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Straight answers about the issues that come up most often during commissioning, troubleshooting and routine O&M work on distributed PV plants.
Start by measuring each string voltage at the combiner box with the inverter isolated. A difference of more than 5% between strings on the same MPPT usually points to a mismatch. Then check for shading patterns, a faulty module or a loose DC connector before you assume the inverter is at fault. Log the readings so you have a baseline for the next trip.
For most distributed installations under 1 MW, the key documents are the grid connection application, the protection settings report and the commissioning test results. The utility wants to see that your anti-islanding protection and over/under voltage relays are set correctly and tested. Municipal approval paperwork is separate but often holds up the process longer than the technical work.
At least once a year for plants in good condition, but more frequently if you have had loose connection issues or if the site has high ambient temperatures. Scan under load, ideally when irradiance is above 600 W/m², so hot spots are actually visible. Pay attention to the DC fuse holders and lug connections, not just the main lugs, since those are where resistance tends to build up.
Morning dew on the rear side of bifacial modules can cause uneven soiling that is hard to see from the ground. The rear surface collects moisture and dust differently than the front, so you get a temporary current drop until the dew burns off. If the pattern repeats daily, check whether the mounting height is sufficient for airflow under the array. A simple cleaning test on one string will tell you if soiling is the issue.
Follow the lockout-tagout procedure exactly as written in your site's health and safety plan. Open the DC isolator, verify zero voltage with a rated tester, and wait the manufacturer's specified time for capacitor discharge. Do not rely on the inverter display alone, and always wear the correct PPE for DC arc flash. If you are unsure about the switchgear rating, treat it as live until proven otherwise.
Use a weather station on site, not regional satellite data, and log at five-minute intervals. Record both the AC energy and the DC input data separately so you can see where losses are occurring. Keep the raw files and the analysis in the same folder, and note any downtime or curtailment events in the log. Without that context, a performance ratio dip can look like a module fault when it was actually a grid outage.
Need a deeper look at a specific fault or compliance issue? Browse the technical resources or send us the details of your site.
We keep a record of the feedback we get from facility managers and EPC contractors. These are notes from real commissioning and troubleshooting jobs, not polished marketing lines.
Facility Manager, Mpumalanga
"The team helped us clear a persistent inverter fault that had been tripping our string combiner for weeks. They walked us through the DC bus voltage checks over the phone, and we found a loose connection in the combiner box that our own crew had missed. The fault log they sent afterwards was clear enough for our maintenance file."
Commissioning support, 2.4 MW ground mount
EPC Project Engineer, Western Cape
"We brought them in for a string sizing review on a bifacial array at altitude. Their checklist caught a voltage rise issue on cold mornings that would have pushed the inverter over its limit. They also flagged how albedo from the surrounding soil could increase rear-side current more than we had accounted for. That saved us a costly redesign after installation."
Design review, 850 kW commercial rooftop
Plant Operator, Northern Cape
"Their field notes on soiling losses gave us a practical way to measure when cleaning is actually needed, instead of sticking to a fixed schedule. We compared cleaned and uncleaned string performance over two months and adjusted our routine. The data logging template they shared made it straightforward to track performance ratio properly."
O&M support, 5 MW tracking array
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