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Partial discharge test has been widely used as an effective means of defect detection in AC system, but the partial discharge detection test method of DC cable is still in its infancy. In order to determine the field test voltage of DC partial discharge detection, the relationship between DC test voltage amplitude and air gap defect detection rate of ±320 kV cable prefabricated terminal was studied in this paper. Taking the air gap defect commonly existing on the composite interface of ±320 kV cable prefabricated terminal as the research object, we calculated the maximum electric field intensity in the air gap through multi physical field simulation, and whether the defect may produce partial discharge was judged by the electric field intensity exceeding the threshold. Based on the probability and statistical analysis, the partial discharge probability density function of cable joints under the condition of considering random factors such as cable operating temperature and air gap position was established, and the function equation between defect detection rate and ambient temperature and DC test voltage was presented. The results show that the function equation between the detection rate of air gap defect at the cable interface and the ambient temperature and DC partial discharge test voltage conforms to the fourth power function, and the detection rate increases with the increase of ambient temperature. If the DC test voltage is 1.85U0, the detection rate is 99.25% at 20℃, and the detection rate can reach 99.85% at 30℃. The DC test voltag amplitude can be determined by the function equation.
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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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