Grundfos SP Series Installation And Operating Instructions Manual page 449

Example:
U = 3 x 415 V
I = 100 A
L = 150 m
U = 3 %
150
L

Lx = ------- - = --------- - = 50 m = q 50 mm
U
3 %
U = 3 x 415 V
I = 100 A
U = 3
%
L = 150 m
2
449