Effect of bow tie tree on PE and XLPE insulation

Among the water tree phenomena occurring in polyethylene (PE) and crosslinked polyethylene (XLPE) insulation, a bow tie tree phenomenon occuring from micro voids (less than 10 μm) in polymer was the subject of our research. Bow tie tree inception mechanism and its behavior was examined by model simulation test using a miniature cable. The results of this experiment proved that the bow tie tree inception and propagation was related to the oxidation reaction in the polymer. Based on this fact, the water tree endurance of XLPE using various curing agents and additives was measured in a “sheet” model test. The test revealed that bow tie tree occurrence would be greatly affected by the oxidation stability of the polymer and the rigidity of molecular linkage of the polymer.