Ruling Span

Conductor ruling span is used to simplify the calculation of conductor tension and sag. It represents a hypothetical uniform span length that approximates the mechanical behavior of an entire section of a powerline, accounting for variations in individual span lengths and loading conditions.

By assuming uniform properties, the ruling span allows engineers to design powerlines efficiently while ensuring structural reliability and maintaining proper clearance from the ground or obstacles.

This method is particularly useful for analysing the impact of environmental factors like wind and ice on conductor performance.

Ruling Span L_R ✅

L_R = \sqrt{\dfrac{\text{sum of cubes of span length}}{\text{sum of span lengths}}}

L_R = \sqrt{\dfrac{(L_1)^3 + (L_2)^3 + (L_3)^3 + ...}{L_1 + L_2 + L_3 + ...}}

Where:

• L_R = ruling span length (m)
• L_x = span length (m)

Example

Span lengths

L_1 = 100 \text{m}

L_2 = 150 \text{m}

L_3 = 200 \text{m}

Calculation

L_R = \sqrt{\dfrac{(L_1)^3 + (L_2)^3 + (L_3)^3}{L_1 + L_2 + L_3}}

L_R = \sqrt{\dfrac{(100)^3 + (150)^3 + (200)^3}{100 + 150 + 200}}

L_R = \sqrt{\dfrac{1,000,000 + 3,375,000 + 8,000,000}{100 + 150 + 200}}

L_R = \sqrt{\dfrac{12,375,000}{450}}

L_R = \sqrt{27,500}

L_R = 165.83 \text{m}