The insulation in a DC cable is subjected to both thermal and electric stress at the same time. Defects in insulation may cause a local overheating due to leakage currents. Calculate the electric current in the faulty insulation with small defective area.
A plane-parallel problem of DC conduction.
Electric conductivity of insulation γ - depends on temperature, as shown on the plot below;
Conductor potential U = 10 kV;
Shield potential U = 0 V;
Cable temperature T = 80 °C (353 K);
Local overheating Tmax = 120 °C (393 K).
Calculate the electric current in the insulation.
The model depth is taken as 10 cm (defect region length).
Leakage current, I
|1.24e-8 A (124 μA/km)|
Current density distribution in the insulation close to the thermal defect.