Electroluminescence and dissipation current due to impulse superimposed on AC voltage in ldpe

LDPE is widely used as an insulating material for power cable. In order to clarify the conduction mechanism of LDPE under ac high field, the simultaneous observation of the dissipation current waveform and electroluminescence (EL) is carried out. As the results of experiments, it was found that when the EL was observed above the certain electric field, the dissipation current waveform became nonlinear and become to include the harmonic component. Power cable in service are inadvertently subjected to impulses generated by lightning and switching surges that are superimposed on the ac voltage at which they operate. Analysis of EL can help to clarify the degradation mechanisms that occur at points of electrical stress enhancement and lead to cable breakdown. Though the EL due to impulse voltage in XLPE has already reported by S.S. Bamji et.al., here it has been reported only the behavior of EL under various impulse voltage application by using needle-plane electrode system geometry. By using the film sample and three-terminal electrode system, the simultaneous observation of EL pulse number and dissipation current waveform due to impulse voltage superimposed on ac voltage in LDPE was carried out. From the results of experiments, it has confirmed that the EL properties due to impulse superimposed on ac voltage coincide with Bamji´s previous work. In this study, the relation between the dissipation current waveform and EL pulse due to impulse voltage superimposed on ac voltage will be discussed.