Solar Lattice

DetectionMethod

Performance monitoring

ID
method:performance-monitoring
IRI
https://solarlattice.org/kb/method/performance-monitoring
Status
active
Also known as
Monitoring tools

Performance monitoring uses plant data from the monitoring system or SCADA to spot faults. It does this by finding electrical signatures, comparing current behavior with history or with a simulated system, and comparing components or subsystems with each other. Detection can rely on statistical tests, machine learning or programmed rules, and these approaches can be combined, for example by comparing the performance of neighboring arrays. The monitoring system should use open standards, have auditable measurement procedures, support calibration and backup, and collect enough data to report performance under the common industry standards. Monitoring can flag performance losses from junction box failures that create short or open circuits. It can also find inverter voltage floor losses, where DC voltage stays pinned near the inverter minimum while output is lower than irradiance would support. Irradiance-normalized string output helps find tracker twist. Compare rows in the morning, around solar noon and in the afternoon, because a twisted row can look fine at one position and lose output at another. Performance ratio trends, together with rain and cleaning records, help measure dust soiling. Early-life production trends, compared with nameplate values, help find light induced degradation. Before blaming a specific cause, filter out outages, curtailment, clipping, soiling and sensor faults. Do not rely on a single dirty irradiance sensor, because sensor drift or local obstruction can look like soiling. Monitoring only points to a likely cause. Confirm it in the field, for example with visual and infrared inspection of junction boxes or angle surveys of tracker rows, because several mechanical faults can produce similar production signatures.

<!-- review notes

Claims

produces

c1 verified · fact DC voltage pinned at minimum

Voltage-floor screening looks for intervals where inverter DC voltage sits at or near its minimum operating threshold while output supported by irradiance is lower than expected.

verified by: joshuahamsaverified on: 2026-10-19review note: support check: partial - Passages support screening for DC voltage near the minimum threshold with lower-than-expected output, but not the specific signals (high-temperature periods, normal POAI, model IDs).

c2 verified · fact Operating voltage above Vmp

Inverter operating voltage from SCADA is compared with array Vmp from in-situ IV sweeps or a temperature-corrected model. Operating power below the IV-derived Pmp supports a voltage-floor event.

verified by: joshuahamsaverified on: 2026-10-19review note: support check: partial - Passage supports comparing operating voltage to IV-derived Vmp and power below Pmp indicating voltage floor, but not the module temperature lowering Vmp or specific signals.

c3 verified · fact Low normalized row current

For tracker twist, the affected rows show lower irradiance-normalized current than neighboring rows. The shortfall depends on time of day and shows up at low sun angles, during backtracking transitions and in windy intervals.

verified by: joshuahamsaverified on: 2026-10-19

c4 verified · fact Declining performance ratio

For dust soiling, performance ratio trends and irradiance-normalized output are reviewed over dry accumulation periods together with rain and cleaning records.

verified by: joshuahamsaverified on: 2026-10-19review note: support check: partial - Passages say to compare performance ratio trends, rain and cleaning records, and normalized output over dry accumulation periods, but do not describe the gradual fall and recovery after rain/cleaning pattern explicitly.

c5 verified · fact Production loss alarm

Monitoring tools can flag a performance loss when a junction box failure creates a short-circuit or open-circuit condition.

verified by: joshuahamsaverified on: 2026-10-19review note: support check: partial - Passage says monitoring may detect performance loss from short/open-circuit junction box failures, but not the string current to zero or voltage step down signals.

Referenced by

Data