The constant $K$ is taken from the 'Electric Cables Handbook', 3rd Edition, BICC Cables, 1997.

Symbol
$K_{\mathrm{BICC}}$
Unit
-
Related
$n_{\mathrm{cw}}$
Used in
$X_{\mathrm{0}}$
Choices
Number of wiresconstant K
10.05
30.0778
60.0678
70.0642
120.0617
150.0599
180.0584
190.0544
300.0545
340.0535
350.0533
370.0528
470.0522
530.0519
580.0516
610.0514
910.0512
1270.051
1690.0507
2170.0504
2710.0501