In order to obtain the location information of defects in buffer layer of HV cable, at first, according to the surface morphological characteristics of buffer layer, the buffer layer states were devided into dry state, damp state, corroded state, and corroded-ablative state, and the change law of volume resistivity and relative dielectric constant during the development of defects from dry state to corroded-ablative state of buffer layer was studied via thin slice samples. Then the computing formula of the distributed capacitance and distributed conductance in the network of HV cables transmission line was derived. The feasibility of applying the FDR method to locate defects in the buffer layer of HV cables was also evaluated. Finally, a long cable experimental platform was built in the laboratory to study the effectiveness of the FDR method in locating buffer layer defects. The results show that the development of buffer layer defect mainly affects the distributed capacitance, and impedance discontinuity points generate in the process. FDR can locate the moisture and defects of the buffer layer, but the further distinction between corrosion defects and ablation defects needs to be combined with other state detection methods.
| 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 |