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Dielectric loss factor measurement is an effective means for detecting defects in capacitive electrical equipment. However, due to the limitation of the instrument power supply capacity, there are many difficulties in the application of high-capacitance equipment. The damped AC voltage method requires low power supply capacity, and the oscillation frequency can be adjusted to be close to the power frequency. However, the current dielectric loss factor measurement using this method is based on the waveform attenuation parameters of damped AC voltage, which is far less accurate than digital bridges and can only reflect particularly severe defects. Therefore, a method to measure the dielectric loss factor of high-capacitance equipment by using damped AC voltage combined with digital bridge was proposed in this paper. Firstly, a dielectric loss factor measurement system based on damped AC voltage was established. The dielectric loss factor was extracted by full-phase Fourier calculation. The dielectric loss factor measurement results of sinusoidal waves and damped AC voltage with different frequencies were compared, the difference between the two method were analyzed, and the correction method was proposed. Then, comparative tests were conducted on the cable samples aged in the laboratory and those exposed to water and moisture, as well as on-site 220 kV CVT, and the feasibility of dielectric loss factor measurement based on the damped AC voltage combined with digital bridges was verified. The results show that the absolute deviation between The absolute deviation between the measurement results of the measurement system established in this article under 50 Hz damping oscillation voltage and the measurement results of the standard dielectric loss measuring instrument is less than 0.1%, which can meet the requirements of engineering applications.
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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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