Dynamic conductive property and mechanism of buffer tape in HV XLPE cables

Ablation of the buffer layer in high voltage cross-linked polyethylene (XLPE) cables has been the attractive type of cable failure. The ablation of buffer layer commonly takes place under the pressure and moisture. Therefore, it is important to investigate the effect mechanism of pressure and moisture on the ablation of buffer layer. In this study, the simulated experiments of dry and wet water-blocking buffer tape under different pressures are carried out, whereby dynamic variations of current density, voltage and alternating current (AC) volume resistivity in the processes of ablation are obtained. The micromorphology of buffer tape specimens is obtained through the scanning electronic spectroscopy. It is shown that the AC volume resistivity of dry buffer tape samples gradually increases with time in the process of ablation, accompanied with the transient surge of current and the plunge of voltage. While the AC volume resistivity of wet buffer tape samples gradually decreases with time. Moreover, a decrease of AC volume resistivity occurs to the buffer tape samples after the water absorption. With the increase of pressure from 1.09 kPa to 5.45 kPa, a decrease of volume resistivity occurs to both the dry and wet buffer tape samples. Combined with the results of stimulated ablation experiments and the micromorphology of buffer tape, the effect mechanisms of the pressure and moisture on the conductive property of buffer tape are explained.