Research — Illustrative (draft, unvalidated)
Insulator swing chart — auto
The line angle at the structure sweeps from 0° to 5° while three curves show the minimum vertical span needed to hold the swing at each of the bulletin's TH-10 example limits. A sharper line angle adds sideways pull, so every curve climbs, and the wind cases climb from a much higher start.
Line angle at the structure
0°1° · bulletin's first worked point5°
Reading —
Required vertical span vs line angle · 800 ft horizontal span · dashed marks at the bulletin's 1° and 2° points
Required vertical span at this line angle
Line angle
Moderate-wind case
High-wind case
How the check read it
Client-side port:the logic and table in this page are a TypeScript port of the harness function, checked against values exported from the Python tests. Not a live API call. Domain maturity, quoted from the research page: “Schema draft, unvalidated. No structural or transmission-line PE has reviewed it. Insulator swing, pole capacity, crossarm span and guying are checked against the bulletin’s worked examples; ROW width and galloping are formula-consistency only.” Tension, wind and swing limit for each curve are the bulletin's TH-10 161 kV example values (no wind 4,633 lb, 16.4°; moderate 6 psf, 6,244 lb, 53.2°; high 12.5 psf, 10,400 lb, 77.7°; 800 ft horizontal span). The dashed marks at 1° and 2° are the angles where the bulletin prints worked values, such as 315.89 ft and 390.40 ft for the moderate case; this page's numbers agree with the Python within the ±2 ft its tests allow. The harness returns computed values, not verdicts.Real functions this maps to:
required_vertical_span_ft, conductor_wind_load_per_foot.Not modeled: the clearance the swing limits protect (Bulletin Table 7-1) and whether any span is acceptable, which stays a caller comparison. A negative value from Eq. 7-3 (the no-wind curve at 0°) is the raw formula result and is shown as computed. Conductor and string are fixed to the worked example's 795 kcmil 26/7 ACSR and 135 lb string; temperature, ice, sag and the backswing case are not modeled. This is a canned sweep of three fixed cases, not a design chart for your line.See also:Insulator swing, interactive · Pole groundline moment, auto sweep