The effects of space charge on conduction mechanism in polymer dielectric-air gap structure

We have analyzed the effect of space charge on conduction current in LDPE with an air gap structure by employing the modified PEA (Pulsed-Electrode Acoustic) method to suggest a new conduction mechanism in the dielectric-air gap structure. This method enables one to measure simultaneously the space charge and conduction current. The results show that the conduction mechanism is SCLC (Space Charge Limited Current) type irrespective of the partial discharge in the air-gap. The conduction current increased or deceased abruptly when LDPE is exposed to high voltage for a long time. This repeated between high level and low level without periodicity because of the preformed space charge in the air gap.