Space charge behaviors and trap distributions of polypropylene/polyolefin elastomer blend under different elongation ratios

Polypropylene (PP) blended with polyolefin elastomer (POE) has been considered as a potential choice to replace XLPE as HVDC cable insulating material. During the process of fabrication, installation, and operation, the cable insulating material may be exposed to mechanical stress. In order to study the effect of mechanical stretching on the safe operation of cables, PP/POE blends were prepared and stretched to different ratios, and the space charge behaviors were measured by a pulsed electro-acoustic (PEA) method. Besides, the trap distribution was obtained based on the surface potential decay test. The results indicate that mechanical stretching can promote the space charge accumulation and migration in PP/POE blends. With the elongation ratio increasing from 1 to 1.2, the density of shallow traps increases, while both the depth and density of deep traps decrease. However, an opposite phenomenon can be observed when the elongation ratio increases from 1.2 to 1.4. The microstructure changes of the PP/POE blend due to mechanical stretching is considered to be responsible for the change in space charge behaviors and trap distributions. © 2017, High Voltage Engineering Editorial Department of CEPRI. All right reserved.