PV Surge Protective Devices: Ucpv, Up, Modes and Backup-Protection RFQ Evidence

“Type 2, 1000 V, 40 kA” is not a complete photovoltaic surge-protective-device specification. Those three labels do not say whether the voltage is the maximum continuous PV operating voltage, which current waveform the 40 kA value belongs to, what voltage protection level applies in each mode, how the device behaves on an unearthed PV circuit, or whether separate backup protection is required. A quotation based on that phrase can therefore place unlike devices in the same price column.

A useful RFQ starts with the array and inverter boundaries, then asks for the exact SPD manufacturer, family, part number, connection diagram and current official datasheet. The buyer should compare Ucpv, Up by protection mode, Type 1 or Type 2 duty, Iimp, In, Imax, Iscpv or short-circuit withstand evidence, disconnection method, backup-protection rule, status indication and enclosure integration as separate fields. Passing one field does not compensate for an unresolved field elsewhere.

This guide is a procurement and evidence method, not a lightning-risk assessment or a site design. The project electrical designer, equipment manufacturers, applicable installation rules and any lightning-protection design remain controlling. It does not claim that SINAWATTS manufactures, certifies, tests or stocks any SPD discussed here. For array voltage inputs, first use the cold-weather PV Voc guide. For string overcurrent questions, use the PV string-fuse sizing guide.

Freeze the PV application before comparing devices

The SPD is selected for a defined circuit, location and protection concept. Issue an application sheet that identifies the module, series count, parallel-string count, minimum design temperature, calculated maximum open-circuit voltage, inverter or controller model, MPPT arrangement, earthing arrangement, cable route, external lightning-protection system, building entrance points and intended SPD location. Include the governing code or standard edition and the responsible designer’s required protection concept.

Do not ask a supplier to infer these inputs from “residential solar” or a nominal system voltage. A 1000 V inverter does not prove that every connected array remains below a proposed Ucpv at the lowest credible cell temperature. The same product label can also hide different circuit arrangements: one MPPT may receive a single string while another receives several paralleled strings through a combiner. The available PV short-circuit current and protective-device arrangement can therefore differ.

The official IEC 61643-31:2018 product standard covers SPDs intended for the DC side of photovoltaic installations up to 1500 V DC and defines performance, safety, ratings and test methods for devices that limit surge voltage or divert surge current. Its official IEC record includes the June 2022 corrigendum. IEC 61643-32:2017 addresses selection, installation and coordination principles for PV applications, including the DC side up to 1500 V. Those records were checked on 2026-09-21. They define a standards framework; they do not approve an unnamed device for a particular array. IEC 61643-31 official record; IEC 61643-32 official record.

Use the following input sheet before requesting a price:

On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.

Ucpv is not simply the module’s nameplate Voc

Ucpv is the maximum continuous operating voltage value declared for a PV SPD under its applicable product framework. Procurement should compare it with the engineered maximum voltage that can appear at the proposed location, using the controlling design method. Do not compare it only with module Voc at standard test conditions, array Vmp or a marketing name such as “48 V solar.”

Cold raises crystalline-silicon module open-circuit voltage. Series connection adds voltage. Manufacturing tolerance, the adopted temperature basis and the project’s calculation rule can affect the result. The exact module datasheet and project calculation must therefore travel with the RFQ. A bidder should state its proposed SPD Ucpv and explicitly confirm that the quoted part number is the one represented by the returned datasheet.

Avoid an invented universal headroom percentage. Standards, equipment instructions and design practices can impose specific methods or margins, and a higher Ucpv is not automatically a better purchase. Raising the SPD voltage rating can also raise its declared voltage protection level or change other performance. The correct comparison asks whether the selected voltage boundary is adequate and coordinated, not which bidder offers the largest printed number.

For example, the current ABB OVR PV Type 2 product page checked on 2026-09-21 lists named 1000 V DC and 1500 V DC variants, with different Up values. ABB states 4 kV Up for its 1000 V option and 5 kV for its 1500 V option on that page. This is model-family evidence that voltage and protective performance must be compared together. It is not evidence that every 1000 V or 1500 V SPD has those values. ABB OVR PV Type 2 official page.

The buyer’s voltage row should read something like: “Calculated maximum PV open-circuit voltage at SPD location: ___ V DC, calculation revision ___; required minimum Ucpv: ___ V DC under the project design basis; proposed Ucpv: ___ V DC; source page: ___.” This makes an engineering assumption visible and reviewable.

