Effect of Moisture on the Electrical Treeing Characteristics in ER and ERIP

Epoxy resin (ER) and epoxy resin impregnated paper (ERIP) are commonly used insulation materials, playing important roles in the field of power equipment and electrical equipment. However, moisture has a significant impact on ER and ERIP insulation performance. To research the effect of moisture on the electrical treeing characteristics in ER and ERIP, the experimental platform of treeing at AC-temperature was established. The needle electrodes were cast into the samples with the gap of 2 mm. Electrical treeing experiments were conducted on moist and non-moist ER, ERIP samples at 16 kV AC at 60°C respectively. The results show moisture has little effect on the initiation of electrical trees. For the EP samples, the moisture results that the breakdown time of samples reduces. For the ERIP samples, the moisture prompted the morphology of the trees changing from branch like to bush like, which rarely occurring in the ERIP samples. The density of the trees increases and the fractal dimension increases significantly. The samples do not breakdown for more than 10 h. This may be due to the shielding effect of the defects. The results of this paper may help to explore the life of insulating materials and may provide a reference for the optimal design of insulation materials.