SPACE-CHARGE IN XLPE POWER CABLE UNDER DC ELECTRICAL STRESS AND HEAT-TREATMENT

It is well known that the existence and accumulation of space charge i n insulation can be harmful to polymer power cable. Although there is much research done on space charge distribution in various samples, th ere are still some important problems left unsolved, such as the mecha nism of formation and elimination of space charge in dielectrics. Beca use of its superiority, the pulsed electro-acoustic (PEA) measurement method recently is used widely in the measurement of space charge in v arious geometries of samples such as the multiple layer plate and cyli ndrical cables. The space charge in crosslinked polyethylene (XLPE) po wer cable under de voltage and heat treatment is investigated by the P EA method in this paper. After heat treatment, the space charge, which previously formed in cable insulation under the applied voltage, disa ppears. If electrical stress is applied to the insulation again, space charge will appear once more. However, after the cable is heated and degassed in vacuum for a long time, no matter how long the de voltage is applied to the cable, no more space charge will be formed in the ca ble, The mechanism of formation and elimination of space charge under the effect of electrical and thermal stress is discussed.