# What additional factors need to be considered when calculating voltage drop?

Considering the following formulas for voltage drop, what additional factors need to be included and how can resistance be derived to thoroughly calculate theoretical voltage drop for multiple scenarios?

For example, cables run in steel conduit will need to be treated differently than cables run in 'free space' (this falls under resistance but is additional to cable resistance). The National Electric Code contains resistance & impedance data but only for specific scenarios and cable ratings.

How can one cover all necessary factors in the absence of raw data in order to produce an accurate result? Or, how can one obtain the data if it exists?

1. DC: Vd = $$\2IRL\$$

2. Single phase: Vd = $$\2IZL\$$

3. Three phase: Vd = $$\\sqrt{3}ZL\$$

• Please feel free to correct the formatting of the formulas. – Lott99 Jul 1 at 22:50