Investigation and diagnosis of a 184-MVA air-cooled generator heavily affected by slot partial discharge activity
Bibliographic record
Abstract
For many years, partial discharge (PD) activity has been used in air-cooled generators as one of the important indicators of degradation mechanisms in stator winding insulation. Up to a certain level, these degradation processes are slow. Under normal operation, PD measurement and trending can generally indicate that not only electrical but also mechanical, thermal or ambient (contamination) degradation processes are occurring. Partial discharge activity in air-cooled generators also produces ozone so that the presence of ozone inside and around the generator enclosure is indicative of PD activity. In some cases, the ozone concentration produced by sustained PD activity can reach such levels that it becomes a health hazard for plant personnel. Hazardous levels were recorded in 1991, after 12 years of operation, inside the enclosure of the four 184-MVA hydro generators at BC hydro's peace canyon (PCN) generating station, revealing a situation that was probably active for some years. Results from annual PD measurement performed using PDA (partial discharge analysis) techniques showed an asymmetry in favor of positive discharges that can be the result of slot discharges. Phase resolved partial discharge (PRPD) measurements combined with ozone measurements taken all around the rear perimeter of the generator core were used to confirm the nature of the PDs. Since one of the generators was scheduled for a complete stator winding and core replacement in 2006, an exhaustive investigation was performed before and after replacing the stator. Some stator bars were removed from the slots for visual inspection and extensive laboratory testing. This paper presents results of the on-line PD and ozone measurements, together with findings from visual inspection and laboratory investigations of the retrieved bars. These results were analyzed collectively in order to establish the root cause of the insulation problem as well as the deterioration mechanism of the generator stator winding. Finally, a new pre-installation testing procedure is recommended to prevent such a costly insulation problem from occurring again.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".