Study on the dielectric response characteristic of XLPE cables

As a key factor of insulation deterioration of XLPE cables, water tree can lead to the decrease of insulation property. But the dielectric loss caused by water tree is obvious at a very low frequency due to the long-time polarization of internal space charge. In this paper, focused on the dielectric response of cables, the dielectric loss spectrum of cable samples is also calculated by employing the extended Debye approach. Then the results are compared to measurements of dissipation factor (tan δ) at different frequencies by IDAX206, which shows that the aged cable has higher values of dielectric loss than a new one. The paper studies how the dielectric loss data can be effectively used to determine ageing state of the cables' insulation.