# Factor for cross-bonded earthing

This is the multiplication factor for cross-bonded earthing.

When the lengths of the three cable sections are not known, $p_{cb}$ should be set to 1, and $q_{cb}$ to 1.2, giving a value for $f_{cb}$ slightly below 0.004.

For two single core cross-bonded cables, which is not covered in the IEC standard, $f_{cb}$ is set to 0.004.

When all the lengths of the three cable sections are identical, $f_{cb}$ becomes zero.

Symbol
$f_{cb}$
Formulae
 $\frac{{p_{cb}}^2+{q_{cb}}^2+1-p_{cb}-p_{cb} q_{cb}-q_{cb}}{\left(p_{cb}+q_{cb}+1\right)^2}$ three-phase system $\frac{{p_{cb}}^2+1-p_{cb}}{\left(p_{cb}+1\right)^2}$ two-phase system $0$ single-phase system
Related
$a_{S1}$
$a_{S2}$
$a_{S3}$