Space charge in XLPE power cable under dc electrical stress andheat treatment

It is well known that the existence and accumulation of space charge in insulation can be harmful to polymer power cable. Although there is much research done on space charge distribution in various samples, there are still some important problems left unsolved, such as the mechanism of formation and elimination of space charge in dielectrics. Because of its superiority, the pulsed electro-acoustic (PEA) measurement method is used widely in the measurement of space charge in various geometries of samples such as the multiple layer plate and cylindrical cables. The space charge in crosslinked polyethylene (XLPE) power cable under dc voltage and heat treatment is investigated by the PEA method in this paper. After heat treatment, the space charge, which previously formed in cable insulation under the applied voltage, disappears. 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 dc voltage is applied to the cable, no more space charge will be formed in the cable. The mechanism of formation and elimination of space charge under the effect of electrical and thermal stress is discussed