(a) Derive the formula for the electric stress in a single core cable…

Question

(a) Derive the formula for the electric stress in a single core cable. Where the stress is maximum and where it is minimum?

(b) A $33\text{kv}$ 3-phase underground feeder, $3.4\text{km}$ long uses three single core cable. Each cable has a conductor diameter of $2.5\text{cm}$ and the radial thickness of insulation is $0.6\text{cm}$. The relative permittivity of dielectric is $3.1$. Find:

(i) Capacitance of the cable per phase

(ii) Charging current per phase

(iii) Total charging $\text{kVar}$

(iv) Dielectric loss per phase if the p.f of the unloaded cable is $0.03$.

(v) Maximum stress in the cable.