Unity AI Insights: Classification Flag for Wind Turbines - Classification Logic

In this article:

• Introduction
• High-Level Logic
• Classes & summary of logic
  • Data Quality Control & Imputation
    • Missing or invalid inputs (flag value -1)
    • Data Outside Evaluation Limits (flag value 3)
  • External limitations
    • Utility Curtailment (flag value 1)
    • Overdesign: 11
  • Downtimes
    • Site Down (flag value 9)
    • Turbine Down (flag value 8)
    • Downtime Icing (flag value 7)
  • Degradations
    • Derate (flag value 5)
    • Degraded Icing (flag value 6)
    • Degraded Unknown (flag value 10)
  • Other 
    • Uprated or Overpower (flag value 2)
    • Nacelle Wind Speed Anomaly (flag value 4)
  • Default (in absence of other classification)
    • Full Performance (flag value 0)
• Priority Ranking System

Introduction

This page provides a summary of the logic behind the different classifications of the Classification Flag and is a complement to Unity AI Insights: Classification Flag for Wind Turbines.

High-Level Logic

The classification follows a hierarchical approach:

1. Data Quality Control: Unreliable data is flagged

2. Data Imputation: As some inputs are optional, some missing values can be filled using defaults or logical relationships

3. Classification: The classifications are simple rule-based logic. All rules are applied to every single data interval, resulting in several possible classifications per interval.

4. Prioritization/Ranking: The final classification keeps only the most highly-ranked class from all possible classifications, at each interval, resulting in a single classification per interval.

Classes & summary of logic

Data Quality Control & Imputation

Missing or invalid inputs (flag value -1)

• Logic: Identifies intervals where mandatory data is missing or unreliable (ActivePower, WindSpeedAdjusted, ActivePowerExpected) 

• Purpose: Properly classify intervals that cannot be reliably analyzed

Data Outside Evaluation Limits (flag value 3)

• Logic: Operating conditions outside reliable analysis range - very high wind speeds or very low power production

• Purpose: Properly classify intervals that cannot be reliably analyzed

External limitations

Utility Curtailment (flag value 1)

• Logic: Based directly on the Curtailment flag (see Unity APM: Curtailment Flag)

• Purpose: Identifies periods where turbine performance is externally constrained with expected losses at the generator level

Overdesign: 11

• Logic: ActivePowerExpected is below ActivePowerExpectedAsBuilt while still producing substantial power 

• Purpose: Identifies wind farm-level limitations due to grid constraints

Downtimes

Site Down (flag value 9)

• Logic: Entire site offline with negligible power production despite wind availability

• Purpose: Distinguishes site-wide outages from individual turbine outages or issues

Turbine Down (flag value 8)

• Logic: Individual turbine producing minimal power despite adequate wind conditions

• Purpose: Identifies complete turbine outages

Downtime Icing (flag value 7)

• Logic: Turbine downtime coinciding with PossibleIcingFlag 

• Purpose: Attributes downtime to ice accumulation on blades/sensors

Degradations

Derate (flag value 5)

• Logic: Consistent power production below expected levels with very little variation in power output for a defined rolling window (40 minutes). To assess that production is below expected levels, a threshold is based either on: 

  • Active Power Expected - Lower Control Limit, or

  • Performance Index  if Lower Control Limit is not available

• Purpose: Identifies intentional power limitations or control system constraints

Degraded Icing (flag value 6)

• Logic: Reduced performance coinciding with PossibleIcingFlag, for a certain rolling window (40 minutes). To assess that production is below expected levels, a threshold is based either on: 

  • Active Power Expected - Lower Control Limit, or

  • Performance Index if Lower Control Limit is not available

• Purpose: Identifies potentially ice-related performance degradation

Degraded Unknown (flag value 10)

• Logic: Power production below expected levels without clear cause. To assess that production is below expected levels, a threshold is based either on: 

  • Active Power Expected - Lower Control Limit, or

  • Performance Index if Lower Control Limit is not available

• Purpose: Catch-all for various degradation modes

Other 

Uprated or Overpower (flag value 2)

• Logic: Active power exceeds rated capacity by tolerance factor 

• Purpose: Detects turbine upgrades or temporary overpower conditions

Nacelle Wind Speed Anomaly (flag value 4)

• Logic: Power production significantly above expected levels for a certain window (at least 60  min) for given wind conditions. To determine abnormal conditions, a threshold is based either on: 

  • Active Power Expected - Upper Control Limit, or

  • Performance Index  if Upper Control Limit is not available

• Purpose: Detects anemometer issues or measurement errors and periods where wind-dependent KPIs will be erroneous

Default (in absence of other classification)

Full Performance (flag value 0)

• Logic: No other classification flags triggered

• Purpose: Normal operation within expected parameters

Priority Ranking System

The system uses a priority ranking. The order is defined as follows, from highest to lowest priority. It ensures that more specific or critical classifications win over less specific or less critical ones.