有限元法电缆水树老化机理研究

Study of the XLPE Cables Water-Tree Aging Mechanism Based on the Finite Element Method

采用有限元法对水树起始机理进行了分析研究。有限元分析结果显示:XLPE绝缘内的局部微观缺陷导致电场畸变,水分积累形成椭圆水珠,对周围绝缘一起产生交变Maxwell应力作用,导致材料疲劳断裂。随着疲劳断裂的发展及水分的积累,逐渐发展形成相互连接的充水微孔和细枝,并最终发展形成水树。水树形成后,水树尖端电场畸变,当水树发展到一定长度或受到过电压作用,就会发展形成电树,并导致绝缘击穿。针对水树老化问题,提出了一些抑制和处理水树老化问题的方法和建议。

XLPE cables water-tree aging mechanism is analyzed by the finite element method（ FEM）. The analysis results show that： microscopic defects inside the insulation lead to the electric field distortion and cause the accumulation of the moisture to form ellipsoid water droplets. which together apply the alternating Maxwell stress for the arounding insulator and resulting in fatigue fracture. Under the Maxwell stress,plenty of water-filled branches and viods caused by fatigue fracture interconnected together and eventually to form the water tree. When the water tree grows to a certain extent or been subjected to an impact voltage would develop an electrical tree and cause the breakdown. In order to solve the water tree aging problem,the paper concludes some methods and recommendations to inhibit and effectively deal with the aged cables.