Compare Up in every required protection mode

Up, the voltage protection level, is a declared device value associated with specified test conditions. A PV circuit can require comparison between the positive and negative conductors and between each live conductor and protective earth. The proposal should return a circuit diagram and state Up for every relevant mode, rather than one unlabelled number.

The modes commonly encountered in PV documentation include DC+ to DC−, DC+ to PE and DC− to PE. The exact internal arrangement matters, especially in unearthed or floating arrays where either pole can move relative to earth during a fault. A product described only as “two pole” or “three module” does not reveal its protected paths. Ask for the manufacturer schematic, terminal labels and permitted earthing arrangement.

ABB’s current OVR PV Type 2 page explicitly lists DC+ to DC−, DC+ to ground and DC− to ground modes for the named family. Phoenix Contact’s current PV-SET 4ST/1000DC/F-SPD-SC set page lists Ucpv 1000 V DC and Up no greater than 3.5 kV for L+ to L− and for L+/L− to PE on that exact four-string set. Those are useful examples of mode-labelled evidence. They should not be copied into a generic specification as universal PV SPD values. Phoenix Contact PV-SET 4ST/1000DC/F-SPD-SC official page.

The inverter or controller’s documented impulse withstand and the installation arrangement are needed to judge coordination. Datasheet Up alone does not include the added voltage associated with connecting-conductor inductance during a fast surge. Long, looped or poorly routed leads can undermine a favorable device value. Require an installation drawing that shows SPD location, lead routing, conductor lengths, bonding path and terminal method, then have the responsible designer review the complete installed protection level.

Ask bidders to fill this mode table:

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If a mode is not applicable, the supplier should explain why using the approved system diagram. A blank cell, a repeated marketing value or a distributor summary is not an explanation.

Keep Type 1, Type 2 and waveform values separate

An SPD category is tied to a test duty and installation role. Type 1 duty is associated with lightning-current impulse capability and Iimp, commonly expressed for a 10/350 microsecond waveform. Type 2 duty uses nominal and maximum discharge-current concepts such as In and Imax, commonly associated with an 8/20 microsecond current waveform. A combined Type 1+2 device can carry both sets of declarations. The responsible lightning and electrical design determines the required category.

Do not rank offers by the largest kA value without its symbol and waveform. “40 kA” could be Imax on one proposal and a different declared parameter on another. It is not legitimate to compare an 8/20 Imax directly with a 10/350 Iimp as though both represented the same stress. Require the supplier to return symbol, value, waveform, pole or mode, standard and datasheet page in separate columns.

The Phoenix Contact four-string set cited above illustrates the distinction. Its current official page lists Imax 40 kA using an 8/20 waveform, In 15 kA and Iimp 5 kA for the named assembly. Those three values describe different declared duties; none should be shortened to “40 kA SPD” in the released BOM. Similarly, the current DEHNcube YPV SCI family page and catalog describe exact model-specific configurations. A buyer should use the exact DEHN part record rather than carry a family headline into a substitute approval. DEHNcube PV official family page; DEHN 2025/2026 product catalogue.

IEC TR 63227:2020, checked on the IEC site on 2026-09-21, gives broader guidance for lightning and surge protection of PV power supply systems with attention to safety, function and availability. It is a technical report, not a product certificate. Use it and the governing installation framework to organize the protection concept; use the product standard and exact manufacturer record to qualify the proposed device. IEC TR 63227 official record.

Separate surge-current ratings from PV short-circuit capability

Iimp, In and Imax describe surge duties. They do not state the continuous PV current, available array short-circuit current or the device’s ability to handle follow current and failure conditions. Procurement needs a separate Iscpv, short-circuit current rating or manufacturer-defined PV short-circuit capability field using the terminology in the exact datasheet.

The current Phoenix Contact 2905540 product page, for example, lists Iscpv 10.6 A DC per string and Isc STC 8.5 A DC per string for that four-string set. The current ABB OVR PV Type 2 page states that the named products are self-protected up to an Iscpv/SCCR value of 10 kA. The scale and definitions differ because the products and assemblies differ. These examples reinforce the need to retain the manufacturer’s term, circuit scope and page context rather than copy a bare number.

Calculate the prospective PV current at the proposed SPD connection under the project rules. Show the number of paralleled sources, module Isc basis, correction factors, backfeed sources if any and upstream protective devices. Then compare that result with the device manufacturer’s permitted circuit and disconnection arrangement. The DC fuse voltage and interrupt-capacity guide explains why a protective device’s voltage and interrupting evidence must remain attached to the current calculation.

