- The insulation of proper thickness over the conductor is provided in order to prevent leakage current.
- The leakage current is a current which flows in a path that don’t intend to provide to it. As the conductor is circular, the path of leakage current is radial.
Let us
- Radius of the single core conductor of cable = r1
- Internal sheath radius = r2
- Length of cable = L
- Resistivity of cable insulation = ρ
Let us consider very small thickness of insulation dx
at radius x distance.
- Area of leakage current flows = 2πxL
- Length through leakage current flows = dx
- Insulation resistance of layer dx = ρ ( dx / 2πxL )
Insulation resistance of cable
R α ( 1 / L )
- The insulation resistance is inversely proportional to length of cable. If the length of cable decreases, its insulation resistance increases and vice versa.
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