Simultaneous measurement of space charge distribution and external circuit current in XLPE under HVDC at high temperature

As a long distance DC power transmission cable, XLPE (cross-linked polyethylene) insulated cable is considered to be used. Since the cable is supposed to be used at high-temperature because a large current flows in inner conductor, it is necessary to estimate the performance of the insulating material at high temperature. Especially, characteristics of a space charge accumulation and a conduction current in the material under a high DC stress at high-temperature is important to estimate it. Therefore, it has been developed a measuring equipment which is enable to measure the space charge distribution and the external circuit current density simultaneously at high temperature. In this report, several typical measurement results, that are obtained using the developed system, will be introduced. As a result, it is found that the moving speed of the injected packet-like charge increases with increase of temperature. Furthermore, it is found that a current value significantly depends on the polarity of the applied voltage is generated.