Solar PV Surge Protection Devices that keep inverters and strings alive through the monsoon
DC SPDs tested to IEC 61643-31 for 600 V, 1000 V and 1500 V DC photovoltaic strings: Type 2 (In 20 kA / Imax 40 kA) and Type 1+2 (Iimp 6.25–12.5 kA) in the Y-configuration that stays safe on a string fault. Pluggable modules, remote contact, plus matching AC SPDs for the inverter output. Manufactured and certified by LPES International.
Get a QuoteTalk to an EngineerWhat is a solar PV surge protection device?
Which PV SPD does each location need?
| Location | SPD type | Rating | Why |
|---|---|---|---|
| String combiner box / SCB | Type 2 DC (or Type 1+2 DC if the array has an LPS and the box is within 10 m of a down conductor) | Ucpv 1000 V or 1500 V, In 20 kA, Imax 40 kA | First line of defence; protects the DC cabling and the inverter input |
| Inverter DC input (if more than 10 m from the SCB) | Type 2 DC | Ucpv to match the string, In 20 kA | Induced surges re-enter along long DC runs |
| Inverter AC output | Type 2 AC (or Type 1+2 AC at the main LT panel) | Uc 275 / 320 V, In 20 kA, Imax 40 kA | Protects the inverter from surges on the grid side |
| Plant main LT / evacuation panel | Type 1+2 AC | Iimp 12.5 kA, In 20 kA | Lightning current from the plant LPS or overhead line |
| Monitoring, RS485, Ethernet, weather station | Signal / data SPD | Per line voltage (5, 12, 24 V) | The surge path that most often kills the plant monitoring system |
Per IEC 61643-32 (selection and application of PV SPDs) and IS/IEC 62305-4.
Solar PV SPD range from LPES
1000 V DC PV SPD
Type 2, Ucpv 1000 V DC, In 20 kA, Imax 40 kA, Y-configuration, 3-module pluggable with remote contact. For rooftop and small ground-mount plants.
View 1000 V models →1500 V DC PV SPD
Type 2 and Type 1+2, Ucpv 1500 V DC, In 20 kA / Iimp 12.5 kA. For utility-scale 1500 V string inverters and central inverters.
View 1500 V models →All Solar PV SPDs
Every DC rating, class and pole configuration in the catalogue.
Browse the full range →PV Combiner Box
IP65 string combiner boxes with PV SPD, DC fuses and DC isolator pre-wired and tested.
See PV Combiner Boxes →How to select a solar PV SPD
1. Set Ucpv from the string open-circuit voltage
Take the module Voc at STC, multiply by the number of modules in series, and correct for the lowest site temperature (Voc rises about 0.3 % per °C below 25 °C). The SPD's Ucpv must exceed that figure: use Ucpv 1000 V for 1000 V-class strings and Ucpv 1500 V for 1500 V-class plants. Never use an AC SPD, and never install two 600 V SPDs in series to make 1200 V.
2. Decide Type 2 or Type 1+2 by the lightning protection arrangement
| Array arrangement | DC SPD class |
|---|---|
| No external LPS, or LPS with separation distance maintained from the array | Type 2 DC in the SCB and at the inverter |
| LPS bonded to the module frames / mounting structure, or separation distance not achieved | Type 1+2 DC (Iimp ≥ 6.25 kA per pole, 12.5 kA total) in the SCB |
| Plant on an open site with a strike density above 5 per km² per year | Type 1+2 DC in the SCB, Type 2 DC at the inverter |
3. Use the Y-configuration
A PV string cannot be switched off — it produces voltage whenever there is light — so a shorted varistor between + and − would draw a DC arc. The Y-configuration (three MOVs, +, − and the star point to earth, each with its own thermal disconnector) means any single failure leaves the string safe. All LPES PV SPDs use it; check for it in any competing datasheet.
