Electrical tree is a common type of insulation deterioration in power cables. The growth of electrical trees will change the performance of insulating materials, thereby threatening the safe operation of cables. However, traditional detection methods are often unable to realize effective detection of the tiny electrical trees deteriorated area in cable. A 10 kV single-core cross-linked polyethylene (XLPE) was selected, and electrical tree defects were introduced into its insulation. The insulation conductivity and equivalent capacitance between the inner and outer semiconducting layers at different growth stages of electrical trees were measured, and the electrical trees deteriorated area was tested and located by broadband impedance spectroscopy and inverse Fourier transform method. The results show that the growth of electrical trees increases the conduction current of the cable insulation significantly. The increase of electrical tree cumulative damage makes the capacitance value between the inner and outer semiconducting layers increase. Due to the change of conductivity and capacitance, the wave impedance of the electrical tree deteriorated area distorts. Using the broadband impedance spectroscopy and inverse Fourier transform methods can realize the accurate location of the electrical tree deteriorated area. At the same time, the different growth stages of electrical tree will significantly affect the amplitude of distortion points in the impedance spectroscopy and inverse Fourier transform spectrum.
| 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 |