Insulation Hazard Investigation: How To Deal With Uneven Electric Field Distribution Inside Dry-type Transformers

In routine maintenance of power systems, abnormal noises or localized overheating generated by the operation of cast coil transformer devices often point to a core technical issue: an imbalance in the internal electric field distribution. Under long-term high-load operation, this phenomenon directly induces performance degradation in insulation materials.

Air Gap Risk in High-Voltage Windings of Dry-Type Transformers

The accumulation pattern of charge at the interface of heterogeneous dielectrics determines the voltage distribution. cast resin distribution transformer primarily relies on epoxy resin and air as the insulating medium. Because the dielectric constant of air is much lower than that of epoxy resin, under the same voltage, air bubbles remaining inside the resin will experience a higher voltage gradient. This high concentration of charge in these tiny spaces is a breeding ground for partial discharge.

Specific Manifestations of Air Gap Discharge

• Sudden Change in Dielectric Electric Field: When holes exist within the insulation layer, the voltage will jump in that area.

• Ozone Erosion: The chemical reaction generated by the discharge corrodes the surrounding solid insulation, forming carbonized channels.

The Influence of Metal Sharp Corners on the Electric Field Distribution of Dry-Type Transformers

The physical morphology of structural components plays a decisive role in the direction of charge. Burrs or sharp edges at winding lead joints, taps, or fasteners will cause charge to rapidly accumulate in these extremely small radius areas.

• Tip effect analysis: Physical models show that the smaller the radius of curvature of a conductor, the higher the charge density near its surface.

• Floating potential phenomenon: Metal parts that are not properly grounded will generate induced voltage under a strong electric field, causing a sudden increase in the electric field difference between them and adjacent components.

Practical suggestions for optimizing the internal electric field strength of dry-type transformers

Improving the electric field environment requires starting with adjusting the physical structure. For equipment already in use, regular partial discharge testing is a direct way to monitor the insulation status.

Application of Shielding Structures

Installing an electrostatic shielding ring at the end of a high-voltage coil can smooth out the originally steep voltage gradient. This structure guides the charge to distribute evenly over a wider surface area by changing the physical boundaries.

Environmental humidity control

Increased air humidity significantly reduces the breakdown voltage of the air gap. Controlling the dryness of the installation environment is crucial for maintaining the stability of the cast resin dry type transformer manufacturers insulation system. Especially during the restart phase after a shutdown, condensation adhering to the winding surface can create a highly threatening discharge path.