Insulation Resistance of cable


Insulation Resistance of cable

The load current flows through the core of the cable whereas leakage current i.e., the current which is not useful flows from the conductor to the sheath through the dielectric material. The flow of leakage current is shown by dotted lines.
 The resistance of any material is given by

Where
 ρ is the specific resistance of the material
 l the length of the current path
 A is the cross section
Here dR represents the differential leakage resistance for unit length of the cable.






 we first write an expression for the insulation resistance of an annular cylinder with radii x and (x + dx) as measured from the centre of the core.


Where, the length of the cable is L unit the leakage resistance

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