Guide for Generator Condition Assessment In Hydropower Plant

Metrics for Generator Condition Assessment

For generator condition assessment, it is recognized that the physical condition cannot be properly and sufficiently evaulated based on the visual inspections only while the results from some routine or available tests are more critical as indication of generator condition.

Thus, as listed in Table 1, the following eight condition parameters are considered for condition assessment of generator and generator parts:

1. The Visual Condition
2. The Age
3. The Installed Technology Level
4. The Operating Restrictions
5. Stator Electrical Tests
6. Rotor Electrical Tests
7. Stator Core Tests
8. The Maintenance Requirement

These 8 condition parameters are scored based on the following: previous testing and measurements, historical O&M records, original design drawings, previous rehabilitation feasibility study reports if conducted, interviews with plant staff, and some limited inspections or previous inspections.

Table 1: Typical Generator Condition Assessment & Scoring

It is noticed that there are certain level of relevance between the age and physical condition, maintenance needs, or some operating restrictions.

However, as a benchmarking condition assessment without specific new testing and measurements conducted on site, these eight parameters are regarded as providing the basis for assessing the condition of generator parts and entire generator. If any type of tests or metrics are not applicable for some parts (e.g., the Stator Eletrcial Tests are only applicable to the Stator), input “NA” into the cells of irrelevant parts for this metrics.

In addition, the Data Quality Indicator, as an independent metrics, is to reflect the quality of available information and the confidence on the information used for the condition assessment. In some cases, data may be missing, out-of-date, or of questionable integrity, and any of these situations could affect the results of condition assessment.

The scores of data quality are determined by the on-site evaluators for each assessed part/item to indicate the data availability, integrity and accuracy and the confidence on the given condition ratings (MWH 2010).