Effect of Space Charge on Electrical Tree Initiation in XLPE/Voltage Stabilizer Composites Under AC Voltage

The space charge dynamic characteristic is a critical factor in electrical treeing under ac voltage, especially in the initiation stage. This article explains a method to analyze the effect of space charge on tree initiation. Crosslinked polyethylene (XLPE) composite samples with different contents of voltage stabilizer were prepared. The electrical tree inception voltage of each sample was measured with the needle-plate electrode. The space charge distribution characteristics of the composites were measured by a pulsed electroacoustic (PEA) system with an extremely fast pulse burst under ac. In addition, trap distribution characteristics were studied by the isothermal surface potential decay (ISPD) method. The results show that the voltage stabilizer inhibited tree initiation, and the optimum content was 0.5 wt%. The detected space charge near the electrodes decreased significantly from the voltage stabilizer, and the traps induced by the voltage stabilizer were inferred to be the main reason. In addition, it was confirmed that the calculated average bulk charge density had a negative correlation with the tree inception voltage, which could be a supporting datum for the ac tree initiation mechanism.