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To solve the problem that it is difficult to diagnose the moisture defects of cable joints with the existing methods, this paper proposes a method for diagnosing the moisture defects of cable joints based on frequency modulated continuous wave (FMCW) and time reversal (TR). Firstly, a distributed parameter model of cable was established. The FMCW method was employed to capture multi-frequency reflected signals from impedance mismatches at defects and joints. These inversion signals were injected into a test cable model to derive an energy curve, and the energy curve is served as a diagnostic spectrum for cable defects. Subsequently, the impedance discontinuity point detection was carried out for the simulation cable models with different end-loads and intermediate joints. Finally, joint defect diagnosis was carried out for the real 750 m 10 kV power cable and 2 km 10 kV power cable. The results show that the method proposed in this paper can not only accurately determine the location and characteristic of the impedance discontinuity points in cable, but also improve the distance resolution of the defect location peak. The joint positioning peaks of "positive first and then negative" and "negative first and then positive" can respectively represent normal and damp cable joints. Therefore, the method proposed in this paper can accurately detect the moisture defects of cable joints and has a good engineering application prospect.
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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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