INSULATION RESISTANCE
Siechem
Wires & Cables
Insulation resistance is the alternating current resistance between two electrical
conductors and the insulating material. In the electric cable, the value of the resistance
between the conductor and the earthed core screen, metallic sheath, armour or adjacent
conductors.
Consider a unit length of single-core cable with conductor radius 'r' and radius
over insulation 'R'. The surface area of a ring of insulation of radial thickness 'ox ' at
radius 'x 'is 2rr x times the unit length.
%
The insulation resistance oR of the ring is
oR= pox
2.izx
The insulation resistance of the radial thickness 'R-r' for a cable length T is DR
D =
P log
R
Where
II 21lf e r
DR=Insulation resistance of the cable (f.l)
p = the specific resistivity (f.lm)
For XLPE is 1x 1
0l4.
For PVC is 1x 1
013.
= length of the cable (m)
R = Radius of the cable (mm)
R = Radius of the conductor (mm)