Handling Transformer Insulation Damage And Maintenance Cycles

Proper management of insulation damage is critical to ensuring transformer longevity and grid stability. Below are key preventive and corrective measures:

1. Preventive Maintenance

   • Leak Detection: Regularly inspect for oil leaks and ensure no water accumulation exists in the transformer body to prevent moisture/air ingress.
   • Breather System: Maintain proper oil level in the breather seal and ensure desiccant (e.g., silica gel) remains dry (blue indicates dry; pink indicates saturation).
   • Explosion-Proof Components: Verify the integrity of the explosion-proof membrane and pressure relief valve to prevent air ingress, which could degrade oil insulation.

2. Oil Quality Management

   • Oil Replenishment: Use only qualified oil for topping up, and avoid filling from the tank bottom to prevent impurities (e.g., metal particles) from entering the core.
   • Gas Analysis: If the light gas protection activates, promptly analyze gas composition via chromatography to identify internal faults.
   • Oil Sampling: Secure oil sampling port bolts after maintenance to prevent leaks.

3. Temperature Monitoring

   • Critical Parameters: Closely monitor winding and top-oil temperatures. If nearing alarm thresholds (e.g., 80°C for alarms, 100°C for shutdown), adjust load and cooling systems immediately.
   • Forced-Oil Transformers: Reduce load promptly if top-oil temperature rise exceeds limits to avoid accelerated insulation aging.

4. Fault Response

   • Post-Trip Procedures: Immediately stop the oil pump after a fault trip to prevent contaminants from spreading to unaffected areas.
   • Overload Management: Strictly control overload duration and prioritize load reduction to mitigate thermal stress on insulation.

Maintenance is categorized into major overhauls (requiring core lifting or tank opening) and minor inspections (external checks/oil processing).

Per DL/T573-2010 "Guidelines for Maintenance of Power Transformers":

1. Standard Interval: 10+ years for major overhauls, unless:
   • Early Intervention: Required due to faults, abnormal preventive test results, or structural vulnerabilities (e.g., short-circuit impacts).
   • Sealed Transformers: Major repairs only needed for severe oil leaks or confirmed internal faults.
2. On-Load Tap Changer (OLTC): Overhaul after reaching manufacturer-specified operation counts or upon detecting defects.

1. Frequency: Every 1–3 years, with increased frequency for transformers in polluted environments.
2. Scope: External inspections, oil topping, and oil purification without core lifting.

1. Routine Inspections:
   • Check oil level, leaks, bushing integrity, and terminal temperatures.
   • Monitor oil flow indicators and ensure submersible pumps operate continuously.
2. Surge Protection:
   • Record surge arrester activation events and inspect transformers post-operation.
3. System Redundancy:
   • Avoid running transformers without light gas protection; temporary deactivation requires strict protocols and immediate reinstatement.

By adhering to these guidelines, operators can minimize insulation failures, optimize maintenance schedules, and ensure safe, efficient transformer operation.