Experience with ISO-Paraffinic Insulating Oil for Power Transformers
Bibliographic record
Abstract
For many years Manitoba Hydro had used naphthenic oil refined by solvent extraction and hydrogen treatment in its power transformers. The oil purchased in 1960 through 1979 contained no more than 0.08% oxidation inhibitor. By 1990 naphthenic oil was specified as having at least 0.15% and not more than 0.4% oxidation inhibitor. However, during the 1990s insulating oil meeting this description experienced premature ageing under conditions of service. This resulted in the need to reclaim using Fuller's Earth or replace with new the oil in a number of large generator step-up transformers after less than 10 years of service. The unsatisfactory experience caused us to evaluate more reliable sources of insulating oil. Since 1999 Manitoba Hydro has used a synthesized iso-paraffinic insulating oil in new generator step-up, HVDC converter, and transmission transformers. This choice was made as a result of the improved oxidation stability and heat transfer capabilities of this fluid. In addition, the selected iso-paraffinic oil has low kinematic viscosity at -40°C which is a vital requirement in our climate. As many of these transformers installed since 1999 have been in service for at least 10 years, this paper tracks the results of insulating oil quality tests on typical units based on measurements of colour, interfacial tension, acidity, and dissipation factor. Other diagnostic tests involving the oil have included dielectric strength, water content, dissolved gas-in-oil and furan-in-oil. Manitoba Hydro participated in thermal ageing tests sponsored by CEATI on a number of small transformers filled with two types of naphthenic oil as well as the iso-paraffinic oil. These tests confirmed the superior performance of the iso-paraffinic oil compared to that of a commonly used naphthenic oil.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.002 |
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 source (direct Gemma or distilled Codex), 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".