Insulation-Resistance Rohit Damodaran

Siechem Wires & Cables INSULATION RESISTANCE Insulation resistance is the alternating current resistance between two electrical conductors and the insulating material. In the electric cable, the val ue 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 insula tion resistance =ofPthelorgadRial thickness 'R-r' for a cable length T is DR D II 21lf e r Where DR=Insulation resista nce of the cable (f.l) p = the specific resistivity (f.lm) For XLPE is 1x 10l4. For PVC is 1x 1013. = length of the cable (m) R = Radius of the cable (mm) R = Radius of the conductor (mm)