1) Multiple external short-circuit surges gradually cause coil deformation, with most resulting in insulation breakdown and damage.
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
Due to the damage to transformers caused by export short circuits in recent years, the main characteristics and causes of transformer damage during short-circuit faults are as follows.
3.1 Axial Instability
This type of damage is primarily caused by the axial electromagnetic force generated by radial flux leakage, leading to axial deformation of the transformer winding, accounting for 52.9% of all damage incidents.
3.1.1 Linear Cake warping and deformation
This damage is caused by the wire between the two axial bushes undergoing plastic deformation due to excessive bending moments under the action of the axial electromagnetic force, typically resulting in symmetrical deformation between the two bushes.
3.1.2 Winding or cake collapse
This damage is due to the wires being compressed or impacted under axial forces, leading to tilting deformation. If the wires are originally slightly tilted, the axial force promotes further tilting, which can result in collapse under severe conditions; the greater the height-to-width ratio of the wires, the more prone to collapse they become.
In addition to the axial component, there is also a radial component in the end leakage magnetic field. The composite electromagnetic force produced 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 damage is primarily caused by the radial electromagnetic force generated by the leakage flux in the axial direction, leading to radial deformation of the transformer winding, accounting for 41.2% of the total damage incidents.
3.2.1 Insulation damage due to elongation of the outer winding wire
Radial electromagnetic force attempts to enlarge the diameter of the outer winding, and excessive tensile stress on the wire can lead to plastic deformation. This deformation often results in wire insulation damage, causing inter-turn short circuits. In severe cases, it can lead to the coil collapsing into, or becoming tangled, and even fracturing.
3.2.2 Transformation of Winding End
In addition to the axial component, there is also a radial component of the end magnetic flux. The resultant electromagnetic force produced by the leakage flux in both directions causes the winding conductors to flip inward and the outer winding to flip outward.
