3801 SMA — String Mismatch / Low Power
At a glance
- Severity
- WARNING
- Domain
- DC_SIDE
- Reference standard
- IEC 62446-1 / IEC 61724-1
- Product / context
- String Current Deviation
What it means
One or more strings produce significantly lower current or power compared to the others, causing an overall plant yield loss. Typical causes include partial shading, degraded modules, faulty bypass diodes, or hotspots.
Probable causes
- Partial shading from vegetation, dirt, or nearby structures.
- Bypass diode short-circuited or open inside the module junction box.
- Modules with cracked cells (microcracks) reducing string current.
- Active hotspot on one or more modules due to thermal mismatch.
Where to start
Access the inverter monitoring and compare the currents of all strings connected to the same MPPT. Is there a string with current more than 15% below the average of the others?
Full guided diagnosis in the app
The diagnostic tree for this fault has 9 guided steps with measurements, checks and resolutions. You'll find it in ElectraIQ, one of the five IndexOS apps: free, works offline.
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