Do not assume an SPD connected in parallel carries the array’s normal operating current in the same way as a series device. The relevant concern is how it is connected, protected and safely disconnected under abnormal conditions. Ask for the exact connection drawing, internal disconnector description, end-of-life behavior and manufacturer’s backup-protection instruction.

Treat backup protection as a model-specific rule

“No backup fuse required” and “maximum backup fuse ___ A” are manufacturer statements that apply to defined devices, circuits, conductor arrangements and prospective currents. They are not generic benefits that can be moved between products. A separate fuse or breaker added without the manufacturer’s permitted scheme can also change voltage, coordination, enclosure heat and failure behavior.

For the named Phoenix Contact 2905540 string-combiner set, the current official page says backup fuse for branch wiring is not required. DEHN’s official DEHNcombo YPV technical sheet DS218/E/0819, still available on the manufacturer site and checked on 2026-09-21, states that the listed DCB YPV 1200 and 1500 variants can be used up to 10 kA without a backup fuse. Those statements remain confined to the exact product records and their conditions. A different Phoenix or DEHN model, a different wiring arrangement, a different prospective current or a changed conductor can produce a different rule. DEHNcombo YPV technical sheet DS218/E/0819.

The RFQ should require one of three controlled responses:

1. No external backup device required within clearly stated conditions, with the manufacturer page and circuit limit attached.
2. External backup device required, with its exact type, current, DC voltage, interrupt rating, characteristic, location and coordination instruction.
3. Condition-dependent rule, with the decision boundary and both permitted configurations shown.

Do not accept “integrated protection” without a schematic and ratings. Ask whether the device has thermal disconnection, short-circuiting technology, arc control or another manufacturer-defined safety arrangement, then use only the language supported by the current document. A remote contact or visual flag reports status; it does not automatically prove safe isolation.

Coordinate placement, cable length and interfaces

Map every energy entry path: PV DC conductors, AC supply, protective earth, data, antenna and external sensor circuits. A DC SPD at the inverter does not protect an unaddressed communications conductor. Nor does a high-rated DC device replace AC-side protection. The system designer should define which interfaces require protection and where coordinated stages are installed.

Cable length can affect whether another protection stage is needed. ABB’s current OVR PV page says additional PV SPDs may be required when cable lengths between SPDs exceed 10 metres. Treat that as ABB’s published application statement for its context, not as a universal rule for every project. IEC 61643-32 and equipment-manufacturer instructions should guide the project-specific coordination.

At each location, show conductor entry, SPD lead length, routing, cross-section, protective-earth termination, bend path and separation from unprotected wiring. Keep incoming and protected conductors from being bundled in a way that re-couples a surge. Follow the exact manufacturer instruction for permitted conductor sizes, stripping, torque and mounting orientation. If installed inside a combiner or enclosure, verify spacing, temperature, pollution, condensation and enclosure rating as an assembly.

An IP rating for an enclosure does not describe a loose SPD installed with open cable entries. If outdoor exposure is involved, qualify the box, glands, plugs, drains and assembly. The IP67 versus IP68 guide explains how to record test scope without converting a component rating into an assembled-system claim. The cable-gland sealing-range guide covers cable diameter, thread and sealing evidence.

Use a bounded hypothetical comparison

Hypothetical procurement screen — not a real system design or product approval. Assume the responsible engineer provides the following approved inputs: maximum PV open-circuit voltage at the SPD location is 920 V DC; the array is floating; the relevant equipment withstand boundary is 4.5 kV under the engineer’s coordination method; the required locations and SPD category have already been established; and the calculated PV short-circuit condition at the connection point is 8 kA.

Bid A proposes an exact device with Ucpv 1000 V DC, mode-labelled Up of 3.5 kV for DC+ to DC− and for live conductors to PE, and manufacturer evidence permitting the stated 8 kA condition without a separate backup fuse. Bid B proposes “1000 V, 40 kA” but provides no mode diagram, no Up and no PV short-circuit or backup rule. Bid C proposes a 1500 V device with mode-labelled Up of 5 kV and suitable short-circuit evidence.

Bid A passes this limited paper screen if the engineer accepts its complete installation and coordination evidence. Bid B remains unresolved even if its unit price is lowest because the missing fields prevent comparison. Bid C clears the continuous-voltage screen but does not clear the assumed 4.5 kV protection-level boundary on the information stated. The example does not prove that 1000 V is appropriate for a real 920 V calculation, because the governing margin and other voltage ratings must still be checked. It also does not say that all 1500 V devices have 5 kV Up.

