$$ V_d = \frac{2 \times L \times I \times R_{dc}}{1000} \quad \text{(simplified)} $$
A more accurate form for incorporates reactance ($X$): formula for cable size calculation
For a , the approximate voltage drop ($V_d$) is: $$ V_d = \frac{2 \times L \times I
$$ I_{rated} \ge I_{load} $$