Commissioning, testing, fault finding and maintenance
Commissioning and testing
IEC 62446-1 is the reference for PV system documentation, commissioning and testing. A typical sequence: visual inspection (labelling, connectors, cable support, earthing, IP ratings, clearances), protective earthing and bonding continuity, string polarity and open-circuit voltage, short-circuit or operating current with irradiance and module temperature recorded, insulation resistance of each string to earth, then functional checks of the inverter, AC protection, RCD and any export limitation. Record the results on an Electrical Installation Certificate with schedules, plus a commissioning record and handover pack. Commissioning data taken in poor light is of limited value - note the irradiance so the figures can be normalised.
Worked example - insulation resistance
Disconnect the inverter, short the string's positive and negative conductors together, then test between the shorted conductors and earth with a 1000 V DC insulation tester. IEC 62446-1 accepts a minimum of 1 MΩ per string, but healthy new arrays normally read far higher (tens of MΩ). A reading of, say, 0.4 MΩ indicates moisture ingress, cable damage or a failed connector - find it before energising.
Fault finding
Common faults include blown string fuses, open-circuit connectors, reverse polarity, failed bypass diodes and hot spots, earth insulation alarms, over-voltage trips caused by grid voltage rise, nuisance RCD tripping, and export-meter or CT errors. A string reading one module's Voc lower than its neighbours usually means an open circuit at that module or connector, not a failed module. Thermal imaging and I–V curve tracing speed up diagnosis.
Maintenance
Periodic inspection typically covers visual condition, connector and torque checks, inverter fans and filters, firmware, thermal imaging, earthing continuity and a repeat of key electrical tests.
Traps
Insulation testing with the inverter connected; accepting a reading taken in near-darkness without noting irradiance; blaming the inverter for a fault that is actually a loose MC4.