Dry-type Transformer: What Happens To The Windings When A System Short Circuit Occurs?

In the daily operation of power systems, sudden incidents often test the resilience of core equipment. For dry transformer equipment, external short-circuit faults pose an extremely destructive challenge. When such extreme situations occur, a massive energy surge erupts instantly within the equipment, directly threatening the structural safety of core components.

The Intense Interplay Between Magnetic Fields and Current

During a system short circuit, the windings experience enormous electrodynamic forces, stemming from the interaction between the short-circuit current and the leakage magnetic field. The instantaneous short-circuit current can typically reach tens of times the rated value. Since the electrodynamic force is proportional to the square of the current, the impact force on the windings increases exponentially.

• Radial Force Impact: The radial force on the high-voltage winding expands outward, while the low-voltage winding experiences inward compressive force. If the mechanical strength of the windings is insufficient, the coils may disintegrate or flatten.

• Axial Force Imbalance: The longitudinal component of the leakage magnetic field generates axial forces, attempting to pull the windings apart at both ends or compress them inward, leading to loosening of the spacers or even misalignment of the coils.

The Chain Reaction of Physical Damage

Short circuits cause more than just a jump in current; they also put the mechanical structure to its limits.

Mechanical Deformation and Displacement

If the instantaneous surge of electrodynamic force exceeds the yield strength of the winding support structure, the coil will undergo irreversible physical deformation. This deformation may be difficult to detect in the early stages, but it will change the reactance value of dry type transformer manufacturers, creating potential problems for subsequent operation.

The Fatal Threat to the Insulation Layer

During severe vibration and displacement, the inter-turn insulation material is easily damaged by friction or compression. Once the insulation structure is damaged, the risk of partial discharge or even direct breakdown increases sharply, ultimately shortening the equipment's lifespan.

Strategies to Improve Short-Circuit Resistance

To cope with these uncontrollable external impacts, modern 750 kva dry type transformer equipment requires precise numerical simulation to assess stress distribution during the design phase. Selecting high-strength electromagnetic wire and optimizing the winding end fastening structure can give the equipment greater resilience when facing sudden electrodynamic forces. Strengthening the control of the support material ensures that the winding maintains spatial displacement stability under immense pressure.