Space charge distribution measurement using PEA method-encounter with unexpected behavior-

Space charge accumulation phenomenon is one of key factor to resolve a problem to realize HVDC (High Voltage Direct Current) network, especially using a solid insulating materials. In the case of power transmission cable, it was hard to develop a good material for the insulating layer which was sustainable under DC high electric stress, and most of the cable using an ordinary insulating material like XLPE (cross linked polyethylene) couldn't pass a DC test for cable. The reason of such fail was thought as the accumulation of so-called space charge in the layer under high DC stress. To resolve such problem, authors have been investigating the space charge accumulation characteristics in various polymeric materials such as LDPE (low-density polyethylene), XLPE (cross-linked polyethylene) and modified materials based on polyethylene using PEA (pulsed electro-acoustic) method. From the measurement results, we have encountered many curious space charge behaviors which were not expected before the measurements. In this report, I would like to introduce these interesting characteristics of the space charge accumulation behaviors observed in the polymeric materials under high DC stress at various temperature.