1) Multiple external short-circuit shocks cause the coil to deform progressively, with insulation breakdown and damage being the predominant issue.

2) Frequently damaged due to short-circuit shocks within a short period.

3) Damage due to long-term short-circuit surges

4) Damaged by a single short circuit surge.

3 Main Forms of Transformer Short Circuit Damage

In light of recent transformer damage incidents due to export short circuits, the following characteristics and causes of damage during short-circuit faults have been identified.

3.1 Axial Instability

This type of damage is primarily caused by the axial electromagnetic force generated by radial magnetic leakage, leading to the axial deformation of transformer windings, accounting for 52.9% of all damage incidents.

3.1.1 Linear cake bending and deformation

This damage is due to the wire between the two axial shims undergoing plastic deformation under the action of the axial electromagnetic force, caused by excessive bending moment. Typically, the deformation between the two shims is symmetrical.

3.1.2 Winding or bobbin collapse

This damage is due to the wires being compressed or impacted under axial force, resulting in tilt deformation. If the wires originally have a slight tilt, the axial force causes the tilt to increase, and in severe cases, they collapse; the greater the ratio of height to width of the wires, the more prone they are to collapse.

The end leakage magnetic field, in addition to the axial component, also includes a radial component. The combined electromagnetic force generated by the leakage magnetic field in both directions causes the inner winding conductors to flip inward and the outer winding conductors to flip outward.

3.1.3 Winding lifting will open the pressure plate

This damage is often due to excessive axial force, insufficient strength or rigidity of the end support components, or assembly defects.

3.2 Radial Instability

This type of damage is primarily caused by the radial electromagnetic force generated by the axial magnetic leakage, leading to radial deformation of the transformer windings, accounting for 41.2% of all damage incidents.

3.2.1 Extension of the insulated wire due to external winding causes insulation damage

Radial electromagnetic force attempts to increase the diameter of the outer winding, and excessive tensile stress on the wire can cause plastic deformation. This deformation often leads to insulation damage in the wire, causing inter-turn short circuits. In severe cases, it can result in the coil collapsing, winding out of place, and even breaking.

3.2.2 Transformation of Winding End

The end漏 magnetic field, in addition to the axial component, also has a radial component. The combined electromagnetic force produced by the leakage flux in both directions causes the winding conductors to flip inward and the outer winding to flip outward.