Novasense Portal - anomaly detection
The Novasense Portal is designed to detect most common anomalies in solar plants. The anomaly detection works at its full potential for plants that meet the following requirements:
- Multiple strings in the same field (orientation), connected to multiple inverter MPPTs or monitored stringbox inputs.
- Up to 2 strings connected in parallel on a single MPPT / monitored stringbox input.
- No usage of module optimizers.
- AC voltage and frequency measurement available, in addition to mandatory DC (MPPT or stringbox) and AC power measurements.
- Absence of local shading sources.
- 6 months of historical data, covering both winter and summer months, with no vegetation shading or strong soiling.
In many situations, not all of these ideal requirements are fulfilled and it's perfectly fine as well. The table below show the anomaly detection time and eventual limitations for different plant configurations.
| Plant configuration | MPPT/Inverter outage | Grid outage | Single string failure | Single module failure | Snow coverage | Power limitation | Vegetation shading | Strong soiling |
|---|---|---|---|---|---|---|---|---|
  |  |  | |  |  | () / PR | () / PR | |
| According to ideal requirements above | 1 hour | 1 hour | 1 day | up to 1 week | 1 day | 1 day | 1 month (report) | 1 month (report) |
| Field with all string(s) on single MPPT | 1 hour | 1 hour | up to 1 week | up to 1 week | 1 day | 1 day | 1 month (report) | 1 month (report) |
| Single current measurement for 3..5 strings in // | 1 hour | 1 hour | up to 1 week | not guaranteed | 1 day | 1 day | 1 month (report) | 1 month (report) |
| Single current measurement for > 5 strings in // | 1 hour | 1 hour | not guaranteed | not available | 1 day | 1 day | 1 month (report) | 1 month (report) |
| Plant with module optimizers | 1 hour | 1 hour | not guaranteed | not available | 1 day | not available | 1 month (report) | 1 month (report) |
| Missing AC voltage/frequency data | 1 hour | detected as inverter outage | 1 day | up to 1 week | 1 day | 1 day | 1 month (report) | 1 month (report) |
| Impact from local shading sources | 1 hour | 1 hour | 1 day | not guaranteed | 1 day | not guaranteed | 1 month (report) | 1 month (report) |
| Vegetation or other irregularities during initial training period | 1 hour | 1 hour | 1 day | not guaranteed | 1 day | not guaranteed | 1 month (report) | 1 month (report) |
| Missing 6 months of training data | 1 hour | 1 hour | 1 day | not guaranteed | 1 day | not guaranteed | 1 month (report) | 1 month (report) |
Initial threshold tuning phase
An initial threshold tuning is performed by the Novasense staff after collecting approximately 6 months of operational data without any significant plant issues. This tuning can be done shortly after onboarding if historical data is already available in the data source. Before the initial threshold tuning, it is normal to observe performance-related anomalies, as the exact behavior of the plant is not yet known. After the initial threshold tuning, false positives may occur sporadically and are more likely during periods of very low irradiance. However, false positives should remain exceptional at this stage.
Underperformance detection and evaluation
The main focus of automatic anomaly detection is identifying sudden changes in a PV system, typically caused by defective components or major external factors that prevent the plant from operating normally. In some cases, slowly evolving external performance degradation factors, such as strong soiling or nearby vegetation shading, can trigger the detection of string underperformance. However, the sensitivity level of automatic detection may vary from plant to plant. Novasense recommends a systematic evaluation of the plant performance ratio to assess the need for corrective actions against these external factors.