Dynamic behaviour of a Francis turbine during voltage regulation in the electrical power system
Bibliographic record
Abstract
Hydroelectric units can be operated in synchronous condenser mode to provide reactive power to the electrical power system (EPS) for voltage regulation. In this operating mode, the hydraulic turbine consumes active power and in case of hydroelectric units equipped with a Francis turbine, pressurized air is injected in the draft tube to decrease the tailwater level below the runner for decreasing the friction losses. Several dynamic phenomena have been recorded during full-scale hydraulic turbine operation due to the air–water mixing causing pressure and torque fluctuations which may compromise the operation and safety of both the hydraulic machine and the EPS. In this paper, the study of the dynamic response of a Francis turbine prototype during synchronous condenser mode operation is performed to evaluate the transposition of the machine behaviour from the homologous reduced scale model to the full-scale prototype. Measurements of the pressure in draft tube cone, machine vibrations, and torque are performed in both full scale prototype and reduced scale model. The analysis of the dynamic behaviour of the hydraulic turbine focuses on the critical vibrations and power fluctuations. The onset of a sloshing wave in the draft tube cone is highlighted as predicted by the reduced scale model tests. Rotor–stator interactions (RSI) are analyzed and compared to the RSI during generating mode operation. The advantages of decreasing the pressure in the vaneless gap between the runner blades and the closed guide vanes by installing a draining pipe are emphasized to limit the amplitude of the fluctuations and to avoid unwanted two-phase flow phenomena in the vaneless gap which can perturb the machine operation and safety.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".