Most PV commissioning disputes are not about whether a test was done. They are about which tests were in scope, what counted as a pass, and whether the records survive a lender’s review. IEC 62446-1 answers all three questions, but only if the EPC and the owner agree on the test category before the first string is energised.
Quick answer. IEC 62446-1 acceptance testing verifies a grid-connected PV system before handover. Category 1 applies to every system and covers earthing, polarity, string voltage and current, functional checks, and insulation resistance. Category 2 adds an I-V curve test on every string, with results typically within 10% of the expected or adjacent value.
TL;DR
- The edition in force is IEC 62446-1 Edition 1.1 (2016 plus Amendment 1, August 2018).
- Category 1 is the minimum for every system. Category 2 adds string I-V curves and suits larger or financed plants.
- String current and I-V results should typically sit within 10% of the expected or adjacent string value.
- I-V performance checks need stable plane-of-array irradiance of at least 400 W/m2.
- A revision reached the committee draft for vote stage in 2025. Write the edition into the contract.
This guide is for EPC project managers, owner’s engineers, and O&M leads who sign off a plant. It covers the test regimes, the pass bands the amendment sets, and the handover file. It complements our guide to IEC 62548 array design, which sets the design rules these tests verify. For the wider site sequence, use our solar plant commissioning checklist.
What does IEC 62446-1 cover?
IEC 62446-1 sets the documentation, commissioning tests, and inspection criteria for grid-connected PV systems. Its subtitle is “Grid connected systems: Documentation, commissioning tests and inspection.”
The IEC webstore lists Amendment 1 as published on 10 August 2018 by Technical Committee 82. The consolidated text is Edition 1.1. The scope says the standard is a template for designers and installers to hand over effective documentation to a customer.
The series has three parts that people often confuse:
| Part | Subject | Current edition |
|---|---|---|
| IEC 62446-1 | Documentation, commissioning tests, inspection | 2016 + AMD1:2018 (Ed. 1.1) |
| IEC 62446-2 | Maintenance of grid-connected PV systems | Ed. 1.0, March 2020 |
| IEC TS 62446-3 | Outdoor infrared thermography of modules and plants | Ed. 1.0, June 2017 |
Sources: IEC 62446-2:2020 and IEC TS 62446-3:2017 on the IEC webstore, accessed 6 October 2026.
Is a new edition coming?
A revision is in progress. A German draft, E DIN EN IEC 62446-1:2026-01, is out for comment and is based on IEC committee draft 82/2364/CDV from 2025.
The final text was not published as of 6 October 2026.
Name the edition in the EPC contract and the commissioning procedure. If the new edition lands mid-project, the contract decides which one governs.
Category 1 vs Category 2: which test regime applies?
Category 1 applies to all systems. Category 2 is an extended regime that adds I-V curve testing. Clause 5.3.6 lists further optional tests, such as infrared scans.
| Test | Category 1 | Category 2 | What it catches |
|---|---|---|---|
| Continuity of protective earthing and equipotential bonding | Yes | Yes | Open or loose earth paths |
| Polarity | Yes | Yes | Reversed strings before they meet the inverter |
| PV string combiner box test | Yes | Yes | Wrong string landing, blown fuses |
| String or HSA open-circuit voltage | Yes | Yes | Missing modules, wrong string length |
| String or HSA current (short circuit or operational) | Yes | Yes | Faults, shading, damaged modules |
| Functional tests | Yes | Yes | Switchgear, inverter, protection operation |
| Insulation resistance of DC circuits | Yes | Yes | Damaged cable insulation, wet connectors |
| String or HSA I-V curve | No | Yes | Mismatch, degraded modules, bypass diode faults |
| Infrared thermography | Optional | Optional | Hot spots, failed connections |
HSA means harness sub-array: a group of strings joined in parallel by a string wiring harness. Amendment 1 added the term and rewrote the Category 1 list to say “string or HSA” for the voltage and current tests.
How do you choose the category?
The standard does not tie category to a capacity threshold. The owner, lender, or tender usually decides. Use this as a starting rule:
| Project situation | Suggested regime | Reason |
|---|---|---|
| Small rooftop, owner-funded | Category 1 | Proves safe installation at low cost |
| C&I rooftop with a generation guarantee | Category 1 plus I-V on a sample | Gives a performance baseline for disputes |
| Utility-scale or lender-financed plant | Category 2 | Every string gets a recorded I-V baseline |
| Plant with suspected module damage | Category 2 plus thermography or EL imaging | Finds defects a Voc test misses |
This table is our engineering suggestion, not a clause of the standard. Confirm the regime in the contract, the tender, or the lender’s technical requirements.
What are the pass criteria for string tests?
