In order to investigate the impact of thermal ageing on the development of DC partial discharge of surface scratched cross-linked polyethylene (XLPE) cables, a surface scratched defect model weas made using a physical 10 kV cable, and subjected to the accelerated thermal ageing treatments with different times. The partial discharge characteristics of defective cables under DC voltage were studied using the pulse current method. On basis of the variation of partial discharge with voltage applying time, the statistical charts of the maximum discharge capacity, average discharges capcity, and discharge repetition rate in different discharge intervals were extracted. Then based on the charge transport theory, partial discharge and charge transport models were proposed to explain the partial discharge results of defective cable. The results show that the initial partial discharge voltage of the defective cable increases with the increase of thermal ageing time, the discharge quantity-time spectrum shows "comb" discharge characteristics. As the thermal ageing time increases, the average discharge capacity and discharge repetition rate of the defective cable in the interval greater than 100 pC decrease gradually, and the “comb" discharge characteristics disappear completely after 21 days of ageing, demonstrating the self-healing ability of partial discharge. During thermal ageing, the surface oxidation of XLPE scratched defects produces charge traps, resulting in a uniform and dense space charge layer, which reduces the internal electric field of the defects and weakens partial discharge in defective cables. The research results provide data support for the study of DC partial discharge of XLPE cable defects.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |