The distance rule of 10 feet plus 4 inches per 10 kV over 50 kV accounts for what?

• A. Weather
• B. Inadvertent movement
• C. Tool weight
• D. Noise

Answer: (B)

This rule focuses on providing a physical clearance that accounts for inadvertent movement toward energized parts. A baseline of ten feet establishes a broad safety margin, and the extra inches added for every 10 kV over 50 kV scale the distance as voltage increases because higher voltage creates a greater potential for arcing if a gap is reduced. The aim is to ensure that if a tool, piece of equipment, or worker shifts unexpectedly toward the energized conductor, there’s still enough space to prevent arcing or contact, reducing arc flash risk. Weather, tool weight, or noise don’t set this spacing; they aren’t the factor this calculation is designed to cover.