Amendment 1 sets clear bands for current and I-V results. These come from the published amendment text, clauses 6.5 and 7.2.
| Check | Comparison basis | Typical pass band |
|---|---|---|
| String or HSA short-circuit current | Calculated expected value, corrected to measured irradiance | Within ±10% |
| String or HSA short-circuit current | Adjacent identical string, stable irradiance | Within ±10% of average |
| Operational string current | Adjacent string or calculated value | Same as above |
| I-V curves of identical strings | Maximum vs minimum curve | Within 10% |
| I-V array performance check | Plane-of-array irradiance | At least 400 W/m2, stable |
The amendment states that the short-circuit current test detects faults. It is not a performance measurement. Performance belongs to the Category 2 I-V test.
What if the sky will not cooperate?
Clouds break the comparison. The amendment allows three fixes: delay the test, re-run it later, or use two meters with one on a reference string. Simultaneous readings should then agree within ±10%.
For operational tests, it also allows an irradiance meter correction, a PV test meter with irradiance input, or an I-V curve test.
How should Voc be checked?
Compare each string’s measured open-circuit voltage with the expected value at the measured cell temperature. Compare identical strings with each other too. A string one module short reads about one module’s Voc low, which a careful tester will spot.
What does the insulation resistance test require?
Insulation resistance is tested on the DC circuits with a test voltage set by system voltage. Amendment 1 changed Table 2 for arrays up to 10 kWp. It relabelled the top band as 500 to 1,000 V and added a new row.
| System voltage | Test voltage | Minimum resistance |
|---|---|---|
| Above 1,000 V (new row in AMD1) | 1,500 V | 1 MΩ |
Read the full Table 2 in the standard for the lower bands.
For arrays above 10 kWp, Method A tests strings or combined strings. Method B tests the whole array or sub-array first. If Method B fails, test subsections with Method A.
Insulation testing on a live array is hazardous. Follow the procedure in the standard, isolate the circuit, and use rated test equipment.
How should I-V curve testing be run?
Run it on each string or HSA under stable sun. The circuit under test is isolated and connected to the I-V tracer. Results are corrected to standard conditions using IEC 60891.
A clean I-V curve shows the expected shape. Steps in the curve point to shading, cell cracks, or a bypass diode carrying current. A low fill factor points to series resistance, such as a poor connector.
Keep the raw curve files, not only a summary table. A later warranty claim needs the curve, the irradiance, and the module temperature at test time.
Where does thermography fit?
Infrared scans are optional under 62446-1. When the owner wants them, IEC TS 62446-3 sets the method: equipment, ambient conditions, procedure, and reporting. Our note on IR thermography covers what a scan finds.
What goes in the IEC 62446 handover file?
The standard requires copies of all test and commissioning data. At minimum, that means the verification results from clauses 5 to 9. Annexes A to C give model forms for verification, inspection, and test reports.
A complete handover file usually holds:
- System data: rated power, module and inverter models, installation dates, and the designer and installer.
- Wiring diagram showing array layout, string configuration, cable sizes, and protection devices.
- Datasheets for modules, inverters, and other key components.
- Mechanical design information for the mounting structure.
- Operation and maintenance information, including emergency shutdown.
- Test results and the inspection report, signed and dated.
Annex B now references IEC 62548:2016 rather than the 2013 technical specification. Make sure your inspection checklist cites the current edition.
Drawings that match the installed system are the part most often missing. Our post-design engineering service produces as-built single-line diagrams and string schedules that a test team can work from.
Common acceptance testing mistakes
These are the issues that most often weaken a commissioning record:
- Testing against the datasheet at STC. Expected current must be corrected to measured irradiance. Raw datasheet values fail good strings.
- No irradiance record. A current reading without a matching irradiance reading cannot be defended later.
- Summary sheets only. Keep raw meter exports and I-V files with timestamps.
- String IDs that do not match drawings. If the test sheet says S-14 and the drawing says INV2-S3, the record is weak.
- Unstated edition. “Tested per IEC 62446” without an edition invites argument.
How does this connect to performance monitoring?
Acceptance testing proves the plant was built right on day one. Ongoing performance is measured under IEC 61724. Amendment 1 points readers to IEC TS 61724-2 for system performance assessment.
Our guide to IEC 61724 performance monitoring covers sensor classes and the performance ratio. A Category 2 I-V baseline makes later degradation claims under the PV failure modes guide much easier to prove.
FAQ
Is IEC 62446 mandatory?
Not by itself. It becomes binding when a contract, tender, lender, or national rule calls it up. Check the project documents and the local authority’s requirements.
Does IEC 62446-1 apply to off-grid systems?
No. Part 1 covers grid-connected systems. IEC 62446-2 on maintenance also excludes off-grid systems and systems with batteries.
Can module-level power electronics systems be I-V tested?
Often not at string level. The amendment notes that I-V and EL tests are usually not possible on such systems. Module-level data can be used to find problems instead.
Who should perform the tests?
A competent person with rated equipment, following the procedure in the standard. Many owners appoint an independent engineer to witness Category 2 tests on financed plants.
Get the drawings your test team needs
Acceptance testing goes faster when string schedules, SLDs, and as-built layouts agree. Heaven Designs prepares execution drawings for rooftop and ground-mount projects.
To scope drawings for a plant heading into commissioning, request a project quote. We reply within 1 business day.