Effect of Magnetic Field on Electrical Treeing Behavior in XLPE Cable Insulation

This paper presents study aimed at clarifying the effect of magnetic field on electrical tree propagation in crosslinked polyethylene (XLPE) cable insulation. By adding dicumyl peroxide (DCP) as cross-linking agent into low density polyethylene (LDPE), the test samples are made at cross-linking temperature (CT) ranged from 150 degrees C to 180 degrees C. The dimension of the sample is 20 mm x 20 mm x 4 mm. A pair of needle-plate electrode is employed to introduce electrical tree within the material. A DC magnetic field is placed perpendicular to the electric field, and the magnetic flux density (MFD) is set at 350 mT, 450 mT and 550 mT, respectively. By applying AC voltage between the electrodes, the tree is initiated from the needle tip and progressively propagates towards the grounded electrode. The morphology of the tree is captured by using a digital microscope, and the mean growth rate of tree length as well as tree width is calculated. Obtained results show that with the increase of the MFD, the tree morphology is varied from branch type to bush type. The mean growth rate is dependent upon the CT and is changed with the MFD. It is suggested that partial discharge activity within the tree channels is varied by the electro-magnetic force, and as a consequence the treeing behavior is altered.