VIA created the Condition-Based Rating (CBR) system with the goal of providing GDAC™ members with a consistent way to assess the condition of all the transformers in their fleet. This rating provides a way to categorize the condition of a transformer with a scalable, measurement-based approach from regularly gathered inspection measurement data. Transformers are rated on a scale of 1 to 5, where a rating of 1 represents a transformer near end of life, or poor condition. A rating of 5 represents a transformer in very good condition.
The CBR is created by scoring each individual measurement from inspection data (such as dissolved gas analysis, oil measurements, age, and furan analysis), applying a relative weighting, and producing a single score of 0 to 100 for each transformer (also referred to as the Combined Score). This score is then categorized into a rating of 1 to 5 (the CBR).
Below is a flowchart to illustrate how the CBR is calculated.