Charge Behavior In MgO/PE Nanocomposite Under High Electric Field

Polymer nanocomposite materials have been attracting much attention as a new material because the properties of the original material can be drastically improved by adding a few percent of nano-sized filler. It has been found that nano-sized MgO-filler added into crosslink polyethylene (XLPE), which had been developed for HVDC cable insulation, improved the dc breakdown property of conventional XLPE cable.In this paper, recent topics and their important results will be reviewed on electrical properties of polymer nanocomposite materials. A multi-core model proposed by Toshikatsu Tanaka is discussed to understand various properties and phenomena in nanocomposite.At first, to investigate the influence of MgO nano-filler on space charge properties, we measured the space charge distributions using pulsed electro-acoustic method (PEA) system under DC electric field. In the case of LDPE with nano-filler, there is less space charge injection than LDPE.Also, we measured the trap depth of conventional XLPE and MgO/XLPE by using a photo-stimulated discharge system. We did not find PSD current in MgO/XLPE. Space charge is expected to be closely related to the nature of carrier traps.Finally, electric field dependence, time variations and the spectra of Electroluminescence (EL) pulses were examined. As the results of these experiments, the addition of MgO nanoparticles in XLPE matrix makes elevate the EL inception level and decrease the number of EL pulses. The EL spectra is different between XLPE and MgO/XLPE.