Designing Overhead Transmission Lines to Withstand Snow Avalanches
Bibliographic record
Abstract
The province of British Columbia, Canada, is prone to snow avalanches in its mountainous regions. Overhead transmission lines are often built along mountain sides and may trespass avalanche zones. From time to time, damages to transmission lines are observed due to avalanche impacts. The most phenomenal case was observed on a tangent structure of a 287kV transmission line located in the Northwest of British Columbia. Since its service in late 1960s, damages have occurred to the same structure four times in 1977, 1989, 2007, and 2018, respectively. The last one occurred on April 02, 2018, that destroyed the self-supported lattice tower. A temporary lattice tower had to be installed as an emergency response to restore the power supply as soon as possible. Driven by the 2018 incident, a systematic investigation was carried out to mitigate the avalanche impact on this power line. As a result, a rational design methodology was developed and implemented in this project. This paper is intended to describe the details of the design methodology. First, the phenomena of a snow avalanche are described. Second, design avalanches are established. Semi-empirical equations are recommended to determine the key parameters of a design avalanche. Third, the method of applying avalanche load on a power line and the ensuing structural analysis of the entire section of a transmission line consisting of towers, foundations, conductors, insulators, etc. is illustrated using the above-mentioned project as the case study. As a result of lesson and learn, the following principles are recommended to mitigate damage from avalanches effectively: (a) Conductors and structures shall be located away from an avalanche zone if feasible. Conductors shall be located high enough from ground to minimize the avalanche impact. (b) Conductors and structures shall have minimized area facing the avalanche to minimize avalanche impact, if feasible. (c) Various components in a transmission line shall be properly coordinated in terms of their relative strengths to minimize the consequences of avalanche induced failures if it occurs.
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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 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".