Partial Discharge Behaviors in High Voltage Cable Buffer Layer

In recent years, the buffer layer faults of HV XLPE cable have seriously affected the secure and stable operation of power grid. At present, it is found that the failure is related to the electric field distribution in buffer layer. Moreover, the partial discharge (PD) occurs in the buffer layer due to the electric field distortion, which eventually leads to ablation. In this work, in order to investigate relationship between fault and partial discharge, the PD test under long-term AC voltage is established according to the actual structure of cable buffer layer. During the measurement the partial discharge characteristic parameters are recorded. Based on the statistical characteristic the whole process of PD experiment is divided into four stages: initial stage, develop stage, stagnation stage and pre-breakdown stage. The PD activities in each stage have different features, which reflects in statistical characteristics. It is found that almost all statistical characteristics of PD are the maximum value in pre-breakdown stage. Furthermore, the discharge current is over 20 mA in the pre-breakdown stage and consequently the discharge ablation traces are formed during the measurement. All conclusions imply that the partial discharge is a vital cause of ablation.