The effect of Surface Traps on the Interfacial Charge Dynamics in Layered Dielectrics

Space charge is a matter of concern in HVDC applications, causing considerable stress enhancement and consequent degradation. Apart from space charge within the volume of the insulation, interfacial charge at a multidielectric interface further aggravates the stress. The difference in permittivity and conductivity of the different dielectrics used in a composite insulation system are primarily responsible for interfacial charge. However, surface conditions and trap characteristics at the dielectric-dielectric interface have a significant role to play, and neglecting these effects would lead to erroneous estimation of interfacial charge, and poor insulation design. Hence, an improved charge transport model is proposed in this paper to model the charge dynamics at dielectric-dielectric interfaces. The effect of surface traps on a $300 \mu \mathrm{m}2$-layer LDPE is studied through space charge data obtained from Pulsed Electro Acoustic (PEA) measurements.