Solar PV Commissioning Checklist: IEC 62446-1 Tests

Commissioning a grid-connected solar PV system means proving the installation matches the design and is safe before it is energised. IEC 62446-1 sets out the documents, inspection and tests: polarity, string voltage and current, insulation resistance and earthing. This guide gives the order, a cold-day string sum and a filled test record.

One fact about our own offer, so you can judge this fairly. The EDWartens solar and EV charging engineer job simulation is a training project at a simulated company, done day by day with project documents, emails and tickets. It is not employment, an internship or a work placement. The first week is free and every ticket is checked as you hand it in. A graded, verifiable certificate is optional, and the longer Premium version is paid; prices show in your own currency before you pay. It shows on your EDWartens profile under Work experience, marked as a job simulation.

Safety first. Testing a live PV array involves direct current that cannot be switched off while the sun shines. Only competent people, with the right instruments, permits and procedures, should do it. This guide teaches the logic of the records and is not instruction for working on a live system. Read the HSE guidance on electricity at work if you work in Great Britain.

What does IEC 62446-1 cover?

The standard covers grid-connected PV systems. It says what information must be handed over, what an installer inspects, which tests to carry out and how to record them. It does not replace national wiring rules or the network operator's requirements, and a system with batteries needs more than this document alone. The IEC page for the standard lists the published edition. At the time of writing, in October 2026, the edition on sale is the 2016 one, with an amendment from 2018, and a revision is in preparation. Editions change, so check which one your client's specification names before you build a record around it.

The standard is protected by copyright and is not free to read. This guide describes the steps in our own words and does not reproduce its text or tables. Use a licensed copy for the exact limits.

Documents to hand over

A system is not finished when it works. The client needs the paper that proves what was built. A typical handover pack holds:

Before you test: check the design sum

Testing proves the installation matches the design, so first check the design is sound. The classic sum is how many modules go in a string. Here is a worked example with invented module and inverter data.

The temperature rise from the standard 25 degrees C to minus 5 degrees C is 30 K. The cold-day Voc of one module is:

37.2 V x (1 + 0.0029 x 30) = 37.2 V x 1.087 = 40.44 V.

Divide the limit by that figure: 1,045 V / 40.44 V = 25.8 modules. Round down, which gives a maximum of 25. A designer who picks 24 modules leaves a small margin for tolerance. Check the other end too, because 26 modules would give 1,051 V on a cold morning. That is below the 1,100 V rating but above the chosen design limit, so it fails. Then check the other direction: in summer heat the string voltage falls, and it must stay above the inverter's start-up and tracking minimum. A string that is fine in winter and drops out in July is a common finding.

The test sequence

The order matters because each test assumes the one before it passed. The sequence below paraphrases the structure of the standard and the usual practice. Your copy of the standard has the exact requirements.

The standard also describes extra tests, such as a full current-voltage curve and infrared imaging, that some clients ask for. They add information on module health but are not a substitute for the basic set above.

A filled string test record

Here is an invented record for an array of eight strings, each of 24 of the modules above. Conditions on the day: back-of-module temperature 22 degrees C, irradiance 640 W/m2 from a reference cell, steady for the whole set.

First work out what to expect. Open-circuit voltage: one module at 22 degrees C is 37.2 V x (1 + 0.0029 x 3), which gives 37.52 V, and 24 modules give about 900.6 V. Short-circuit current scales with light: 10.9 A x 640 / 1,000 = 6.98 A. The record uses a plus or minus 2 percent window on voltage (882.6 to 918.6 V) and plus or minus 5 percent on current (6.63 to 7.33 A), invented limits for this example. Your client's specification sets the real ones.

Three strings need a decision, and each tells a different story.

S4, voltage low. The reading is 37.6 V under the 900.6 V expectation. That is almost exactly one module. Before any theory, count the modules in the string and compare with the layout drawing. The likely finding is a missing or bypassed module or a loose connection, and the fix is physical, not a recalculation. A single module with a failed bypass diode would drop the voltage by about a third of a module, which is not what the reading shows.

