structure's external lightning protection system (LPS) and the separation distance s to the down conductors cannot be maintained, part of the lightning current no longer stays on the LPS: it finds a second, ohmic path through the DC power cabling of the PV system, via the surge protective devices (SPDs) that bond the array frame and the DC conductors to the LPS. Annex F of IEC 62305-4:2024 gives a simplified way to estimate how much of the total lightning current — sized to the lightning protection level (LPL) — ends up flowing through each DC power conductor, so that the DC-side SPDs can be selected with a current rating that actually matches what they will be asked to carry. The governing simplified relationship is IDC = ILPL × kc / (2 × n′), where kc is the same down-conductor sharing coefficient used for the external LPS (IEC 62305-3:2024, 6.3.2, Table 13) and n′ is the number of DC power conductors and bonding conductors sharing the current at that point.

How it is applied

confirm the trigger condition: is the PV array's DC wiring, or its mounting frame, bonded to the structure's external LPS because the separation distance s cannot be maintained? If yes, this topic's method applies; if the separation distance is maintained, use the simpler In = 5 kA, 8/20, Class II rule from F.2.1 instead.
establish ILPL: read the LPL from the structure's IEC 62305-2 risk assessment, and take ILPL as 200 kA (LPL I or unknown), 150 kA (LPL II), or 100 kA (LPL III or IV).
establish kc: count the number of external down conductors on the LPS design (IEC 62305-3:2024) and read kc from Table 13 there (1 / 0,66 / 0,44 for one / two / three-or-more down conductors).
establish n′: count the DC power conductors plus bonding conductors that share the bonding point being assessed (a simple two-wire DC circuit with one separate bonding conductor gives n′ = 3, as in the worked example).
either calculate IDC directly with Equation (F.1), or read the equivalent pre-calculated per-pole and total values straight from Table F.1 (voltage-limiting/combination SPD) or Table F.2 (voltage-switching SPD), matching the LPL row and the "<4" or "≥4" down-conductor column.
select the DC-side SPD: it must be Test Class I (able to carry the 10/350 µs partial lightning current) whenever separation is not maintained, with a rated Iimp (or In, depending on SPD type) equal to or greater than the calculated/tabulated value.
where the design uses several string inverters (a larger plant), apply the Table F.1 values to the Class I SPDs on the AC side of the string inverters and at the low-voltage side of the central transformer; Class II SPDs are normally acceptable on the short DC run between a PV string and its own string inverter, provided that run has only one set of SPDs.
if separation is not maintained, also specify shielded DC cable or a metallic duct/conduit for the DC wiring, bond the shield at both ends to the local bonding bars, and design the shield itself to carry partial lightning current as if it were a down conductor.
where a less conservative, more precise figure is needed (e.g. because the simplified method's known over-estimation, per NOTE 2, is driving an uneconomical SPD choice), use the detailed calculation route of IEC 61643-32:2017, Clause A.2, instead of the Annex F simplification.

Common mistakes

Specifying an SPD by its AC surge rating alone and assuming it is automatically adequate for the DC side — F.1 states explicitly that SPDs between the array and the inverter must be rated for the DC rating of the array; DC-side surge duty is a separate design question from AC-side duty.
Treating the "separation distance maintained" case (Class II, In = 5 kA, 8/20, per F.2.1) and the "separation not maintained" case (Class I, Annex F.2.2 method) as interchangeable, or defaulting to the lighter Class II rating without first confirming which geometry actually exists on site.
Reading kc from memory or from a generic default instead of counting the actual number of down conductors on the specific structure's LPS design and pulling the correct value from IEC 62305-3:2024, Table 12.
Forgetting that Table F.1 and Table F.2 already assume a specific SPD topology (voltage-limiting/combination for F.1, voltage-switching for F.2) — mixing a Table F.1 current rating onto a switching-type SPD, or vice versa, does not carry the same safety margin.
Treating the shielding recommendation in F.1 (shielded cable or metallic conduit, bonded at both ends, when separation is not maintained) as optional good practice rather than as an integral part of the current-sharing protection concept — an unshielded, unbonded DC run in a non-isolated installation loses the induction-reduction benefit the annex assumes.
Using the Annex F simplified figures as if they were a precise prediction rather than the deliberately conservative overestimate NOTE 2 describes, then being surprised when a more detailed IEC 61643-32:2017 calculation gives a lower, more economical figure.
On multi-string plants, applying the short-DC-run Class II allowance (string to its own string inverter, single SPD set) to a DC run that is not actually short, or that carries more than one set of SPDs — the annex's relaxation for that case is conditional, not a blanket rule for all DC-side SPDs in a multi-inverter plant.

