Second Tier: International Top-Level (Scientific Research, Arbitration-Level Applications) Megger (UK) - FRAX Series Status: The originator of global FRA technology, with the highest data authority. Features: Extremely high measurement repeatability and stability, commonly used in multinational projects, dispute arbitration, or top-level scientific research laboratories. Expensive, software logic biased towards European and American standards. Doble (USA) Features: Closely integrated with dielectric loss testing, providing comprehensive insulation diagnostic solutions. HIOKI (Japan) Features: Known for high precision and high sensitivity, suitable for precision small transformers or laboratory research. 5. Typical Application Scenarios Diagnosis after Short Circuit Impact: After a transformer suffers an outgoing short circuit current impact, it must be tested immediately to determine whether the winding has displaced or deformed. Acceptance after Transportation and Installation: After long-distance transportation or hoisting of large transformers, check whether the internal structure is damaged. Comparison before and after Overhaul: Test before and after core lifting maintenance to verify the maintenance effect and reset condition. Routine Condition Monitoring: Include in the annual preventive test plan, establish a long-term trend archive, and detect looseness or slow deformation early. 6. Key Points for Operation and Data Analysis Wiring Consistency: This is the most critical factor. The wiring method (terminal lead length, grounding position, tap changer position) for each test must be exactly the same as the original record; otherwise, curve differences may be caused by “false deformation” due to wiring. Temperature Correction: Changes in oil temperature affect the dielectric constant of the oil, thereby affecting the high-frequency curve. High-end instruments have temperature compensation functions, or tests need to be conducted at similar oil temperatures. Criteria: Correlation coefficient R > 0.95: Generally considered no deformation. 0.90 < R < 0.95: Possible slight deformation, requiring comprehensive judgment combined with other tests (such as short-circuit impedance, no-load current). R < 0.90: Highly likely significant deformation, recommended to perform core lifting inspection. (Note: Specific thresholds should refer to DL/T 911 standard and manufacturer recommendations) Three-Phase Horizontal Comparison: For newly commissioned transformers or those without historical data, using the symmetry of the three-phase structure to compare A/B/C phase curves is an effective preliminary judgment method. 7. Purchase Recommendation Summary Routine Maintenance (110kV and below): Choose standard models from Wuhan Extra High Voltage or Yangzhou Huimin, with high cost performance, simple operation, fully meeting national standards. High Voltage/Extra High Voltage Main Transformers (220kV and above) or Scientific Research: First choice is the high-end AI version of Wuhan Extra High Voltage or Megger FRAX, focusing on its anti-interference capability, three-phase synchronization function, and accuracy of intelligent diagnostic reports. Special Requirements: If integration with online monitoring systems is needed, confirm whether the instrument supports specific communication protocols
