Study on Partial Discharge of Metal Particles in XLPE Cable Terminal Excited by X-Ray
Zheng Shusheng1, Kong Ju1, Dai Minting1, Liu Zhichao1, Zhang Zongheng2, Wu Shiyou3
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources; North China Electric Power University Beijing 102206 China; 2. Chengde Power Supply Company State Grid Jibei Electric Power Co. Ltd Chengde 067000 China; 3. Nanchang Power Supply Branch of State Grid Jiangxi Electric Power Corporation Nanchang 330069 China
Abstract：The discharge signal of small metal particle defect in cable terminal is weak, and the sensitivity of traditional partial discharge detection method is constrained. Recently, The method of using X-ray to excite the internal air gap of solid insulation to produce partial discharge has been applied in engineering. Different from the single air gap defect, the cable metal particle defect has both metal and air gap coexisting. It will aggravate the electric field distortion at the defect. On the other hand, the metal can supply initial electrons via field emission, surface photoelectric emission. The impact of X-ray on the partial discharge of such defect is unclear. To address these issues, this paper proposes a method of using X-ray to excite the partial discharge of metal particle defect in cable terminal, and the feasibility of the method is verified by experiments. Firstly, partial discharge measurement experiments under X-ray irradiation were conducted on metal particle defects with different electric field distributions and different sizes on the cable terminal simulation model. The effects of X-ray on the partial discharge inception voltage, discharge repetition rate and apparent discharge amount of defect were analyzed. Secondly, the X-ray tube voltage was varied to investigate changes in the discharge characteristics of the defect under different intensities of X-ray irradiation. Thirdly, the influence mechanism of X-ray on the partial discharge of metal particle defect was analyzed in terms of discharge inception field strength and initial electrons. Finally, the feasibility of the proposed method was tested on a 10 kV cable terminal. The test results show that X-ray irradiation can reduce the partial discharge inception voltage for metal particle defect with different electric field distributions and different sizes, with the reduction range from 11.4% to 29.3%. Compared with no X-ray, X-ray irradiation can increase the discharge repetition rate of metal particle defect, with an increase of 36.1%~725.9%. X-ray has no significant effect on the apparent discharge magnitude of metal particle defect. The excitation impact on the number of defect partial discharge becomes increasingly evident with increasing X-ray intensity. The calculation results of photoelectron yield of different media under X-ray irradiation show that the interaction between X-ray and gas molecules is the main source of initial electrons, and X-ray can stimulate the defect to generate discharge under the condition of satisfying the field strength of discharge onset. For the 10 kV cable terminal defect model, X-ray can reduce its partial discharge incpetion voltage and increase the discharge repetition rate. The following conclusions can be drawn from the experiment results: (1) X-ray have an excitation effect on the partial discharge of metal particle defect at the cable terminal. It can be used to improve the detection efficiency of partial discharge of metal particle defect in cable. (2) The presence of a tiny air gap in the defect of metal particles is responsible for the X-ray's excitation impact on discharge. (3) X-ray intensity has a significant effect on the effectiveness of defect partial discharge excitation.
郑书生, 孔举, 戴敏婷, 刘志超, 张宗衡, 吴诗优. X射线激励XLPE电缆终端金属颗粒局部放电的研究[J]. 电工技术学报, 2025, 40(3): 913-927.
Zheng Shusheng, Kong Ju, Dai Minting, Liu Zhichao, Zhang Zongheng, Wu Shiyou. Study on Partial Discharge of Metal Particles in XLPE Cable Terminal Excited by X-Ray. Transactions of China Electrotechnical Society, 2025, 40(3): 913-927.
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