Parabolic approximation for distribution spans. Select conductor, enter span and tension, and calculate mid-span sag at any temperature. Results include a NESC clearance check for common crossing types.
Fills weight and RBS automatically
From ACSR/AAC tables — loaded condition
Used to auto-calculate initial tension
Horizontal distance pole-to-pole
Use span = ruling span for single spans
Horizontal tension at initial stringing temp
Typical: 60°F (15.5°C)
Max operating temp: 167–212°F for ACSR
Height where conductor ties to insulator
Difference from attachment grade — use 0 for level
📐 Sag Profile — Mid-span Cross-section View
Blue = initial stringing condition | Orange = calculated temperature condition | Green dashed = required NESC clearance (road crossing)
🌡 Sag at Multiple Temperatures
Temperature (°F)
Sag (ft)
Sag (in)
Clearance at Mid-span (ft)
Clearance vs. Road (18 ft min)
⚖ NESC Table 232-1 Clearance Check — At Calculated Temperature
⚠ Values per NESC 2023. Always verify against current edition, state PUC rules, and your utility's construction standards. These are minimum clearances — add design margin.
Crossing / Location
NESC Min. (ft)
Your Clearance (ft)
Status
Attach Height Needed
📐 Formulas Used
Parabolic Sag (industry approximation for distribution spans)
Sag at initial conditions:D₀ = w × L² / (8 × H₀)
w = conductor unit weight (lb/ft) | L = span (ft) | H₀ = initial horizontal tension (lbs)
Conductor length at initial conditions:S₀ ≈ L + 8D₀² / (3L)
This is the change-of-conductor-length method. For multi-span lines, substitute the ruling span for L in the thermal expansion step.
Sag at any point along span:y(x) = (4 × D × x × (L−x)) / L²
x = distance from attachment (0 to L) | D = mid-span sag | Max sag occurs at x = L/2
Note on ruling span: In a multi-span section, all spans share the same horizontal tension (assuming level attachments). The ruling span (RS) is the equivalent single span that produces the same tension as the multi-span section: RS = √(Σ(L³)/Σ(L)). For thermal calculations, the conductor expands based on the ruling span and redistributes tension equally across all spans. Always use the ruling span for temperature sag corrections, then use the actual span for final sag values.