Characteristics of Space Charge Accumulation in Polypropylene-Based Insulating Materials under DC Stress

We have been investigating the insulating property of polymeric materials, especially polyethylene (PE) based materials, for power transmission cables under extra high AC and DC stresses. In this study, using a simultaneous measuring system for space charge distribution and external circuit current, we attempted to evaluate the properties of polypropylene (PP) based polymers, which are expected to apply to an insulating material for dc power transmission cable. As the results, we found that large amount of space charges accumulated were observed in some of PP and PE copolymers at high temperature under high dc stresses, while any charge accumulation was not observed at room temperature under the high dc stresses.