Field testing, modelling and analysis of ferroresonance in a high voltage power system
Bibliographic record
Abstract
Catastrophic equipment failures continue to occur today due to ferroresonance even though this phenomenon has been extensively studied over the past ninety years. This thesis is concerned with the tasks of defining where ferroresonance problems can exist in a high voltage power system, of determining methods for displaying safety margins between nonferroresonant and ferroresonant operating regions and improving upon existing ferroresonance simulation techniques. Several different ferroresonant circuits have been modelled and compared with field measurements taken on the Manitoba Hydro 230-kV power system or compared with laboratory measurements including: a de-energized transformer connected to the grading capacitance of an open circuit breaker, a transformer-terminated doublecircuit transmission line and a coupling capacitor voltage transformer. In a high voltage power system, the most prevalent ferroresonance circuit occurs between a de-energized transformer and the grading capacitor of an open circuit breaker. Experimental work has shown that losses in a pr ctical transformer are much larger during ferroresonance oscillation modes than predicted by conventional modelling techniques. A simple switched eddy-current loss resistor is found able to model the losses during subharmonic and fundamental frequency ferroresonance in a laboratory transformer. A major contribution of this work is a new method of visualizing the margin between nonferroresonant and ferroresonant states in a transformer/grading capacitor circuit has been developed. A general set of averaged equations is derived that permit the analysis of an nth order polynomial approximation of the magnetization curve. The location of the saddle points and slope of the stable manifold through the saddle points can be determined for a particular transformer under study. The Limacon of Pascal is found to be a good approximation to the geometric shape of the basin of attraction of the period-1 ferroresonant attractor and can be calculated using the saddle point location and slope of the stable manifold. The critical parameters resulting in a crossing of the separatrix can then be found by iteratively solving the Limacon equations. The new method will assist utility engineers in quickly assessing the potential risk of ferroresonance in their power system.
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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 | 0.000 |
| 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".