4. Keep the 10 m rule
If the inverter DC input is more than 10 m of cable from the combiner box SPD, add a second Type 2 DC SPD at the inverter. The same applies on the AC side between the inverter and the LT panel.
5. Earth the SPD properly
The SPD earth terminal is bonded to the mounting-structure earth and the plant earth grid with 16 mm² copper (or 25 mm² GI strip) by the shortest route. Target under 5 Ω for the array earth, tied into the main earth grid. See the LPES earthing range and the earthing resistance estimator.
6. Do not forget the monitoring lines
Most inverter failures after a storm are traced to the RS485 or Ethernet monitoring line, not the DC input. Fit a signal SPD on every RS485 bus and PoE / Ethernet link that leaves the inverter room.
Limitations and trade-offs
A PV SPD does not make an array immune to a direct strike on the modules — that is the job of the lightning protection system (air terminals on the structure or isolated masts) and the earth grid. DC SPDs age with every surge and with sustained operation near Ucpv; a plant on an exposed site should have its SPD status contacts monitored and modules replaced when the indicator turns red, not on a calendar. Finally, 1500 V SPDs are physically larger and need the specified backup fuse and clearance inside the combiner box — retrofitting them into a 1000 V box designed without that space is a common cause of failure.
Datasheets, certificates and CAD
Every LPES product ships with a datasheet, test report reference and declaration of conformity. Download the current catalogue and product datasheets from the Downloads library, or ask for the CAD block and single-line drawing for your panel from the RFQ form below.
Frequently asked questions
Can I use a normal AC Type 2 SPD on a solar DC string?
No. AC SPDs are tested to IEC 61643-11 for 50 Hz systems and cannot interrupt a DC arc if a varistor fails. Solar strings need DC SPDs tested to IEC 61643-31 with a Y-configuration and DC-rated thermal disconnectors.
What is Ucpv and how do I choose it?
Ucpv is the maximum continuous DC voltage the SPD can withstand. Calculate the string open-circuit voltage at the lowest site temperature and choose an SPD with Ucpv above it: 600 V, 1000 V or 1500 V DC.
Where are PV SPDs installed in a solar plant?
In the string combiner box (SCB), at the inverter DC input if it is more than 10 m from the SCB, on the inverter AC output, in the plant main LT panel, and on the RS485 / Ethernet monitoring lines.
Do I need Type 1+2 DC SPDs or is Type 2 enough?
Type 2 DC is sufficient when there is no external LPS or the LPS keeps its separation distance from the array. Where the LPS is bonded to the module structure, or the separation distance cannot be achieved, use Type 1+2 DC with Iimp of at least 6.25 kA per pole.
Why is the Y-configuration important?
A PV string cannot be de-energised while there is light. In the Y-configuration each of the three varistors has its own disconnector and the star point goes to earth, so a single failed MOV cannot create a sustained DC arc between + and −.
What is the 10 m rule for PV SPDs?
If the protected equipment is more than 10 m of cable from the SPD, induced surges can re-enter along the cable and a second SPD is needed at the equipment. It applies between the combiner box and the inverter, and between the inverter and the AC panel.
Are LPES PV SPDs suitable for 1500 V central inverters?
Yes. The 1500 V DC range covers Type 2 (In 20 kA, Imax 40 kA) and Type 1+2 (Iimp 12.5 kA) in Y-configuration, with remote-signal contacts and the backup fuse specified in the datasheet.
Which standards apply to solar PV surge protection in India?
IEC 61643-31 for the SPD itself, IEC 61643-32 for selection and application, IS/IEC 62305-3 and -4 for the plant lightning protection, IS 3043 for earthing, and the MNRE / CEA technical standards for grid-connected PV which require surge protection at the inverter and evacuation panel.
Related pages
Protecting a rooftop or utility-scale solar plant?
Send the plant capacity, string voltage, number of combiner boxes and inverter model; LPES returns a DC + AC + signal SPD schedule with a BOQ in one working day.
