Causes Of Short Circuit In Oil Filled Power Transformer

In many cases, the damage of oil filled power transformer is caused by short circuits. The causes of short-circuit damage to oil-immersed transformers are different and complicated. Today, the editor of our transformer manufacturer will introduce to you the reasons for the short circuit damage of oil-immersed transformers:

1) After multiple external short-circuit impacts, the deformation of the coil is gradually serious, and the final insulation breakdown is mostly damaged;

2) The exterior is frequently damaged by short-circuit impact in a short time;

3) Damaged by long-term short-circuit impact;

4) Damaged by one short-circuit impact.

The main form of transformer short-circuit damage

According to the situation that the transformer is damaged due to the short-circuit of the outlet in recent years, when the oil filled power transformer is short-circuited, the damage mainly has the following characteristics and causes.

3.1 Axial instability

This kind of damage is mainly caused by the axial electromagnetic force generated by the radial leakage flux, which causes the axial deformation of the transformer winding, and this type of accident accounts for 52.9% of the entire damage accident.

3.1.1 Up and down bending deformation of wire cake

This damage is due to the permanent deformation of the wire between the two axial spacers due to the excessive bending moment under the action of the axial electromagnetic force. Usually, the deformation between the two cakes is symmetrical.

3.1.2 Collapse of winding or wire cake

This damage is due to the fact that the wires are squeezed or collided with each other under the action of axial force, resulting in oblique deformation. If the wire is slightly inclined at the beginning, the axial force will increase the inclination, and it will collapse in severe cases; the larger the ratio of the height to the width of the wire, the more likely it will cause collapse.

In addition to the axial component, the end leakage magnetic field also has a radial component. The combined electromagnetic force generated by the leakage magnetic field in the two directions causes the inner winding wire to turn inward and the outer winding to turn outward.

3.1.3 Lift the winding to spread the pressure plate

This damage is often due to excessive axial force or the presence of insufficient strength, rigidity or defective assembly of its end supports.

3.2 Radial instability

This damage is mainly caused by radial electromagnetic force generated by axial flux leakage, resulting in radial deformation of oil filled power transformer windings, accounting for 41.2% of the entire damage accident.