Water treeing degradation under combined mechanical and electricalstresses

摘要

The authors present results of experiments in which LDPE(low-density polyethylene) and/or XLPE (cross-linked polyethylene)specimens were subjected to mechanical vibrations in water or tomechanical vibrations and electric stress combined. Water tree growthexperiments in stretched films of XLPE cable insulation are alsodescribed. Attempts to grow water trees by application of vibrationalmechanical stresses to polyethylene immersed in water or containingcavities filled with water were unsuccessful. Vibrational mechanicalstresses of moderate amplitude applied to the insulation together withelectric stress do not change the water tree growth rates as comparedwith the insulation subjected to electric stress only. Static tensilestresses enhance the growth of vented water trees but have no effect onbow-tie trees. However, the effect is significant up to 30% strain only