Study on the electric-field characteristics of water tree region on the dry or wet condition in XLPE cables

To studies the relationship between the dielectric parameters and electric-field characteristics in water tree region in XLPE cables, liquid needle electrode and high-frequency high-pressure were used for water tree accelerated aging of XLPE cable samples, and the shapes of water trees were observed by microscope. Then a finite element simulation was constructed based on the shapes of water trees observed, and the influence of the dielectric parameters in water tree region on the electric field surrounding the water tree was analyzed by simulated calculation. The results show that the electric-field strength of water tree peripheral increases and the electric-field strength of tip decreases and the water tree peripherals can easily become the starting point for electrical trees, with the increasing of the dielectric constant and electrical conductivity of the water tree. On the contrary, with the decreasing of the dielectric constant and electrical conductivity of the water tree, the electric-field strength of tip increases and the electric-field strength of water tree peripheral decreases, and the tip can easily become the starting point for electrical trees.