Inductance of a cable consist of two parts:
- the self-inductance of the conductor
- the mutual inductance between conductors
BICC Electrical Cables Handbook
The BICC Electric Cables Handbook, give the formuale for inductance as:
where:
L - cable inductance, H.m-1
K - conductor formation constant
S - axial spacing between conductors within a cable, mm
- axial spacing between condcutors in trefoil, mm
- 1.26 x phase spacing of flat formation conductors, mm
d - condcutor diamters, mm
For 2, 3 or 4-core circular or sector-shaped cables, multiply the above by 1.02 to obtain the inductance. Multiply by 0.97 for 3-core oval conductors.
Typical values of K
Number of wire in conductor |
K |
1 (solid) |
0.0500 |
3 |
0.0778 |
7 |
0.0642 |
19 |
0.0554 |
37 |
0.0528 |
61 and over |
0.0514 |
Reactance
The reactance of a conductor is given by:
where:
X - reactance in Ω.m-1
L i indcutance in H.m-1
CENELEC CLC/TR 50480
Equations for inductance are given by CENELEC CLC/TR 50480 "Determination of cross-sectional area of conductors and selection of protective devices".
Three-line or line to line:
Line to neutral:
where:
x - reactance per metre of conductors, mΩ.m-1
Xc - reactance of conductor, mΩ
XcN -
XcPE -
XcPEN -
IEC 60909
See Impedance