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Inductance
Inductance (L): The property of a circuit or circuit element that opposes a change in current flow.
Inductance thus causes current changes to lag behind voltage changes. Inductance is measured in
henries (H). Inductance per core of a 3 core cable or of three single core cables comprises two
parts, self inductance of the conductor and the mutual inductance with the other cores.
For energy cables
L = K + 0.2 *log e(2S / d ) (mH/km)
where
K = constant relating to the conductor formulation
Number of wires in conductor
K (50Hz)
1
0.0500
3
0.0778
7
0.0642
19
0.0554
37
0.0528
61 and over
0.0514
S = Axial spacing between conductors within the cable, or
Axial spacing between conductors in a trefoil group, or
1.26 x phase spacing for a flat formation of 3 single core cables
0.5 x pcd of neutral screen for single core neutral screen cables (mm).
d = conductor diameter (or for shaped designs, the diameter of an equivalent circular conductor
(mm).
REACTANCE (Inductive Reactance)
.
X = 2 *π* f*L (Ω /km)
where
f = Frequency (Hz)
L = Inductance (mH/km)
10.3.3.1
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