1. Structural composition of oil-immersed transformer
1. The iron core is the magnetic circuit part of the transformer. During operation, hysteresis losses and eddy current losses will occur. In order to reduce heat loss, the core is composed of cold-rolled grain-oriented silicon steel sheets with high magnetic permeability less than 0.35mm. According to the winding arrangement in the iron core, there are iron core type and iron shell type.
In large-capacity transformers, in order to ensure that the heat lost in the iron core can be fully taken away by the circulating insulating oil, and in order to achieve a good cooling effect, cooling oil channels are often set up in the iron core.
2. The winding and core are the core components of the transformer. Since the winding itself has resistance or contact resistance at the junction, I2Rt knows that heat is generated. Short-circuit current will produce large electromagnetic force on the winding and damage the transformer. The basic windings are concentric type and overlapping type.
3. The main faults of transformer windings are inter-turn short circuit and short circuit to the shell. Inter-turn short circuit is mainly due to insulation aging, or mechanical damage to the insulation through short circuit due to overload of the transformer. The oil level in the transformer drops, causing the winding to expose the oil surface, and inter-turn short circuits may also occur; when a short circuit passes, the windings are deformed due to the overcurrent effect, causing mechanical damage to the insulation, and inter-turn short circuits may also occur. The current in the short-circuited winding may exceed the rated value, but the current in the entire winding must not exceed the rated value. The cause of the shell short circuit is also due to aging of insulation or moisture in the oil, or due to lightning strikes and operating overvoltage. In addition, if a cross short circuit occurs,
Due to overcurrent and winding deformation, a short circuit will also occur to the casing. When the shell is short-circuited, the gas protective device and the grounding protection are usually activated.
4. The oil-immersed transformer body is installed in an oil tank filled with transformer oil. The oil tank is welded with steel plates. The oil tank of small and medium-sized transformers consists of a tank shell and a tank cover. If the box cover is opened, the box can be lifted out for maintenance.
| oil immersed power transformer |
| oil immersed self cooled transformer |