S5, insulation low after rain began. The reading of 0.38 megohms is far below what the other strings show and under the limit for this system. Record the conditions. Do not sign it off because it is raining, and do not condemn the string on the first reading either. Re-test when dry. In this invented case, the dry retest the next morning gives 24 megohms after a wet connector was dried and re-seated. Both readings stay in the record with the cause and the action, which is far stronger evidence than a single clean number.

S8, current low. 5.2 A is about 25 percent under the 6.98 A expectation, while the voltage is right. That pattern points to shading, soiling, a cracked or mismatched module, or a poor connection, not a missing module. Check the reference cell, look for shadows from roof equipment, inspect the connectors and consider an infrared check. Retest when conditions are steady and write the cause in the record.

The skill the record tests is not arithmetic. It is the habit of comparing every reading with an expectation you worked out first, and refusing to mark a result as passed because it is probably fine.

Safe energising: a checklist

• All test results recorded with date, instrument, conditions and the name of the tester.
• Every hold from the record closed out, with the retest result next to it.
• DC and AC isolators labelled and working, with warning labels in place.
• Earthing and bonding confirmed against the single-line diagram.
• Polarity confirmed on every string before any inverter connection.
• Inverter settings, protection and export limits checked against the approved connection.
• Cable routes, glands and fire barriers inspected and sealed.
• Emergency shutdown information visible at the main supply and the inverter.
• Roof access and fall protection controlled, and no one working under test.
• Network operator notification or approval confirmed as required.
• Lockout and tag procedure used for any work after the first test.
• Handover pack complete and a copy given to the client.

Grid connection: G98 and G99, and other regions

In Great Britain, generators connect under the Energy Networks Association's procedures. Generation of up to 16 A per phase usually follows G98, with notification after installation, and larger generation follows G99, which needs approval from the network operator first. Documents are updated, so check the Energy Networks Association for the current version. India and Gulf states have their own utility rules and standards, set by regulators and utilities, with policy from bodies such as the Ministry of New and Renewable Energy. The IEA PVPS programme publishes international reports on PV systems. Never assume a rule from one country applies in another.

Adding EV chargers on a limited supply

Chargers often join the same site after the PV is built, and the supply is the limit. Take an invented example: a site with a 100 A per phase supply and a base load that peaks at 38 A per phase, wanting four 22 kW chargers (32 A per phase each). Together they could draw 128 A, far above the 62 A of headroom (100 A less 38 A). Without management the main fuse would trip or the supply would be overloaded.

A load management controller shares the headroom. With the base load at its peak, the four chargers share 62 A, which is 15.5 A each, about 10.7 kW on a 400 V three-phase supply. When the base load drops to 20 A, the headroom is 80 A and each gets 20 A. The rule is simple: the controller measures the site load, subtracts it from the supply limit, divides the rest among the active chargers and never goes below the minimum current an electric vehicle accepts, which is 6 A. Four chargers at 15.5 A is comfortably above that. Our post on the solar and EV charger commissioning simulator shows how this looks in a lab.

Practise it

To practise the sequence, sums and records with feedback, try the solar and EV charging engineer job simulation. It is a project at a simulated company, with design checks, a test record and a connection application. The electrical design engineer simulation, the substation and motor control centre engineer simulation and the maintenance electrical engineer simulation cover the neighbouring skills, and all sit on the job simulation hub.

For hands-on practice, the solar and EV charger simulator and the substation and motor control centre simulator are in the EDWartens lab, and the multimeter simulator lets you practise reading instruments. For isolation practice, read our guide to safe isolation procedure, and for the wider field, our post on renewable energy automation with PLC and SCADA. Our free courses on electrical fundamentals for technicians and industrial motor control build the basics.

A finished simulation shows on your EDWartens profile under Work experience, marked as a job simulation, and the optional certificate has a public page where anyone can verify it. The electrical design internship is a free guided four-week option, and the jobs board lists current openings.

Last updated 19 October 2026. All figures in the worked examples are invented. Edition status, limits and utility rules change, so work from the current documents.

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