Electric characteristics of MgO/LDPE nanocomposite up to breakdown under DC ramp voltage

To understand DC breakdown phenomena of low density polyethylene (LDPE) mixed with nano-sized magnesium oxide (MgO), the electric properties, namely, DC breakdown strength, conduction current, space charge formation and local heat generation up to the breakdown under increasing field with a particular rate of increase was investigated. DC breakdown strength of nanocomposite was found to be high compared to that of LDPE. The increasing rate of the conduction current in nanocomoposite with respect to the average field (under high field) was suppressed by the addition of MgO nano-filler. The space charge formation and the local heat generation were also suppressed under high field. From these results, it is suggested that the suppression effect of conduction current affected by the space charge led to higher DC breakdown strength of nanocomposite material.