Now change one input: the available PV short-circuit condition becomes 12 kA. A product statement limited to 10 kA would no longer pass that row. Purchasing cannot solve the mismatch by assuming an upstream device acts quickly enough; the manufacturer’s permitted coordination and the project protection study must be updated.

Normalize the RFQ into a decision table

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Require suppliers to mark every deviation. A proposal that omits a value should say “not provided,” not silently reuse the buyer’s target. Keep commercial fields—unit price, package quantity, spare cartridge, MOQ and lead time—separate from technical acceptance, and obtain them directly from the bidder. This guide supplies no commercial claims.

Verify the first article and receiving evidence

The first-article review confirms that the delivered assembly matches the approved record; it is not a substitute for the manufacturer’s type testing. Photograph the complete label, part number, Ucpv, category, status indicator and terminal markings. Confirm cartridge and base compatibility, keying, protective-earth connection, conductor preparation, tightening record, enclosure penetrations and wiring against the approved drawing.

If a replaceable module is used, record its full spare part number and rejection criteria. A cartridge with the same color or outline is not necessarily interchangeable. Check whether insertion changes a mechanical flag and whether a remote contact changes state as described by the manufacturer’s safe inspection method. Do not inject surge energy in a receiving inspection unless an approved specialist procedure explicitly requires it.

Receiving control should preserve lot identity where available, label photographs, quantity, packaging condition and document revision. Define quarantine rules for cracked housings, loose modules, corrosion, unreadable labels or mismatched bases. Any substitution in manufacturer, family, Ucpv, Up, category, internal circuit, backup rule or enclosure arrangement should return to engineering review.

The maintained project file should contain the approved array calculation, lightning/surge concept, equipment withstand evidence, SPD datasheet, certificate or test evidence required by the project, connection drawing, backup-protection decision, installation record, commissioning status and inspection plan. This evidence makes a future replacement far safer than a purchase order that says only “PV SPD.”

Source boundaries checked on 2026-09-21

The IEC, ABB, Phoenix Contact and DEHN records linked in this article were checked on 2026-09-21. Numerical values are attached to named products and pages. Manufacturer pages can change, so preserve the approved revision or PDF with the project. IEC 61643-31, IEC 61643-32 and IEC TR 63227 were used for scope and terminology; this article does not reproduce their requirements or claim compliance.

If you are preparing a PV combiner, inverter-entry or enclosure quotation, assemble the array calculation, one-line diagram, SPD schedule, equipment model and required evidence. SINAWATTS can use that package to identify the requested component and documentation scope; final electrical and lightning-protection approval remains with the responsible project parties.

Send your PV SPD evidence package for an RFQ

Buyer FAQ

Is a 1000 V DC SPD suitable for every array below 1000 V?

No. Compare the exact device’s Ucpv and all other applicable ratings with the project’s approved maximum voltage calculation, which must account for module data, series count and cold conditions under the governing method. Also verify earthing topology, protection level, short-circuit behavior and equipment instructions. A nominal array description below 1000 V is not enough.

Is Imax the same as lightning-current capability?

No. Imax is normally associated with a Type 2 discharge-current declaration and its stated waveform. Lightning-current capability for Type 1 duty is represented by Iimp under a different waveform and test concept. Keep the symbol, waveform, mode and category attached to every kA value.

Can I choose the SPD with the lowest Up?

Not from Up alone. The product must first fit the array voltage, topology, required category, modes, short-circuit condition and installation environment. Then compare mode-specific Up and the installed lead contribution with the protected equipment’s coordination boundary. A low device value does not repair a mismatched voltage or circuit.

Does “integrated disconnector” mean no backup fuse is needed?

Not automatically. Obtain the exact manufacturer backup-protection instruction and its limits for the proposed model and connection. Some named devices state that no separate backup device is required within defined short-circuit conditions; other devices require a specified external fuse or breaker. Do not transfer the rule between families.

Should the SPD be installed at the array, combiner or inverter?

That decision depends on the lightning/surge assessment, cable routes, equipment locations, external protection system and coordination rules. A project can require more than one stage. Ask the designer for a location schedule and require each bidder to price that schedule rather than choosing a convenient single point.

What information should be sent for an RFQ?

Send the site and code basis, one-line diagram, module and series/parallel configuration, cold-weather maximum Voc calculation, earthing arrangement, inverter/controller model, lightning-protection context, cable routes, required SPD locations, enclosure conditions and documentation list. Ask the bidder to return an exact part number, official evidence, mode diagram, all relevant ratings, backup rule, installation drawing and deviations.