Design checklist

Confirmed whether the PV installation's separation distance s to the LPS is maintained or not, and documented which branch (F.2.1 Class II, or F.2.2 Annex F non-isolated method) applies.
Recorded the design LPL and the corresponding ILPL (200/150/100 kA).
Counted the external down conductors and recorded the applicable kc (1 / 0,66 / 0,44) from IEC 62305-3:2024, Table 12.
Counted n′ (DC power conductors + bonding conductors) at the bonding point being assessed.
Calculated IDC via Equation (F.1), or confirmed the applicable Table F.1/F.2 row and column, and recorded which of the two (voltage-limiting vs voltage-switching SPD) topology the selected SPD uses.
Verified the selected DC-side SPD is Test Class I, with Iimp (or In) at or above the calculated/tabulated value.
For a non-isolated installation, specified shielded DC cable or metallic conduit, bonded at both ends to the local bonding bars, and confirmed the shield is sized to carry partial lightning current.
For multi-string plants, confirmed which SPDs sit on the (Table F.1-rated) AC/transformer side versus the (potentially Class II) short DC string-to-inverter run, and that the "single SPD set, short run" condition for the Class II relaxation is actually met.
Where the simplified figures appear to force an uneconomical or oversized SPD, considered the detailed alternative calculation of IEC 61643-32:2017, Clause A.2.

Try the numbers

Protection level explorer

Rolling-sphere radius: 45 m
Mesh size: 15 × 15 m
Down-conductor spacing: 15 m
Peak current covered: 100 kA
Coefficient k_i: 0.04
Interception efficiency: 90%

Values from IEC 62305-1 and IEC 62305-3. The level for your structure comes from the risk assessment.

What we find on audits

Equipment earths and lightning earths kept separate
Surge protective devices chosen without coordination or the right voltage rating
Long connecting leads that add kilovolts to the protection level
Data and signal lines left unprotected while power lines are protected
No inspection after a strike, so failed devices stay in service

What you receive: the LPES Protection Passport

As-built drawings of the installed system
Risk assessment and design calculations
Test results: earth resistance, continuity, SPD checks
Component list with part codes and type-test references
Inspection schedule for the protection level

Lightning to Load: one accountable partner

Assess
Design
Specify
Supply
Implement
Verify
Assure

Standards basis

IEC 62305-2, -3 and -4:2024 (Ed. 3) · IEC 61643 series · IEEE 80-2013 · IEC 61936-1:2021 · IS 3043:2026 · CEA Safety Regulations 2023 · IS 732:2019 · IEC 60364-6:2016 · IEC 61936-1:2021

Reviewed by LPES engineering, November 2026. Clause and table numbers follow IEC 62305:2024 (Edition 3) and IS 3043:2026.

Questions engineers ask

Does rooftop solar need lightning protection?

The array does not attract lightning, but it adds exposed equipment. A risk assessment decides whether an LPS is needed; surge protection is recommended in all cases. Lightning Risk Assessment

Type 1 or Type 2 SPD on the DC side?

Type 2 when the array is kept at the separation distance from the LPS or there is no LPS. Type 1 or 1+2 when the frames are bonded to the LPS. DC & PV SPDs

Where should DC SPDs be installed?

At the inverter DC input, and also at the array when the DC cable between them is longer than 10 m. PV String Combiner Boxes

Should module frames be earthed?

Yes. Frames and mounting structure are bonded together and connected to the building earthing. Earthing Kits

Who coordinates the DC and AC protection?

An SPD coordination design sets the type, rating and location of every device from array to main board. SPD Coordination Design

Get this solution quoted for your site

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