The oil-immersed transformer adopts a fully sealed structure, and the oil of the oil-immersed transformer is isolated from the air to slow down the change of the oil. Surface electrostatic spray, beautiful and anti-corrosion. Under the condition of serious overload, the insulation of oil-immersed transformer will not age, and it has excellent electrical and mechanical properties during use, ensuring that serious overload will not lead to oil aging. Transformer is mainly composed of iron core, winding, oil tank, oil conservator, insulation sleeve, tap changer and gas relay. Next, let’s take a look at the structural composition and characteristics of oil-immersed transformer.
I. Structural composition of oil-immersed transformer
1. The iron core is the magnetic circuit part of the transformer. During operation, hysteresis loss and eddy current loss will occur. In order to reduce heat loss, the core is composed of cold-rolled grain-oriented silicon steel sheets with high magnetic permeability of less than 0.35 mm. According to the winding arrangement in the iron core, there are iron core type and iron shell type.
In a large-capacity transformer, in order to make the heat lost by the iron core be fully taken away by the circulating insulating oil, and to achieve good cooling effect, the cooling oil channel is often set in the iron core.
2. Winding and iron core are the core components of transformer. Since the winding itself has resistance or contact resistance at the contact, I2Rt knows that heat is generated. Short-circuit current will produce a large electromagnetic force on the winding and damage the transformer. Basic windings are concentric and overlapping.
3. The main faults of transformer winding are turn-to-turn short circuit and shell short circuit. Turn-to-turn short circuit is mainly due to insulation aging, or mechanical damage to insulation caused by short circuit due to overload of transformer. The oil level in the transformer drops, which causes the winding to expose the oil level and turn-to-turn short circuit; When a short circuit passes through, the winding will be deformed due to overcurrent effect, which will cause mechanical damage to the insulation and turn-to-turn short circuit. The current in the short-circuit winding may exceed the rated value, but the current in the whole winding shall not exceed the rated value. The short circuit of the casing is also caused by insulation aging or oil moisture, or by lightning strike and operating overvoltage. Furthermore, if a cross short circuit occurs,
Due to over-current and winding deformation, the shell will also be short-circuited. When the shell is short-circuited, it is usually the action of gas protection device and grounding protection.
4. The oil-immersed transformer body is installed in an oil tank filled with transformer oil, and the oil tank is welded with steel plates. The oil tank of small and medium-sized transformer consists of box shell and box cover. If the box cover is opened, the box can be carried out for maintenance.
Second, the characteristics of oil-immersed transformer
Oil-immersed transformer adopts fully sealed structure, and the oil of oil-immersed transformer is isolated from air. Under the condition of serious overload, thermal breakdown has excellent electrical and mechanical properties during use. Redesign the oil tank to ensure that serious overload will not lead to oil aging.