Blue Electrical Charge Was Observed Near The Bushing Of The Dry-type Transformer!

A blue glow around a dry type transformer bushing is caused by corona discharge, a localized ionization of air that occurs when the electrical stress exceeds the breakdown strength of the surrounding insulation. This phenomenon indicates surface contamination, sharp conductor edges, or insulation degradation, requiring immediate inspection to prevent total dielectric failure.

Key Triggers of Corona in Distribution Networks

In a dry type distribution transformer, localized voltage stress ionizes the surrounding air molecules. This chemical reaction generates ozone and ultraviolet light, which manifests as a visible blue aura during low-light conditions.

Operating Triggers

• Environmental Pollution: Accumulation of dust, salt, or moisture on the bushing surface.

• Insulation Imperfections: Micro-voids within a dry cell transformer casting that trap air.

• Structural Wear: Degraded seals or loosened mechanical connections over time.

Risk Escalation in High-Capacity Systems

The severity of corona damage scales with the size of the electrical footprint. In a standard 1000 kva dry type transformer, persistent ionization slowly erodes the resin insulation, leading to micro-fractures and localized tracking along the bushing exterior.

For critical infrastructure utilizing a 2500 kva dry type transformer, this degradation accelerates significantly due to higher thermal and electrical loads, drastically increasing the risk of catastrophic phase-to-ground faults.

Resolution Protocol

1. Schedule Thermal Imaging: Use infrared and ultraviolet corona cameras to map the exact intensity and location of the discharge.

2. Execute Deep Cleaning: De-energize the unit and clean the bushings with specialized solvents to remove conductive surface films.

3. Install Electric Field Grading: Retrofit the terminals with corona rings to redistribute electrical stress away from sharp geometries.