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To study the internal relationship between space charge transport and polarization/depolarization current of cross-linked polyethylene (XLPE) cable insulation in direct current (DC) field, a space charge-current combined measurement platform was established based on PEA method. The combined measurements were conducted on XLPE cable insulation samples with different ageing time. Parameters such as total charge, carrier mobility, and trap distribution in XLPE samples were evaluated using the combined variation data of space charge and current. The results show that at room temperature and 20 kV/mm, homopolar charges accumulation occurs obviously within the sample, and with the increase of test temperature; the charge polarity changes to the opposite. With the increase of ageing time, the number of accumulated heteropolar charges in the aged samples increases at first and then decreases, and the range of positive charge accumulation expands from near the anode to near the cathode; the decay rates of polarization and depolarization currents in the aged samples decrease, the steady value of polarization current increases, and the depolarization current increases at first and then decreases. With the increase of ageing time, the total amount of charge within the samples increases at first and then decreases, while the conductivity and carrier mobility increase. Notably, the carrier mobility significantly increases when the samples are ageing for more than 10 days, causing the charge accumulation range to gradually extend further from the anode, resulting in a significant reduction in the total amount of accumulated charges within the samples. The trap depth of XLPE samples increases gradually with the increase of ageing time, which is the reason for the reduced decay rate of depolarization current in the aged samples.
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| 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 |
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