Trapping parameters comparison between cable sections from different service conditions by a new trapping-detrapping model

Space charge formation will cause electric field enhancement at certain location in the polymeric materials, especially under HVDC insulation condition. In our previous works, a model has been developed which is suitable for analysing the space charge data from depolarization test to calculate the material trapping parameters. In the present paper, two cross-linked polyethylene (XLPE) cables, taken from HVAC service condition of 220kV for 12 years and for 8 years, were peeled as 100-200μm films from the outer to inner layer of insulation. Through the comparison between trapping parameters estimated from our model, it has been found that samples from inner insulation layers for both cables have the deepest trap depth and the greatest deep trap density, indicating samples from inner layers have the severest ageing.