Space charge in polymeric insulation under ac electric fields — A schematic model

The effect of space charge on electrical performance of polymeric insulating materials under ac conditions has not been fully recognized. This paper intends to make people understand the importance of space charge under ac conditions. Based on growing evidences of the presence of space charge at power frequency and charge carrier characteristics observed under dc conditions, a schematic model has been proposed to explain why negative charges are always observed in the material when subjected to ac electric fields. Furthermore, features of ac space charge dynamics and its potential impact on electrical performance of dielectric materials have been described.