Method for Measuring Leakage Current in LDPE Insulated Miniature Cables Containing Volatile Additives at Elevated Temperatures

A method for measuring leakage current in LDPE insulated miniature cables containing volatile additives is presented. It is shown that with the presented method the volatiles are sufficiently contained in the test object even at temperatures up to 90 °C. This is achieved through non permeable encapsulation around the outer insulation screen (extruded semiconducting layer). Guard electrodes are adopted on either side of the measuring electrode to eliminate the effect of surface currents on the terminations. The method is useful for indirectly relating the content of individual peroxide decomposition products to the leakage current in XLPE based HVDC cables. Evaluation of the method was performed using acetophenone that was soaked into the test objects prior to encapsulation. After heat treatments at up to 90 °C the acetophenone content of the samples were investigated. This was done by consecutive HPLC and weight loss measurements. Data from two-hour conductivity measurements using this method are presented and a clear influence of acetophenone is observed at 30, 70 and 90 °C.