DC cable mainly uses oil-paper and crosslinked polyethylene (XLPE) as insulation, and the conductivity characteristics of the two materials are different, which has a significant effect on the electric field distributions in cable. In this paper, a finite element model was established based on the 500 kV typical DC cable structure, and the thermal-electrical coupled simulation analyses were performed on the oil-paper and XLPE insulated cables. The electric field distribution characteristics in the two insulation under different temperatures and temperature drops were studied, and the influences of the conductivity temperature and electric field coefficient on the field strength distribution were analyzed. The conductivity variations of oil-paper and XLPE insulations among the same temperature and field ranges were compared. The results show that the electric field distribution in oil-paper insulation is affected by the insulation temperature difference in the electric field strength range of 10-25 kV/mm and temperature range of 20-90℃, and hardly changes with the insulation temperature under definite temperature difference, while the electric field distribution in XLPE insulation is affected by both insulation temperature and temperature difference. In addition, the overall conductivity of oil-paper insulation is higher than that of XLPE insulation, and its change amplitude with temperature and field strength is larger, which may be the reason why the electric field inversion in oil-paper cable insulation occurs at a lower temperature difference. For the insulating materials used in HVDC cables, the conductivity temperature coefficient should to be controlled small so as to reduce the temperature sensitivity.
| 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 |