Causes Of Burning Out Of Three Phase Oil Immersed Transformer

We must use the three phase oil immersed transformer correctly, but the oil immersed transformer will also be damaged in use. There are many common failures of the oil immersed transformer. What are the reasons for the burning of the oil immersed transformer?

The oil immersed transformer is burnt out, which may be caused by the following reasons:

1. There are no fuses on both high and low voltage sides of the three phase oil immersed transformer. Although some of them have been installed with drop type fuses and sheep horn fuses, most of their fuses are replaced by aluminum or copper wires. As a result, when the low voltage is short circuited or overloaded, the fuses cannot fuse normally and burn the oil immersed transformer.

2. The high-voltage and low-voltage fuses of the oil immersed transformer are improperly configured, and the fuses on the oil immersed transformer are generally over configured. When it is seriously overloaded, the oil immersed transformer will be burned.

3. Because there are many lighting lines in rural areas, most of them use single-phase power supply, and the randomness of jumpers in construction and the inadequacy of management, the distribution and transformation loads operate in a biased phase. Due to long-term use, the insulation of a phase coil is aged and the oil immersed transformer is burned.

4. Tap changer:

(1) The tap changer of distribution transformer was adjusted without permission, causing the tap changer of distribution transformer not in place, poor contact and burning.

(2) Poor quality of tap changer causes incomplete contact of star contact position, short circuit or ground discharge.

5. Oil leakage is a common appearance abnormality of three phase oil immersed transformer. Since the body of the oil immersed transformer is full of oil, there are rubber beads and rubber pads at all connecting parts to prevent oil leakage. After a long time of operation, some rubber beads and rubber pads in the oil immersed transformer will age and crack, resulting in oil leakage. As a result, the performance of the insulation will deteriorate after being damp, the discharge will be short circuited, and the oil immersed transformer will be burned.

6. Most of the high-voltage and low-voltage lines of oil immersed transformers are introduced from overhead lines. Because the lightning arresters are not put into operation in time or are not installed with 10kV lightning arresters, the oil immersed transformers will be burned during lightning strikes.

7. Multi point grounding of iron core.

8. When the low-voltage side of the oil immersed transformer is short circuited to ground and between phases, a short-circuit current 20-30 times higher than the rated current will be generated. When such a large current acts on the high-voltage winding, a large mechanical stress will be generated inside the coil, which will lead to coil compression. After the short-circuit fault is removed, the stress will disappear. If the coil is repeatedly subjected to mechanical stress, its insulating rubber beads and rubber pads will loosen and fall off; The iron core clamp bolt will also be loose, and the high-voltage coil will be distorted or cracked. In addition, high temperature will also be generated, which will cause the oil immersed transformer to burn down in a very short time.

9. Man made damage:

(1) The outgoing line of the three phase oil immersed transformer is a copper screw, and the overhead line is usually an aluminum core rubber wire, which is easy to cause electrochemical corrosion between copper and aluminum.

(2) Bushing flashover discharge is also a common abnormal phenomenon in oil immersed transformers.

The above are the common causes of burning out of oil immersed transformers. Oil immersed transformers must find out the causes of burning out so that they can operate normally.