261 / 2022-03-14 22:37:24

Study on Heating Characteristics of Water Tree Defect in XLPE Cable

XLPE Cable,Water trees,heating characteristics,distributed temperature measuring devices,defect detection

The present work studied the heating characteristics of water tree in XLPE cable through simulation, and discussed the feasibility of detecting water tree by detecting the heating of cable.

XLPE samples with a thickness of 5 mm were aged by the water-needle method with the voltage of 6 kV/5 kHz. After accelerated water tree aging for 600h, the cultivated water trees with the average width of 384.22 μm and average length of 548.36 μm were observed in the anatomical sections of the samples. The finite element simulation model was established based on the measured sizes of water trees, and the microstructure of the model was following the pearl string model. The simulation calculated the heating of the cable under conditions of growing water tree size and gradual water penetration.

The simulation results revealed that under the operating conditions of a 110kV cable, the temperature in the water tree area was significantly higher than that in the original XLPE area, and the maximum temperature difference reached about 6 °C. With the development of the water tree and the penetration of water, the temperature of the defective part will further increase. If distributed temperature measuring devices are arranged outside the outer semi-conducting layer, a temperature rise of 2 °C can be detected at the position with the thinnest residual insulation thickness.

Therefore, for 110kV cables, the existence and development of water trees can lead to local temperature rise. By arranging distributed temperature measuring devices outside the outer semiconducting layer, the location and development of water tree defects can be calibrated by observing the increase of temperature.