Power Knowledge | What is an Electrical Transformer? How to Prevent Its Failures?

Classification of High-Voltage Tests for Electrical Transformers

• Characteristic Tests: These primarily involve testing the main circuit contact resistance of circuit breakers, ampere-voltage curves, GIS (Gas Insulated Switchgear) characteristics, polarity, etc., for electrical transformers and other equipment.
• Insulation Tests: These are further divided into destructive tests and non-destructive tests:
  • Destructive Tests: Include high-voltage withstand tests (e.g., DC and AC withstand tests). While these tests are effective for detecting equipment defects due to their high voltage, they carry the risk of damaging the equipment’s insulation, potentially reducing its service life.
  • Non-destructive Tests: Use non-destructive methods to identify overall defects in electrical equipment. Although they operate at lower voltages and have lower sensitivity, they are more commonly used in practice due to their safety.

Safety Measures Before High-Voltage Testing of Transformers

1. Site Safety Precautions:
   • Hang warning signs and set up safety nets around the testing area to keep bystanders away and prevent personal injury.
   • Assign personnel to monitor the site and prevent unauthorized access, ensuring the safety of both testers and outsiders.
2. Personnel Competency:
   • High-voltage testing requires high technical expertise. Ensure that all staff involved have adequate professional skills and overall quality.
   • Brief each worker on the specific risks of their assigned tasks before the test, so they can take appropriate safety precautions and remain vigilant during the process.
3. Wiring Inspection:
   • Since wiring is often assigned to less experienced staff, conduct a comprehensive inspection of all connections to prevent errors that could affect the test or cause safety hazards.

Modern Protection Solutions: Transformer Online Monitoring System

• Partial discharge inside the transformer
• Bushing dielectric loss and capacitance
• General transformer performance parameters (e.g., line current, on-load tap changer status, winding temperature)
• Oil chromatogram analysis

• PDSCOPE: For partial discharge data acquisition and analysis
• TD GUARD3: For online monitoring of bushing dielectric loss and capacitance
• EDS MK3: For general transformer performance monitoring (e.g., current, tap changer, temperature)
• DGA: For oil chromatogram monitoring

Conclusion