## Inductance & Reactance

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:

$L=\left(K+0.2\mathrm{ln}\frac{2S}{d}\right)\times {10}^{-6}$

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:

$X=2\pi fL$

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

Three-line or line to line:

Line to neutral:

where:

*x* - reactance per metre of conductors, mΩ.m^{-1}

*X _{c}* - reactance of conductor, mΩ

*X*-

_{cN}*X*-

_{cPE}*X*-

_{cPEN}

## IEC 60909

See Impedance