Abstract：To understand a self-healing phenomenon during accelerating water tree aging, the self- healing mechanism of water tree is investigated in this paper. A water-needle electrode method is used to accelerate water tree aging. The dielectric loss factor of the cable samples increases with the aging time, but gradually returns to a lower level when the applied voltage is removed and a self- healing phenomenon appears. A water tree model with a series of water-filled micro voids and channels is built. According to the calculation of the electric field distribution by the finite element method (FEM), the electric field strength at the tip of the water tree is significantly enhanced when the micro channels are open, and the mechanical stress generated by the electric field exceeds the elastic limits of the XLPE, which leads to the formation of the new water-filled micro voids and the growth of water tree. However,it appears elastic recovery within the water tree channels without the applied electric field, and the water is squeezed out to the channels and many channels are closed, which results in the dielectric loss factor decreased and a self-healing phenomenon. The electric field strength at the top of micro cavities and the closed micro channel is significantly enhanced when the voltage is applied again. Eventually, all the water tree channels are gradually opened. The studies show that the self-healing and the open of the channels are a gradual process and the time mainly depends on the electric field strength and yield strength of the insulation.
赵威, 周凯, 刘凡, 杨琳, 刘曦. 在XLPE电缆加速老化过程中理解水树的自愈性[J]. 电工技术学报, 2014, 29(6): 311-317.
Zhao Wei , Zhou Kai , Liu Fan , Yang Lin , Liu Xi. Understanding Self-Healing of Water Tree in Process of Accelerated Aging of XLPE Cables. Transactions of China Electrotechnical Society, 2014, 29(6): 311-317.
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