Potential-induced degradation (PID)
High system voltage driving a recoverable — then permanent — power loss.
Potential-induced degradation (PID) is power loss caused by leakage currents between the cells and the grounded module frame under high system voltage, worsened by heat and humidity. It can strip 10–30% from affected modules, hits strings near the negative end of the array hardest, and is partly recoverable if caught early — making detection time-critical.
Symptoms
- Modules near the negative (high-potential-difference) end of strings underperform most.
- A gradual power decline across affected modules, accelerating in hot, humid conditions.
- Output partially recovering after dry spells or overnight, in early-stage PID.
SCADA signatures
- A systematic gradient in string performance correlated with electrical position in the array.
- Loss worsening with humidity and module temperature rather than tracking irradiance.
- Combiner-level PR drift concentrated on specific inverters/strings, not plant-wide.
Root cause
A high potential difference between cells and the grounded frame drives ion migration (notably sodium from the glass) into the cell, creating shunting leakage paths. Moisture and heat accelerate it. Transformerless inverters and certain module/grounding configurations are more exposed; anti-PID hardware and night-time recovery devices mitigate it.
Financial impact
PID can remove 10–30% from affected modules and, once advanced, becomes permanent. Across the worst-hit strings of a plant that is a large, compounding yield loss — but early detection plus PID-recovery measures can reclaim much of it, so the value is overwhelmingly in catching it early.
How NuraVolt detects it
NuraVolt looks for the tell-tale spatial gradient — underperformance correlated with electrical position and amplified by humidity and temperature rather than irradiance — to separate PID from soiling, shading, or diode faults, and flags it while recovery is still possible.
Frequently asked questions
See also
A string delivering less current than its peers under the same irradiance.
Falling insulation resistance on the DC side — a safety-critical fault.
Unequal power across the MPPT inputs of a single inverter.
PID loss is easier to see once the heat penalty is removed.
See this on your own plants
NuraVolt turns your SCADA and BMS data into early fault detection, degradation-aware BESS analytics, and audit-ready reporting. A fixed-scope audit shows you what we’d find on your portfolio.