Load tap changers: investigations of contacts, contact wear and contact coking
Bibliographic record
Abstract
The Electrical Power Research Institute (EPRI) and BC Hydro (British Columbia, Canada) sponsored a project on improving the maintenance of "on-load tap changers" (LTC). The investigation of contacts focused on stationary reversing switch assemblies (Part 1) and diverter switch contacts (Part 2). For the study of reversing switch assemblies BC Hydro provided an LTC for an in-house "case study" and the actual study lasted about nine months. The objective of this study was the evaluation of stationary reversing switch assemblies and their performance under different current loadings. Resistance, load and operating temperatures were investigated. This work compared the performance of three assemblies, two were new and one was old. The new reversing switch assemblies were made of either copper or of silver alloy (and silver-plated components), while the third, used brass assembly came with the load tap-changer (Part 1). Powertech Labs Inc. conducted in cooperation with BC Hydro, among other investigations, the study of diverter switch contacts of an LTC ("Kent" case study) at one of the utility's substations. This study lasted for nearly one year and addressed transformer oil chemistry, gas evolution and contact performance under conditions of accelerated switch operations (reported elsewhere). In addition various LTC contacts from several substations were assessed. These investigations emphasize the importance of quality control and quality assurance, especially for arcing contacts of the copper infused tungsten type (Part 2).
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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 | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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 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".