Investigations on the Effect of DC Conductivity on AC Dielectric Behaviour of Polymeric Insulation

When subjected to alternating current (AC) fields, a dielectric behaves predominantly as a capacitor and thus permittivity decides the field distribution. Also, the presence of an imaginary component of permittivity, which is closely related to the so-called AC conductivity, causes dielectric loss and thus heating. In addition, there is always a direct current (DC) conductivity component which causes dielectric heating, whose magnitude may be around 4 to 5 orders less than its AC counterpart and thus usually ignored under AC. In this paper, the authors investigate the effect of incorporation of both AC and DC conductivity in context of polymeric cable insulation under different scenarios and interesting inferences are drawn.