Reduction of AC-breakdown strength due to particle inclusions in XLPE cable insulation

Addition of conducting iron and copper particles to XLPE power cable insulation reduced the short term AC breakdown strength from 107 kV/mm to 70 kV/mm and 35 kV/mm, for spherically and irregularly shaped particles respectively. In case of objects containing glass particles, the breakdown strength was reduced to 55 kV/mm, regardless of the shape of the particle. Addition of either 2,3 weight % acetophenone or cumylalcohol to objects containing 10 irregularly shaped iron particles increased the AC breakdown strength from 30% to about 80% of that of degassed reference objects without particles. Thus impregnation significantly reduces the detrimental effect of particles