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Dry-type transformer windings are directly exposed to the air, and are highly susceptible to interlayer short-circuit faults due to environmental factors such as temperature and humidity. Moreover, the early insulation degradation is difficult to detect. Therefore, this paper aims to investigate the electromagnetic characteristics of winding interlayer insulation faults, providing a theoretical basis for optimal insulation configuration and condition diagnosis. First, an interlayer short-circuit current testing method using dry-type transformer taps was proposed, and a 3D "field-circuit" coupled model consistent with actual transformer dimensions was established for experimental validation. Subsequently, based on the temperature-humidity-resistance correlation characteristics of insulation materials, a parametric model was established for winding interlayer insulation resistance. The evolution laws of fault-layer current and spatial magnetic flux density under different fault locations were simulated and analyzed during the insulation resistance decay process from 106 Ω to 0 Ω. The results show that the fault layer current and magnetic flux density exhibit a non-linear and highly sensitive response to the changes in interlayer insulation resistance. When the insulation resistance drops to 103 Ω and 10 Ω, respectively, the electromagnetic parameters undergo significant abrupt changes, and the change rates of fault layer current and magnetic flux density increase to 12.55 A/Ω, 0.01 mT/Ω, and 66.69 A/Ω, 14.65 mT/Ω, respectively. Furthermore, after the interlayer insulation resistance decreases to 10 Ω, as the fault location moves from the outer to the inner layer, the fault layer current and spatial magnetic field first increase and then decrease, and presenting a spatial distribution pattern of "maximum in the center, minimum at the edges". On the basis of these abrupt change characteristics, 103 Ω and 10 Ω are determined as the critical resistance criteria for interlayer insulation degradation and breakdown of winding layers in dry-type transformers, respectively. According to their spatial distribution characteristics of current and magnetic field under interlayer insulation fault, it is concluded that the middle layer of the winding is the area with weak insulation, while the edge layer is the area where fault detection is unfavorable.
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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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