During the normal operation of converter transformer, moisture will cause the decline of the electrical performance of oil-paper insulation and accelerate its ageing, resulting in a decrease of life and insulation breakdown. In order to study the influence of moisture on the space charge characteristics and breakdown characteristics of oil-paper insulation under AC and DC composite voltage, we prepared oil-paper insulation samples with different water content, then we used space charge measurement under AC and DC composite voltage to get the influence of moisture content on the space charge characteristics of oil-paper insulation under the voltage forms of AC, DC, and AC and DC composite voltage, and studied the breakdown characteristics of samples with different moisture contents under different voltage types. The results show that the electric field distortion rate of oil-paper insulation under AC and DC composite voltage is greater than that under DC and under AC electric field; as the DC component increases, the increase amplitude of breakdown voltage of the samples with higher water content is significantly lower than that of samples with lower water content, and the electric strength of samples with low water content is more affected by the DC voltage component than that of samples with high water content.
| 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 |