What is the formula to calculate Ruling Span?

The formula for calculating Ruling Span is essential for determining the span of conductors used in overhead power lines to ensure proper tensions and structural integrity. The correct formula involves taking the Average Span and then adding two-thirds (2/3) of the difference between the Maximum Span and the Average Span.

This calculation accounts for the variations in span lengths and their impact on the overall design and reliability of the power line. By starting with the Average Span, which represents a typical distance between support structures, and then adjusting it by adding a portion of the difference to account for the extremes of span lengths, you arrive at a more representative Ruling Span. This approach helps mitigate risks of sag and tension issues that can occur in lines with uneven spacing.

The other options provided either misrepresent the relationship between the average and maximum spans or fail to account for the adjustment necessary to arrive at a conservative estimate of the span required for safe and effective operation of the system. Hence, the choice of combining the Average Span with an adjustment based on the Maximum Span and the Average Span provides a practical and effective approach for lineman professionals.