Solar Plant Commissioning Checklist for India (2026)

Direct Answer

Industrial solar commissioning in India follows the IEC 62446-1:2016+AMD1:2018 test regime: Category 1 tests on every system — earthing/bonding continuity, polarity, string open-circuit voltage, string current, functional tests and DC insulation-resistance (Megger) testing — plus Category 2 tests for larger C&I plants, namely I-V curve tracing and infrared thermography. Earthing is verified by the fall-of-potential (3-terminal) method at 40/50/60% spacings, targeting about 1 ohm and never above 5 ohms. Documentation then moves in sequence: approved SLD, layout and datasheets, Category 1 tests, Category 2 tests, CEIG (electrical inspector) approval, DISCOM-installed net and generation metering per CEA metering regulations, energisation, and the net-metering agreement.

TL;DR

• Category 1 tests are non-negotiable on every plant: continuity, polarity, Voc, string current, functional checks and DC insulation resistance.
• Category 2 separates serious C&I EPCs from the rest: I-V curves expose mismatch and series resistance; thermography catches hot cells and bad connections (needs 500 W/m² or more and clear skies).
• No energisation without the statutory chain: CEIG approval, then DISCOM-installed and sealed net + generation meters, then the net-metering agreement.

Why Commissioning Is Where Plants Are Won or Lost

Most industrial solar defects are invisible at energisation. A reversed string still makes power; a high-resistance connector generates fine, and cooks for a year. By the time these surface, the warranty clock and the plant's payback are both running against you — commissioning is the one chance to verify that the plant you paid for is the plant you received.

For factory owners and EPC buyers, this checklist is your acceptance instrument. Make it a contract deliverable: your EPC should sign against each item, with test records attached, before final payment milestones. Pair it with disciplined EPC selection and contract clauses that bind the vendor to these results.

Phase 1: Pre-Installation Documentation Review

Commissioning begins before the first module is bolted. Verify the design package exists and is internally consistent:

1. Approved single-line diagram (SLD) matching the as-built electrical configuration
2. Approved array layout drawings, string sizing calculations and cable schedules
3. Module, inverter and mounting-structure datasheets on record
4. Earthing and lightning protection design with earth pit locations
5. Structural adequacy report for the roof
6. DISCOM application and net-metering feasibility confirmed

Missing documents at this stage are a warning sign: a plant whose as-built SLD never existed cannot be safely operated, extended or insured later.

Phase 2: Category 1 Tests (Every System, No Exceptions)

IEC 62446-1:2016+AMD1:2018 defines Category 1 tests as the minimum verification applicable to every PV system, from a 10 kW rooftop to a 5 MW industrial plant:

Record every value, not just pass/fail. String Voc and current baselines from commissioning day are what your O&M team will compare against for the plant's whole life.

Phase 3: Category 2 Tests (Recommended for Larger C&I Plants)

For larger commercial and industrial installations, Category 2 tests verify performance quality that Category 1 cannot see:

1. I-V curve tracing. Tracing each string's current-voltage curve exposes mismatch, shading anomalies and elevated series resistance — a crimped connector shows up here long before it appears in generation data.
2. Infrared thermography. IR imaging of modules, connectors and terminations finds hot cells, failed bypass diodes and high-resistance joints. Conditions matter: thermography needs at least 500 W/m² and clear skies — schedule a clear mid-day slot, not a hazy winter afternoon.

Category 2 testing is worth every rupee above roughly the 100 kW class. Ask for the I-V traces and thermal images as deliverables — an EPC confident in its workmanship hands them over without being asked twice.

Phase 4: Earthing Verification by Fall of Potential

The earth system gets its own formal test. The fall-of-potential (3-terminal) method places potential and current electrodes at 40%, 50% and 60% spacings of the test distance; the plateau across readings is the earth resistance. The criterion is unchanged from design: target approximately 1 ohm, and earth resistance must never exceed 5 ohms. Test each pit separately and log values with weather and soil conditions.

Phase 5: Statutory Approvals and Metering

With tests complete, the statutory chain proceeds in fixed order — each step depends on the one before:

Two points industrial buyers frequently get wrong. First, CEIG approval is a genuine review with its own timeline — our CEIG approval guide walks through the inspector's checklist. Second, MNRE requires both a net meter and a generation meter, installed by the DISCOM — not the EPC. The generation meter substantiates generation records, and its sealing per CEA metering regulations must precede energisation. Coordinate the net-metering application early: DISCOM queues are the schedule item nobody's Gantt chart survives.

Phase 6: Handover Package

Before final payment, collect:

1. Complete IEC 62446-1 test records, with I-V traces and thermal images
2. Earth resistance reports per pit
3. As-built SLD, layout and cable schedules
4. CEIG approval letter and DISCOM meter-sealing records
5. Warranties registered — modules, inverters, structure — with claim procedures, per our warranty management guide
6. O&M plan and first preventive-maintenance schedule, including seasonal O&M best practices
7. Insurance policy active from day one — see insurance for industrial solar projects

A plant handed over without this package is not commissioned — it is merely switched on.

Frequently Asked Questions

What is the difference between Category 1 and Category 2 tests under IEC 62446-1?

Category 1 tests are the minimum required on every PV system: earthing/bonding continuity, polarity, string Voc, string current, functional tests and DC insulation-resistance testing. Category 2 tests — I-V curve tracing and infrared thermography — are recommended for larger C&I installations and reveal performance defects such as mismatch, elevated series resistance and hot cells that Category 1 cannot detect.

How is solar earthing resistance tested and what value must it be under?

By the fall-of-potential (3-terminal) method, with potential and current electrodes at 40/50/60% spacings of the test distance; the plateau across these readings is the earth resistance. The plant must target approximately 1 ohm and the resistance must never exceed 5 ohms.

Who installs the net meter and generation meter for an industrial solar plant?

The DISCOM installs and seals both meters, per MNRE requirements and CEA metering regulations. The EPC does not install them. The plant needs both a net meter (for export/import settlement) and a generation meter (for total generation records), and energisation must wait until metering is complete and sealed.

Can we energise the plant before CEIG approval?

No. CEIG (chief electrical inspector) approval is the statutory clearance to energise an industrial solar installation. Energising before inspection exposes the owner to penalties, disconnection orders and insurance complications, and it forfeits the safety assurance the inspection exists to provide.

What conditions are needed for IR thermography during commissioning?

Infrared thermography requires solar irradiance of at least 500 W/m² and clear skies for reliable results. Schedule it for a clear mid-day window; thermography taken in overcast or low-irradiance conditions misses genuine hot spots and produces false confidence.

What documents should be in the commissioning handover package?

At minimum: the complete IEC 62446-1 test records with I-V traces and thermal images, earth resistance reports per pit, as-built SLD and layout drawings, CEIG approval letter, DISCOM meter-sealing records, all registered warranties with claim procedures, the O&M plan, and an active insurance policy covering the plant from day one.