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Inductance of a cable consist of two parts:
The BICC Electric Cables Handbook, give the formuale for inductance as:
L=( K+0.2ln 2S d )× 10 −6
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
The reactance of a conductor is given by:
X - reactance in Ω.m-1
L i indcutance in H.m-1
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:
x - reactance per metre of conductors, mΩ.m-1
Xc - reactance of conductor, mΩ